University of Groningen
Challenges in prenatal screening and diagnosis in the Netherlands
Bakker, Merel
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Challenges in
Prenatal Screening
and Diagnosis
in the Netherlands
Proefschrift
ter verkrijging van de graad van doctor
aan de Rijksuniversiteit Groningen
op gezag van
de rector magnificus, prof.dr. E. Sterken
en volgens besluit van het College voor Promoties.
De openbare verdediging zal plaatsvinden op
maandag 6 februari 2017 om 14.30 uur.
door
Merel Bakker
geboren op 10 augustus 1981
te Purmerend
Challenges in
Prenatal Screening
and Diagnosis
in the Netherlands
Promotor Prof. dr. C. M. Bilardo Copromotor Dr. E. Birnie Beoordelingscommissie Prof. dr. S. A. Scherjon Prof. dr. A. Ranchor Prof. dr. I. M. van Langen Prof. dr. O. B. Petersen
For Science
Per la Scienza
Colofon
Bakker, M.
Challenges in Prenatal Screening and Diagnosis in the Netherlands Dissertation University of Groningen
ISBN: 978-90-367-9297-4 (printed version) ISBN: 978-90-367-9296-7 (electronic version)
© 2016 M. Bakker. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanically, by photocopying, recording, or otherwise, without the written permission of the author. Design and lay-out: Niels de Rijk
Idea cover design: Merel Bakker (with premitted use of a photo made by Steven O’Connor MD, Pathologist Houston, Texas, USA) Printing: Ipskamp drukkers
chapter 1 General introduction
chapter 2 Low uptake of the combined test in the Netherlands – which
factors contribute?
Prenatal Diagnosis 2012 Dec; 32(13): 1305-12
chapter 3 Intra- and inter-operator reliability of manual and semiautomated
measurement of fetal nuchal translucency: a cross-sectional study Prenatal Diagnosis 2013 Dec; 33(13): 1264-71
chapter 4 Total pregnancy loss after chorionic villus sampling and
amnio-centesis in the Netherlands: a cohort study
Ultrasound Obstetrics & Gynecology. 2016 Jun 3. doi: 10.1002/uog.15986. [Epub ahead of print]
chapter 5 Increased nuchal translucency with normal karyotype and
anomaly scan: what next?
Best Practice & Research Clinical Obstetrics & Gynaecology 2014 Apr; 28(3): 355-66.
chapter 6 Targeted ultrasound examination and DNA testing for Noonan
syndrome, in fetuses with increased nuchal translucency and normal karyotype
Prenatal Diagnosis 2011 Sep; 31(9): 833-40
chapter 7 Prenasal thickness, prefrontal space ratio and other facial profile
markers in first trimester fetuses with aneuploidies, cleft palate and micrognathia
Fetal Diagnosis & Therapy, 2016 Nov 18. [Epub ahead of print]
chapter 8 Is 3D technique superior to 2D in Down syndrome screening?
Evaluation of six second and third trimester fetal profile markers Prenatal Diagnosis 2015 Mar; 35(3): 207-13.
chapter 9 General discussion and future perspectives chapter 10 English summary
Dutch summary
Appendix Abstracts
List of Publications Research Institute SHARE Curriculum Vitae Dankwoord 11 25 37 49 67 83 97 109 123 136 138 142 147 149 151 152
General introduction
1
General introduction
General introduction
M. Bakker
Prenatal screening in the Netherlands:
Introduction of a national screenings program
“Pregnancy care” consists of care around pregnancy and birth, starting already from the preconception period. During pregnancy future parents can opt for prenatal screening in order to let assess the risk of congenital anomalies in their fetus. A distinction should be made between prenatal screening in a low risk population and prenatal diagnosis in a high risk population. Prenatal screening does not give a definitive diagnosis but it gives an estimate of the probability that a fetal anomaly will be present. In contrast, prenatal diagnosis confirms or excludes the suspected problem in a pregnancy. Pregnant women may opt for prenatal diagnosis because in case of specific congenital anomalies (e.g. heart anomalies) it can be beneficial for the child to be born in a tertiary center, where postnatal care can be optimized for the baby. Alternatively, in case of congenital anoma-lies parents have the option of termination of the pregnancy.
In the Netherlands the national prenatal screenings program was introduced in Janu-ary 2007. This includes the combined test (CT) which is on average performed at around 12-13 weeks of gestation and the structural anomaly scan performed at around 20 weeks of gestation. As a consequence all pregnant women are nowadays asked during antenatal visit by their caregiver if they want to be informed about prenatal screening. Only if they opt to be informed they will be counseled by their midwife or gynaecologist, or rarely by the general practitioner. This set-up was chosen to guarantee the right of ‘not to know’. Based on the information provided, parents are expected to be able to make an informed choice on whether or not they want to opt for prenatal screening (RIVM).1
The 20 week anomaly scan was officially introduced as screening for neural tube de-fects, although women are informed beforehand that other structural anomalies can also be encountered.2 The uptake of this scan is high, more than 95 percent, which is
compa-rable to other European countries (RIVM 2011).
The CT is based on the measurement of the fetal nuchal translucency (NT, see Figure 1), maternal age and maternal serum markers (ß-HCG and PAPP-A) and has a detection rate of about 90% for a false positive rate of 5%.3,4,5,6-8 The CT was introduced initially as
risk-assessment for trisomy 21 only, but from May 2010 the screening was extended to include also trisomy 13 and 18.3 During this scan, besides chromosomal abnormalities,
non-chromosomal abnormalities can be found. Women/couples are not systematically informed about the possibility of finding structural abnormalities at the time of the CT. Nor are they informed that an enlarged NT can also be associated with structural abnor-malities, especially cardiac defects.
In contrast to the 20 week anomaly scan, the uptake of the CT in the Netherlands is low, around 25-30% and this varies among different regions. The CT uptake in recent years is even lower than the uptake of invasive prenatal diagnosis in women aged 36 or older before the national screenings program was introduced.9,10 A study performed in
the Netherlands before the advent of the national screening program and involving the offer of NT screening free of charge to pregnant women attending a number of commu-nity midwife practices, showed a much higher uptake of the CT i.e. 86%. The large major-ity of women, including those who declined the offer, were in favor of its standard offer.9
At the start of the national screenings program an age-related reimbursement policy was introduced for the CT: women aged 36 years and older had free access to the test whilst younger women had to pay approximately 150 euros. In contrast, all women had and still have free access to the structural anomaly scan. After a plea of professional orga-nizations to abolish this age-related access to prenatal screening, all women now have to pay for the CT.
The nuchal translucency plays an important role in prenatal screening. It consists of a subcutaneous accumulation of fluid behind the neck of the fetus and is generally visible by ultrasound between 11 and 14 weeks of gestation. The NT is part of normal develop-ment and its size is influenced by gestational age.11 It is considered abnormal only when
it exceeds a certain cut-off.3 Many different definitions and cut-offs for an increased NT
have been used in the past.12 Although debate continues as to which cut-off should be
used to offer further ultrasound investigation, the 95th or the 99th centile. Currently the second one (3.5 mm) is considered as an ultrasound abnormality. Measurement of the nuchal translucency is performed by certified and skilled sonographers, but it still remains a difficult measurement to perform accurately.13,14 To further improve the
detec-tion rate of trisomies, but especially to lower the false positive rate, the ductus venosus, tricuspid valve Doppler and the nasal bone were added in (1998-2001) as additional markers to the combined test.15-23
Once a high risk of a trisomy is found after the combined test (>1:200) or when there is suspicion of a structural anomaly, women are counseled for prenatal diagnosis. Whether or not they opt for prenatal diagnosis depends for most women on the procedure related risk.24
Figure 1 — Nuchal Translucency (NT)
1. LOW UPTAKE OF THE COMBINED TEST
Although the CT is offered to all the women in the Netherlands, its uptake is low, and varies among different regions, suggesting that possible cultural differences in attitude
towards Down syndrome and termination of pregnancy (TOP) may play a role.9,10,25
Furthermore, the difference in uptake in comparison with other European countries with a national screening program, such as Denmark (>90%) or with regional screening policies such as England and France (88%)26-29 is striking. In contrast to other
screen-ing policies, the aim of the Dutch prenatal screenscreen-ing is not to reach the highest uptake as possible, but to make sure that future parents make an informed decision regarding screening. So it is important to find out what possible reasons are for the low uptake of the CT in the Netherlands.
2. IMPROVING THE QUALITY OF THE NUCHAL TRANSLUCENCY MEASUREMENT
The NT is the most effective marker of trisomy 21 and is able to detect about 75-80% of the affected fetuses for a false positive rate of about 3-5%.6,7 Moreover, an enlarged NT
is associated with other chromosomal anomalies, genetic syndromes and structural anomalies.30 It is therefore important that the NT is measured precisely. The Fetal
Medi-cine Foundation (FMF) has developed international guidelines to promote a standardized measurement technique aimed at obtaining accurate manual NT measurements. Aim of the guideline is to achieve uniformity among different operators and guarantee a valid risk assessment.31 However, the acquirement of the correct midsagittal plane, the
selec-tion of the area containing the maximum NT and the placement of the calipers are still prone to error with the manual technique, which may compromise the performance of screening.13,14,32 Quality control programs performed in the setting of prenatal screening
indicate that some sonographers tend to underestimate the NT-measurements, probably trying unconsciously to avoid unfavorable risk assessment results. In this respect the introduction of a technical tool aimed at standardizing the NT measurement may reduce such a measurement error. In order to minimize variability in the measurement of the NT, a semi-automated NT measurement has been developed recently (sono-NT, GE Medi-cal Systems). Standardization through semi-automated measurement is thought to lower the standard deviation (SD) of the distribution of NT measurements, increase its preci-sion, and enhance the correct discrimination of normal from trisomic fetuses, especially when the operators are less experienced.33-35,36 However, it is not yet evaluated if possible
differences between the manual and semi-automated measurements are not only signifi-cant in terms of precision but also in terms of changing the individual risk status.
3. COUNSELING REGARDING THE RISK OF MISCARRIAGE AFTER INVASIVE PROCEDURES
Once an increased risk or an increased nuchal translucency is found during the com-bined test, women are counseled on the possibility of prenatal diagnostics. About 20-30% of the fetuses with an increased risk at the CT has a chromosomal abnormality.37 When
the NT is increased the presence of an abnormal karyotype varies from approximately 7% for a NT between the 95th and 99th centile (3.5 mm), to 20% for a NT of 3.5-4.4 mm, 50% for a NT of 5.5-6.4 mm, and 75% for a NT of 8.5 mm or more.37
After an increased risk parents are counseled and offered invasive prenatal diagnosis. One of the factors influencing women’s decision to opt for or decline chorionic villus sampling (CVS) or amniocentesis (AP) is the procedure related risk.24 Estimates of procedure related
fetal loss rates differ considerably in literature, varying from 0.5% to 1.0% or even more, for both CVS and AP.38-52 Most of these studies are cohort studies, have mixed populations
and are not recent. There are only a few randomized (controlled) trials. Tabor et al com-pared women undergoing an AP with a control group, showing a 1% higher fetal loss rate in women undergoing midtrimester amniocentesis.43 The fetal loss rate (FLR) following
CVS has never been compared in a randomized controlled trial (RCT) with a control group. The FLR of CVS has been compared to AP in a RCT and the procedure related risk was found comparable.42,44,48,53 When parents are counseled regarding the procedure related
risk of CVS or AP, most often 1% (or 1:100) is quoted according to the study of Tabor et al.54
It remains a challenge to estimate and report realistic valid risk figures from ‘real life’ cohort studies, taking into account all variables that influence the procedure related FLR. Furthermore, some of the above mentioned studies were performed a while ago at a time when ultrasound systems were less advanced and techniques and training in invasive procedures less standardized. A recent meta-analysis showed that accurate estimates of procedure-related risks following invasive procedures in the current clinical settings are lacking.55 Many experts believe that procedure related risks need reevaluation.56 Our
national guideline published in 2000 quotes a procedure related risks of 0.5% for CVS and 0.3% for AP, and these numbers are based on an Cochrane article from 1998, which is withdrawn, and an article based on a statistical model from 1991.57,58 Recent numbers for
the Netherlands are lacking.54 These numbers are important in order to prevent
discrep-ancies in information given to patients among different centers.
4. COUNSELING OF PARENTS AFTER AN ENLARGED NT
When after an increased nuchal translucency, the karyotype appears to be normal this cannot be regarded as a complete reassurance, as far as the final outcome of the pregnan-cy is concerned. This is especially the case in fetuses where the NT is severely increased. At present, after exclusion of chromosomal aberrations, the most challenging part of managing pregnancies with an increased NT is to establish an adequate diagnostic work-up and provide parents with realistic and correct information about outcome, especially long term neurological outcome.59-69
Our study group has investigated at length the associations between an enlarged NT and poor pregnancy outcome with the aim of correctly informing women on the associa-tions and on the predictors of poor or favorable outcome, given an enlarged NT (like sex-related-differences, impact of the size of the enlarged NT, other anomalies present be-sides the enlarged NT, and the possibility of an underlying genetic syndrome).9,11,23,59,70-86
There is a long and still growing list of genetic syndromes presenting with increased NT.60,72 Among the genetic syndromes the most frequently reported in combination with
an increased NT is Noonan syndrome (NS), with an incidence ranging from 2-6%. 65,69,87
NS is an autosomal dominant disorder caused in approximately 50% of the cases by a
missense mutation in the PTPN11 gene on chromosome 12.88 Mutations in the SOS1-,
RAF1-, KRAS-, BRAF-, MAP2K1/2-, NRAS- and SHOC2-genes account for a smaller percent-age of NS cases.89 In some clinically diagnosed NS cases the genetic background is still
unknown. Clinical diagnosis of Noonan syndrome is often challenging because of the great variability in clinical characteristics.90,91 The main facial characteristics are
hyper-telorism, downslanting palpebral fissures, epicanthic fold, ptosis and low set posteriorly angulated ears. The most common cardiovascular defects are pulmonary valve stenosis and hypertrophic cardiomyopathy. Other phenotypic characteristics are short stature, broad or webbed neck and chest deformity. Associated pathologies are haematological disorders (bleeding diathesis, juvenile myelomonocytic leukemia), lymphatic vessel dys-plasias, deafness and cryptorchidism. Affected individuals show a wide range in level of intelligence, with mental retardation being present in 15-35%, usually in the mild range and mainly consisting of specific visual-constructional problems and verbal perfor-mance discrepancy.91,92
The use of 3D rendering of the fetal face in case of (subtle) anomalies after an increased NT and normal karyotype could be a valuable tool in the prenatal detection of fetuses with NS, since the facial characteristics may be even more pronounced prenatally than postnatally.
A protocol for the management of pregnancies complicated by an increased NT to aid doctors in the prenatal follow-up of a fetus with an enlarged NT and a normal karyotype, especially to increase the prenatal detection rate of Noonan syndrome the most fre-quently encountered genetic syndrome, is still lacking.
5. FACIAL MARKERS IN THE FIRST TRIMESTER AND THEIR RELATIONSHIP WITH ANEUPLOIDIES AND OTHER FORMS OF ABNORMAL DEVELOPMENT
Assessment of the fetal face in the second trimester of pregnancy has become an impor-tant part of fetal evaluation, not only for the detection of facial anomalies but also in the setting of screening for trisomies, especially trisomy 21. Established second trimester profile markers for trisomies are the nasal bone length (NBL), the prenasal thickness (PNT), the ratio between the NBL and PNT and more recently the prefrontal space ratio (PFSR).22,93-95 Other second trimester profile parameters, e.g. the profile line (FP line) and
maxilla-nasion-mandible angle (MNM-angle), have been studied as markers for facial anomalies including profile alterations in case of aneuploidies.96-99 These are proven
reproducible markers for the diagnosis of retrognathia, maxillary alveolar ridge inter-ruption, sloping forehead, frontal bossing and flat profile. Reference values for most of these markers are available for the second trimester, however it has not yet been tried to see whether these markers can be measured in the first trimester and more importantly what their clinical significance would be.
The frontomaxillary facial angle (FMF-angle) and the NBL have been introduced in the first trimester to improve screening algorithms for trisomies and to improve detection rates and decrease false positive rates.16,17,100,101 Measurement of the PNT, PNT/ NBL ratio,
MNM-angle, FP line and PFSR in the first trimester could possibly further improve the detection of trisomies and/or facial abnormalities early in pregnancy.
Despite the rapid availability of cell free fetal DNA (cffDNA) as screening test for tri-somies, the CT is still the standard of care in the majority of countries. Further improve-ment of detection of trisomies is still valuable in case cffDNA is not performed or when it is performed as second tier test and to enhance the first trimester detection of struc-tural anomalies which are not trisomy related.
6. ANEUPLOIDIES AND FACIAL MARKERS IN THE SECOND TRIMESTER
Specific facial profile features of Down syndrome fetuses have been investigated and used as second and third trimester markers.22,94-99,102-105 The nasal bone length (NBL) was
the first to be extensively investigated, followed by the prenasal thickness (PT). Recent studies have shown that the ratio between these two markers (PT-NBL ratio) and the pre-frontal space ratio (PFSR) yields an even better detection rate.94,105 Furthermore, we have
previously investigated the maxilla-nasion-mandible (MNM) angle and fetal profile (FP) line in both euploid and pathological cases.97-99,106
Several studies have compared 2D and 3D US imaging during gestation and suggested 3D to be superior by allowing a better identification of anatomical landmarks, a higher ac-curacy and reproducibility in measurements of structures in the fetal face and profile, in-cluding the NBL. In a previous study, it was shown that 2D images judged to be midsagittal in fact are not and need 3D multiplanar correction of in average 11.9 (Y-axis) - 4.3 (Z-axis) degrees to become truly midsagittal.102 Clear landmarks to identify the exact midsagittal
plane are missing when only 2D imaging is used, making it difficult to be absolutely sure to be in the exact midsagittal plane.102 However, it is not clear whether addition of 3D
im-aging in a clinical setting 3D improves the detection rate when compared to 2D.
Aims of thesis
This thesis was designed to fill some of the gaps in knowledge that counselors, sonogra-phers and clinicians encounter in their daily practice when dealing with prenatal screen-ing and diagnosis. In view of the above mentioned clinical problems, we summarize the research questions as follows:
•
Why has the introduction of a national policy of first trimester prenatal screening for chromosomal anomalies been so poorly utilized by pregnant women and their part-ners and what are the factors affecting the uptake of the CT in the Netherlands?•
One of the factors mentioned by women declining the CT is that the NT measurementis not accurate and this influences the reliability of the risk assessment. Quality con-trols have indicated that some sonographers tend to underestimate the NT-measure-ments. In this respect the introduction of a technical tool aimed at standardizing the way the NT is measured may reduce such a bias. The following question was therefore: can the NT-measurement be improved by a semi-automated measurement?
•
One of the major determinants of a negative attitude towards the CT in the Nether-lands is the fear, in case on an increased risk, of having to undergo an invasive proce-dure that may lead to an iatrogenic abortion. We felt the need to redefine the actual risk of invasive procedures in a Dutch population since recent studies on this subject are in fact still missing. The investigated issues were: what is the total fetal loss rate and procedure-related risk for CVS and AP in the Dutch setting, and which maternal-, operator-, and procedure-related risk factors can be identified?•
At present the most challenging part of managing pregnancies with an increased NT, after exclusion of chromosomal aberrations, is to establish an adequate diagnostic work-up and provide parents with realistic and correct information about outcome,es-pecially long term neurological outcome in absence of structural anomalies. Therefore the study aim was: what are various aspects that should be investigated in the setting of an increased NT?
•
As Noonan syndrome is the most frequently observed genetic syndrome in fetuseswith an enlarged NT and normal karyotype, and, considering the diagnosis of this con-dition can be challenging: which ultrasound characteristics can guide us in the prena-tal diagnosis of Noonan syndrome?
•
Ultrasound measurement of facial markers has an increasingly important role in sec-ond trimester risk assessment and in the work-up of other facial anomalies, such as micrognathia. We wanted to investigate if these measurements can also be performed reliably in the first trimester of pregnancy. Therefore the next issue we have investi-gated was: can the PNT/NBL-ratio, MNM angle, FP line and PFSR already be measured in the first trimester of pregnancy? Are these measurements also useful markers of an abnormal development when measured in abnormal fetuses in the first trimester of pregnancy?•
The last question we wanted to answer was whether in the application of these facial markers at second trimester of pregnancy, 3D technique has an additional value with respect to the standard use of 2D technique. The question was therefore: is use of 3D technique superior to 2D technique when measuring the NB, PNT, FP line, MNM-an-gle, PNT/NB-ratio and PFSR, in Down syndrome screening?References
1. RIVM. Official Leaflet on Down Syndrome Screening.
2. Fleurke-Rozema J. H., Vogel T. A., Voskamp B. J., Pajkrt E., Van den Berg P. P., Beekhuis J. R., Bilardo C. M., Brouwer O. F., De Walle H. E., Snijders R. J. The impact of the intro-duction of the mid-trimester scan on preg-nancy outcome of open spina bifida in the Northern Netherlands. Ultrasound Obstet Gynecol 2013 Jun 25.
3. Nicolaides K. H., Azar G., Byrne D., Mansur C., Marks K. Fetal nuchal translucency: ultrasound screening for chromosomal defects in first trimester of pregnancy. BMJ 1992 Apr 4; 304(6831): 867-869.
4. Pandya P. P., Snijders R. J., Johnson S. P., De Lourdes Brizot M., Nicolaides K. H. Screen-ing for fetal trisomies by maternal age and fetal nuchal translucency thickness at 10 to 14 weeks of gestation. Br J Obstet Gynaecol 1995 Dec; 102(12): 957-962.
5. Snijders R. J., Noble P., Sebire N., Souka A.,
Nicolaides K. H. UK multicentre project on assessment of risk of trisomy 21 by maternal age and fetal nuchal-translucency thickness at 10-14 weeks of gestation. Fetal Medicine Foundation First Trimester Screening Group. Lancet 1998 Aug 1; 352(9125): 343-346.
6. Kagan K. O., Etchegaray A., Zhou Y., Wright D., Nicolaides K. H. Prospective validation of first-trimester combined screening for tri-somy 21. Ultrasound Obstet Gynecol 2009 Jul; 34(1): 14-18.
7. Kagan K. O., Wright D., Baker A., Sahota D., Nicolaides K. H. Screening for trisomy 21 by maternal age, fetal nuchal translucency thickness, free beta-human chorionic go-nadotropin and pregnancy-associated plas-ma protein-A. Ultrasound Obstet Gynecol 2008 Jun; 31(6): 618-624.
8. Nicolaides K. H. Screening for fetal aneu-ploidies at 11 to 13 weeks. Prenat Diagn 2011 Jan; 31(1): 7-15.
9. Muller M. A., Bleker O. P., Bonsel G. J., Bi-lardo C. M. Women's opinions on the offer and use of nuchal translucency screening for Down syndrome. Prenat Diagn 2006 Feb; 26(2): 105-111.
10. Van den Berg M., Timmermans D. R., Klein-veld J. H., Garcia E., Van Vugt J. M., Van der Wal G. Accepting or declining the offer of prenatal screening for congenital defects: test uptake and women's reasons. Prenat Diagn 2005 Jan; 25(1): 84-90.
11. Pajkrt E., Bilardo C. M., Van Lith J. M., Mol B. W., Bleker O. P. Nuchal translucency mea-surement in normal fetuses. Obstet Gynecol 1995 Dec; 86(6): 994-997.
12. Souka A. P., Von Kaisenberg C. S., Hyett J. A., Sonek J. D., Nicolaides K. H. Increased nuchal translucency with normal karyotype. Am J Obstet Gynecol 2005 Apr; 192(4): 1005-1021.
13. Kagan K. O., Wright D., Etchegaray A., Zhou Y., Nicolaides K. H. Effect of deviation of nuchal translucency measurements on the performance of screening for trisomy 21. Ultrasound Obstet Gynecol 2009 Jun; 33(6): 657-664.
14. Schmidt P., Staboulidou I., Elsasser M., Vaske B., Hillemanns P., Scharf A. How imprecise may the measurement of fetal nuchal translucency be without worsening first-trimester screening? Fetal Diagn Ther 2008; 24(3): 291-295.
15. Bilardo C. M., Muller M. A., Zikulnig L., Schipper M., Hecher K. Ductus venosus studies in fetuses at high risk for chromo-somal or heart abnormalities: relationship with nuchal translucency measurement and fetal outcome. Ultrasound Obstet Gynecol 2001 Apr; 17(4): 288-294.
16. Cicero S., Curcio P., Papageorghiou A., Sonek J., Nicolaides K. Absence of nasal bone in fetuses with trisomy 21 at 11-14 weeks of gestation: an observational study. Lancet 2001 Nov 17; 358(9294): 1665-1667. 17. Cicero S., Bindra R., Rembouskos G.,
Trip-sanas C., Nicolaides K. H. Fetal nasal bone
length in chromosomally normal and ab-normal fetuses at 11-14 weeks of gestation. J Matern Fetal Neonatal Med 2002 Jun; 11(6): 400-402.
18. Cicero S., Longo D., Rembouskos G., Sacchi-ni C., Nicolaides K. H. Absent nasal bone at 11-14 weeks of gestation and chromosomal defects. Ultrasound Obstet Gynecol 2003 Jul; 22(1): 31-35.
19. Cicero S., Avgidou K., Rembouskos G., Ka-gan K. O., Nicolaides K. H. Nasal bone in first-trimester screening for trisomy 21. Am J Obstet Gynecol 2006 Jul; 195(1): 109-114. 20. Matias A., Gomes C., Flack N., Montenegro
N., Nicolaides K. H. Screening for chromo-somal abnormalities at 10-14 weeks: the role of ductus venosus blood flow. Ultrasound Obstet Gynecol 1998 Dec; 12(6): 380-384. 21. Orlandi F., Bilardo C. M., Campogrande M.,
Krantz D., Hallahan T., Rossi C., Viora E. Measurement of nasal bone length at 11-14 weeks of pregnancy and its potential role in Down syndrome risk assessment. Ultra-sound Obstet Gynecol 2003 Jul; 22(1): 36-39. 22. Sonek J. D., McKenna D., Webb D., Croom
C,. Nicolaides K. Nasal bone length through-out gestation: normal ranges based on 3537 fetal ultrasound measurements. Ultrasound Obstet Gynecol 2003 Feb; 21(2): 152-155. 23. Timmerman E., Oude Rengerink K., Pajkrt
E., Opmeer B. C., Van der Post J. A., Bilardo C. M. Ductus venosus pulsatility index mea-surement reduces the false-positive rate in first-trimester screening. Ultrasound Ob-stet Gynecol 2010 Dec; 36(6): 661-667. 24. Bakker M., Birnie E., Pajkrt E., Bilardo C. M.,
Snijders R. J. Low uptake of the combined test in the Netherlands — which factors con-tribute? Prenat Diagn 2012 Dec; 32(13): 1305-1312.
25. Fransen M. P., Wildschut H. I., Mackenbach J. P., Steegers E. A., Galjaard R. J., Essink-Bot M. L. Ethnic and socio-economic differences in uptake of prenatal diagnostic tests for Down's syndrome. Eur J Obstet Gynecol Reprod Biol 2010 Aug; 151(2): 158-162.
26. Seror V., Ville Y. Prenatal screening for Down syndrome: women's involvement in decision-making and their attitudes to screening. Prenat Diagn 2009 Feb; 29(2): 120-128.
27. Ekelund C. K., Petersen O. B., Skibsted L., Kjaergaard S., Vogel I., Tabor A., Danish Fetal Medicine Research Group. First-trimester screening for trisomy 21 in Denmark: impli-cations for detection and birth rates of tri-somy 18 and tritri-somy 13. Ultrasound Obstet Gynecol 2011 Aug; 38(2): 140-144.
28. Rowe R., Puddicombe D., Hockley C., Redshaw M. Offer and uptake of prenatal screening for Down syndrome in women from different social and ethnic back-grounds. Prenat Diagn 2008 Dec; 28(13): 1245-1250.
29. Shantha N., Granger K., Arora P., Polson D. Women's choice for Down's screening – a comparative experience in three district general hospitals. Eur J Obstet Gynecol Re-prod Biol 2009 Sep; 146(1): 61-64.
30. Bilardo C. M., Pajkrt E., De Graaf I., Mol B. W., Bleker O. P. Outcome of fetuses with enlarged nuchal translucency and normal karyotype. Ultrasound Obstet Gynecol 1998 Jun; 11(6): 401-406.
31. The Fetal Medicine Foundation, 2010. 32. Pandya P. P., Altman D. G., Brizot M. L.,
Pet-tersen H., Nicolaides K. H. Repeatability of measurement of fetal nuchal translucency thickness. Ultrasound Obstet Gynecol 1995 May; 5(5): 334-337.
33. Abele H., Hoopmann M., Wright D., Hoff-mann-Poell B., Huettelmaier M., Pintoffl K., Wallwiener D., Kagan K. O. Intra- and in-teroperator reliability of manual and semi-automated measurement of fetal nuchal translucency by sonographers with differ-ent levels of experience. Ultrasound Obstet Gynecol 2010 Oct; 36(4): 417-422.
34. Grange G., Althuser M., Fresson J., Bititi A., Miyamoto K., Tsatsaris V., Morel O. Semi-automated adjusted measurement of nuchal translucency: feasibility and reproducibility.
Ultrasound Obstet Gynecol 2011 Mar; 37(3): 335-340.
35. Kagan K. O., Abele H., Yazdi B., Boer B., Pintoffl K., Wright D., Hoopmann M. Intra-operator and interIntra-operator repeatability of manual and semi-automated measurement of increased fetal nuchal translucency ac-cording to the operator's experience. Prenat Diagn 2011 Dec; 31(13): 1229-1233.
36. Moratalla J., Pintoffl K., Minekawa R., Lach-mann R., Wright D., Nicolaides K. H. Semi-automated system for measurement of nuchal translucency thickness. Ultrasound Obstet Gynecol 2010 Oct; 36(4): 412-416. 37. Kagan K. O., Avgidou K., Molina F. S.,
Gajew-ska K., Nicolaides K. H. Relation between in-creased fetal nuchal translucency thickness and chromosomal defects. Obstet Gynecol 2006 Jan; 107(1): 6-10.
38. Akolekar R., Beta J., Picciarelli G., Ogilvie C., DA'Antonio F. Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic re-view and meta-analysis. Ultrasound Obstet Gynecol 2014 Jul 17.
39. Tabor A., Alfirevic Z. Update on procedure-related risks for prenatal diagnosis tech-niques. Fetal Diagn Ther 2010; 27(1): 1-7. 40. Tabor A., Vestergaard C. H., Lidegaard O.
Fe-tal loss rate after chorionic villus sampling and amniocentesis: an 11-year national registry study. Ultrasound Obstet Gynecol 2009 Jul; 34(1): 19-24.
41. Akolekar R., Bower S., Flack N., Bilardo C. M., Nicolaides KH. Prediction of miscar-riage and stillbirth at 11-13 weeks and the contribution of chorionic villus sampling. Prenat Diagn 2011 Jan; 31(1): 38-45. 42. Smidt-Jensen S., Permin M., Philip J.,
Lund-steen C., Zachary J. M., Fowler S. E., Gruning K. Randomised comparison of amniocen-tesis and transabdominal and transcervical chorionic villus sampling. Lancet 1992 Nov 21; 340(8830): 1237-1244.
43. Tabor A., Philip J., Madsen M., Bang J., Obel E. B., Norgaard-Pedersen B. Randomised
controlled trial of genetic amniocentesis in 4606 low-risk women. Lancet 1986 Jun 7; 1(8493): 1287-1293.
44. Multicentre randomised clinical trial of chorion villus sampling and amniocentesis. First report. Canadian Collaborative CVS-Amniocentesis Clinical Trial Group. Lancet 1989 Jan 7; 1(8628): 1-6.
45. Giorlandino C., Cignini P., Cini M., Brizzi C., Carcioppolo O., Milite V., Coco C., Gentili P., Mangiafico L., Mesoraca A., Bizzoco D., Gabrielli I., Mobili L. Antibiotic prophylaxis before second-trimester genetic amnio-centesis (APGA): a single-centre open ran-domised controlled trial. Prenat Diagn 2009 Jun; 29(6): 606-612.
46. Corrado F., Cannata M. L., La Galia T., Magliarditi M., Imbruglia L, D'anna R., Carlo Stella N. Pregnancy outcome follow-ing mid-trimester amniocentesis. J Obstet Gynaecol 2012 Feb; 32(2): 117-119.
47. Centini G., Rosignoli L., Kenanidis A., Scar-inci R, Petraglia F. A report of early (13+0 to 14+6 weeks) and mid-trimester amniocen-teses: 10 years' experience. J Matern Fetal Neonatal Med 2003 Aug; 14(2): 113-117. 48. Caughey A. B., Hopkins L. M., Norton M. E.
Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss. Obstet Gynecol 2006 Sep; 108(3 Pt 1): 612-616.
49. Eddleman K. A., Malone F. D., Sullivan L., Dukes K., Berkowitz R. L., Kharbutli Y., Por-ter T. F., Luthy D. A., Comstock C. H., Saade G. R., Klugman S., Dugoff L., Craigo S. D., Timor-Tritsch I. E., Carr S. R., Wolfe H. M., D'Alton M. E. Pregnancy loss rates after midtrimester amniocentesis. Obstet Gyne-col 2006 Nov; 108(5): 1067-1072.
50. Odibo A. O., Dicke J. M., Gray D. L., Oberle B., Stamilio D. M., Macones G. A., Crane J. P. Evaluating the rate and risk factors for fetal loss after chorionic villus sampling. Obstet Gynecol 2008 Oct; 112(4): 813-819.
51. Pitukkijronnakorn S., Promsonthi P., Pan-burana P., Udomsubpayakul U.,
Chittacha-roen A. Fetal loss associated with second trimester amniocentesis. Arch Gynecol Ob-stet 2011 Oct; 284(4): 793-797.
52. Towner D., Currier R. J., Lorey F. W., Cun-ningham G. C., Greve L. C. Miscarriage risk from amniocentesis performed for abnor-mal maternal serum screening. Am J Obstet Gynecol 2007 Jun;196(6): 608.e1-5; discus-sion 608.e5.
53. Lau K. T., Leung Y. T., Fung Y. T., Chan L. W., Sahota D. S., Leung N. T. Outcome of 1,355 consecutive transabdominal chorionic vil-lus samplings in 1,351 patients. Chin Med J (Engl) 2005 Oct 20; 118(20): 1675-1681. 54. Cohen-Overbeek T. E., Hop W. C., Den
Ouden M., Pijpers L., Jahoda M. G., Wladi-miroff J. W. Spontaneous abortion rate and advanced maternal age: consequences for prenatal diagnosis. Lancet 1990 Jul 7; 336(8706): 27-29.
55. Akolekar R., Beta J., Picciarelli G., Ogilvie C., D'Antonio F. Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic re-view and meta-analysis. Ultrasound Obstet Gynecol 2015 Jan; 45(1): 16-26.
56. Akolekar R., Beta J., Picciarelli G., Ogilvie C., D'Antonio F. Reply. Ultrasound Obstet Gy-necol 2015 Jun; 45(6): 755-757.
57. Alfirevic Z., Gosden C. M., Neilson J. P. WITHDRAWN: Chorion villus sampling versus amniocentesis for prenatal diagno-sis. Cochrane Database Syst Rev 1996 Apr 22; (1)(1): CD000055.
58. Heckerling P. S., Verp M. S. Amniocentesis or chorionic villus sampling for prenatal genetic testing: a decision analysis. J Clin Epidemiol 1991; 44(7): 657-670.
59. Bilardo C. M., Muller M. A., Pajkrt E., Clur S. A., Van Zalen M. M., Bijlsma E. K. Increased nuchal translucency thickness and normal karyotype: time for parental reassurance. Ultrasound Obstet Gynecol 2007 Jul; 30(1): 11-18.
60. Souka A. P., Krampl E., Bakalis S., Heath V., Nicolaides K. H. Outcome of pregnancy
in chromosomally normal fetuses with increased nuchal translucency in the first trimester. Ultrasound Obstet Gynecol 2001 Jul; 18(1): 9-17.
61. Saldanha F. A., Brizot M. de L., Moraes E. A., Lopes L. M., Zugaib M. Increased fetal nuchal translucency thickness and normal karyotype: prenatal and postnatal follow-up. Rev Assoc Med Bras 2009 Sep-Oct; 55(5): 575-580.
62. Senat M. V., De Keersmaecker B., Audibert F., Montcharmont G., Frydman R., Ville Y. Pregnancy outcome in fetuses with in-creased nuchal translucency and normal karyotype. Prenat Diagn 2002 May; 22(5): 345-349.
63. Adekunle O., Gopee A., el-Sayed M., Thilaga-nathan B. Increased first trimester nuchal translucency: pregnancy and infant out-comes after routine screening for Down's syndrome in an unselected antenatal popu-lation. Br J Radiol 1999 May; 72(857): 457-460.
64. Cheng C. C., Bahado-Singh R. O., Chen S. C., Tsai M. S. Pregnancy outcomes with in-creased nuchal translucency after routine Down syndrome screening. Int J Gynaecol Obstet 2004 Jan; 84(1): 5-9.
65. Hiippala A., Eronen M., Taipale P., Salonen R., Hiilesmaa V. Fetal nuchal translucency and normal chromosomes: a long-term follow-up study. Ultrasound Obstet Gynecol 2001 Jul; 18(1): 18-22.
66. Maymon R., Jauniaux E., Cohen O., Dreazen E., Weinraub Z., Herman A. Pregnancy out-come and infant follow-up of fetuses with abnormally increased first trimester nuchal translucency. Hum Reprod 2000 Sep; 15(9): 2023-2027.
67. Senat M. V., Bussieres L., Couderc S., Roume J., Rozenberg P., Bouyer J., Ville Y. Long-term outcome of children born after a first-trimester measurement of nuchal translu-cency at the 99th percentile or greater with normal karyotype: a prospective study. Am J Obstet Gynecol 2007 Jan; 196(1): 53.e1-53.e6.
68. Van Vugt J. M., Tinnemans B. W., Van Zalen-Sprock R. M. Outcome and early childhood follow-up of chromosomally normal fetuses with increased nuchal translucency at 10-14 weeks' gestation. Ultrasound Obstet Gyne-col 1998 Jun; 11(6): 407-409.
69. Brady A. F., Pandya P. P., Yuksel B, Gree-nough A., Patton M. A., Nicolaides K. H. Out-come of chromosomally normal livebirths with increased fetal nuchal translucency at 10-14 weeks' gestation. J Med Genet 1998 Mar; 35(3): 222-224.
70. Bilardo C. M. Increased nuchal translucency and normal karyotype: coping with uncer-tainty. Ultrasound Obstet Gynecol 2001 Feb; 17(2): 99-101.
71. Bilardo C. M., Muller M. A., Pajkrt E. Out-come of fetuses with increased nuchal translucency. Curr Opin Obstet Gynecol 2001 Apr; 13(2): 169-174.
72. Bilardo C. M., Timmerman E., Pajkrt E., Van Maarle M. Increased nuchal translucency in euploid fetuses – what should we be telling the parents? Prenat Diagn 2010 Feb; 30(2): 93-102.
73. Muller M. A., Bleker O. P., Bonsel G. J., Bi-lardo C. M. Nuchal translucency screening and anxiety levels in pregnancy and puerpe-rium. Ultrasound Obstet Gynecol 2006 Apr; 27(4): 357-361.
74. Muller M. A., Bleker O. P., Bonsel G. J., Bi-lardo C. M. Women's opinions on the offer and use of nuchal translucency screening for Down syndrome. Prenat Diagn 2006 Feb; 26(2): 105-111.
75. Muller M. A., Clur S. A., Timmerman E., Bilardo C. M. Nuchal translucency measure-ment and congenital heart defects: modest association in low-risk pregnancies. Prenat Diagn 2007 Feb; 27(2): 164-169.
76. Muller M. A., Pajkrt E., Bleker O. P., Bonsel G. J., Bilardo C. M. Disappearance of en-larged nuchal translucency before 14 weeks' gestation: relationship with chromosomal abnormalities and pregnancy outcome. Ultrasound Obstet Gynecol 2004 Aug; 24(2):
169-174.
77. Muller M. A., Pajkrt E., Bilardo C. M. Ultra-sound screening for Down's syndrome early in pregnancy: nuchal translucency thick-ness. Ned Tijdschr Geneeskd 2002 Apr 27; 146(17): 793-798.
78. Pajkrt E., Bilardo C. M., Van Lith J. M., Mol B. W., Hansson K., Van Prooijen Knegt A. C., Bleker O. P. Ultrasound screening for fetal trisomies at 10-14 weeks' gestation. Early Hum Dev 1996 Dec 30; 47 Suppl: S35-6. 79. Pajkrt E., De Graaf I. M., Mol B. W., Van Lith
J. M., Bleker O. P., Bilardo C. M. Weekly nu-chal translucency measurements in normal fetuses. Obstet Gynecol 1998 Feb; 91(2): 208-211.
80. Pajkrt E., Mol B. W., Bleker O. P., Bilardo C. M. Pregnancy outcome and nuchal trans-lucency measurements in fetuses with a normal karyotype. Prenat Diagn 1999 Dec; 19(12): 1104-1108.
81. Pajkrt E., Mol B. W., Boer K., Drogtrop A. P., Bossuyt P. M., Bilardo C. M. Intra- and inter-operator repeatability of the nuchal trans-lucency measurement. Ultrasound Obstet Gynecol 2000 Apr; 15(4): 297-301.
82. Pajkrt E., Mol B. W., Van Lith J. M., Bleker O. P., Bilardo C. M. Screening for Down's syndrome by fetal nuchal translucency measurement in a high-risk population. Ultrasound Obstet Gynecol 1998 Sep; 12(3): 156-162.
83. Pajkrt E., Van Lith J. M., Mol B. W., Bleker O. P., Bilardo C. M. Screening for Down's syndrome by fetal nuchal translucency mea-surement in a general obstetric population. Ultrasound Obstet Gynecol 1998 Sep; 12(3): 163-169.
84. Timmerman E., Clur S. A., Pajkrt E., Bilardo C. M. First-trimester measurement of the ductus venosus pulsatility index and the prediction of congenital heart defects. Ul-trasound Obstet Gynecol 2010 Dec; 36(6): 668-675.
85. Timmerman E., Pajkrt E., Bilardo C. M. Male gender as a favorable prognostic factor in
pregnancies with enlarged nuchal translu-cency. Ultrasound Obstet Gynecol 2009 Oct; 34(4): 373-378.
86. Timmerman E., Pajkrt E., Maas S. M., Bilardo C. M. Enlarged nuchal translucency in chro-mosomally normal fetuses: strong associa-tion with orofacial clefts. Ultrasound Obstet Gynecol 2010 Oct; 36(4): 427-432.
87. Souka A. P., Snijders R. J., Novakov A., Soares W., Nicolaides K. H. Defects and syndromes in chromosomally normal fetuses with increased nuchal translucency thickness at 10-14 weeks of gestation. Ultrasound Obstet Gynecol 1998 Jun; 11(6): 391-400.
88. Tartaglia M., Mehler E. L., Goldberg R., Zampino G., Brunner H. G., Kremer H., Van der Burgt I., Crosby A. H., Ion A., Jeffery S., Kalidas K., Patton M. A., Kucherlapati R. S., Gelb B. D. Mutations in PTPN11, encoding the protein tyrosine phosphatase SHP-2, cause Noonan syndrome. Nat Genet 2001 Dec; 29(4): 465-468.
89. Jorge A. A., Malaquias A. C., Arnhold I. J., Mendonca B. B. Noonan syndrome and re-lated disorders: a review of clinical features and mutations in genes of the RAS/MAPK pathway. Horm Res 2009; 71(4): 185-193. 90. Noonan J. A. Noonan syndrome. An update
and review for the primary pediatrician. Clin Pediatr (Phila) 1994 Sep; 33(9): 548-555. 91. Allanson J. E., Roberts A. E. Noonan
Syn-drome. In: Pagon R. A., Adam M. P., Bird T. D., Dolan C. R., Fong C. T., Smith R. J. H., et al, editors. GeneReviews(R) Seattle (WA): University of Washington, Seattle; 1993. 92. Van der Burgt I., Thoonen G., Roosenboom
N., Assman-Hulsmans C., Gabreels F., Ot-ten B., Brunner H. G. Patterns of cognitive functioning in school-aged children with Noonan syndrome associated with variabil-ity in phenotypic expression. J Pediatr 1999 Dec; 135(6): 707-713.
93. Yazdi B., Riefler P., Fischmuller K., Sonek J., Hoopmann M., Kagan K. O. The frontal space measurement in euploid and aneu-ploid pregnancies at 11-13 weeks' gestation.
Prenat Diagn 2013 Dec; 33(12): 1124-1130. 94. De Jong-Pleij E. A., Vos F. I., Ribbert L. S.,
Pistorius L. R., Tromp E., Bilardo C. M. Pre-nasal thickness-to-Pre-nasal bone length ratio: a strong and simple second- and third-trimester marker for trisomy 21. Ultrasound Obstet Gynecol 2012 Feb; 39(2): 185-190. 95. Persico N., Borenstein M., Molina F.,
Azu-mendi G., Nicolaides K. H. Prenasal thick-ness in trisomy-21 fetuses at 16-24 weeks of gestation. Ultrasound Obstet Gynecol 2008 Nov; 32(6): 751-754.
96. Sonek J., Molina F., Hiett A. K., Glover M., McKenna D., Nicolaides K H. Prefrontal space ratio: comparison between trisomy 21 and euploid fetuses in the second trimester. Ultrasound Obstet Gynecol 2012 Sep; 40(3): 293-296.
97. De Jong-Pleij E. A., Ribbert L. S., Manten G. T., Tromp E, Bilardo C. M. Maxilla-nasion-mandible angle: a new method to assess profile anomalies in pregnancy. Ultrasound Obstet Gynecol 2011 May; 37(5): 562-569. 98. De Jong-Pleij E. A., Pistorius L. R., Ribbert L.
S., Breugem C. C., Bakker M., Tromp E., Bi-lardo C. M. Premaxillary protrusion assess-ment by the maxilla-nasion-mandible angle in fetuses with facial clefts. Prenat Diagn 2013 Apr; 33(4): 354-359.
99. De Jong-Pleij E. A., Ribbert L. S., Pistorius L. R., Tromp E., Bilardo C. M. The fetal profile line: a proposal for a sonographic refer-ence line to classify forehead and mandible anomalies in the second and third trimes-ter. Prenat Diagn 2012 Aug; 32(8): 797-802. 100. Borenstein M., Persico N., Kaihura C., Sonek
J., Nicolaides K. H. Frontomaxillary facial angle in chromosomally normal fetuses at
11+0 to 13+6 weeks. Ultrasound Obstet Gy-necol 2007 Oct; 30(5): 737-741.
101. Plasencia W., Dagklis T., Sotiriadis A., Boren-stein M., Nicolaides K. H. Frontomaxillary facial angle at 11+0 to 13+6 weeks' gestation-reproducibility of measurements. Ultra-sound Obstet Gynecol 2007 Jan; 29(1): 18-21. 102. De Jong-Pleij E. A., Ribbert L. S., Tromp E., Bi-lardo C. M. Three-dimensional multiplanar ultrasound is a valuable tool in the study of the fetal profile in the second trimester of pregnancy. Ultrasound Obstet Gynecol 2010 Feb; 35(2): 195-200.
103. Maymon R., Levinsohn-Tavor O., Cuckle H., Tovbin Y., Dreazen E., Wiener Y., Herman A. Second trimester ultrasound prenasal thick-ness combined with nasal bone length: a new method of Down syndrome screening. Prenat Diagn 2005 Oct; 25(10): 906-911. 104. Vos F. I., De Jong-Pleij E. A., Ribbert L. S.,
Tromp E., Bilardo C. M. Three-dimensional ultrasound imaging and measurement of nasal bone length, prenasal thickness and frontomaxillary facial angle in normal second- and third-trimester fetuses. Ultra-sound Obstet Gynecol 2012 Jun; 39(6): 636-641.
105. Yazdi B., Sonek J., Oettling C., Hoopmann M., Abele H., Schaelike M., Kagan K. O. Pre-frontal space ratio in second- and third-tri-mester screening for trisomy 21. Ultrasound Obstet Gynecol 2013 Mar; 41(3): 262-266. 106. Vos F. I., De Jong-Pleij E. A., Bakker M.,
Tromp E., Kagan K. O., Bilardo C. M. Fetal facial profile markers of Down syndrome in the second and third trimesters of pregnan-cy. Ultrasound Obstet Gynecol 2015 Aug; 46(2): 168-173.
2
Low uptake of the combined
test in the Netherlands –
which factors contribute?
M. Bakker 1
E. Birnie 1,4
E. Pajkrt 2
C. M. Bilardo 1
R. J. M. Snijders 3 1 Department of Obstetrics and Gynecology, Fetal Medicine Unit,
University Medical Centre, Groningen, the Netherlands.
2 Department of Obstetrics and Gynecology, Fetal Medicine Unit,
Academic Medical Centre, Amsterdam, the Netherlands.
3 Prenatal Screening Foundation Northeast Netherlands, University
Medical Centre, Groningen, the Netherlands.
4 Department of Genetics, University Medical Centre Groningen,
University of Groningen, Groningen, the Netherlands. Published in Prenatal Diagnosis 2012; 32, 1305-1312.
Low uptake of the combined test in the Netherlands
– which factors contribute?
M. Bakker1, E. Birnie1,4, E. Pajkrt2, C. M. Bilardo1 and R. J. M. Snijders3
1 Department of Obstetrics and Gynecology, Fetal Medicine Unit, University
Medical Centre, Groningen, the Netherlands.
2 Department of Obstetrics and Gynecology, Fetal Medicine Unit, Academic
Medical Centre, Amsterdam, the Netherlands.
3 Prenatal Screening Foundation Northeast Netherlands, University Medical
Centre, Groningen, the Netherlands.
4 Department of Genetics, University Medical Centre Groningen, University
of Groningen, Groningen, the Netherlands.
Objective:
Objective The aim of this study was to evaluate which of the following fac-tors affect the uptake of the combined test (CT) in the Netherlands: women’s socio-demographic background, attitude towards Down syndrome, attitude to-wards termination of pregnancy, coun-seling process, reimbursement policy, and knowledge on the aim of the CT. Methods:
Cross-sectional survey in the Northwest (NW) and the Northeast (NE) region of the Netherlands.
Results:
Analyses were based on 820 question-naires (73% response rate). Women from the NW region opted more often for the CT than women from the NE
region (52.1% and 16.5%, respectively,
p < 0.001). Women of 36 years and older
opted more often for the CT than young-er women (59.4% and 28.2%, respec-tively, p < 0.001). Women’s socio-demo-graphic background and their attitude towards Down syndrome and termina-tion of pregnancy (TOP) had contributed independently on CT choice.
Conclusion:
The uptake of the CT in this study is low. The main reason for the low uptake is the relatively positive attitude towards Down syndrome and a negative attitude towards TOP. Moreover, the perception of maternal age as strong predictor of Down syndrome risk and the inequal-ity of access to care, due to the financial threshold for younger women, are likely to affect participation in screening.
Introduction
The aim of the combined test (CT) is to identify fetuses with an increased risk for Down syndrome, thus offering parents the possibility to opt for invasive prenatal diagnosis. In case of an affected pregnancy, parents can opt for termination of pregnancy (TOP) or pre-pare themselves for the birth of a child with Down syndrome.
the aim to ask all pregnant women if they want to be informed about prenatal screening. If a woman wants to receive information, she is counseled by her healthcare profession-al, and on the basis of the information provided, she decides whether or not she wants to opt for screening. The Dutch Department of Health has introduced an age-related system for reimbursement of the CT; women aged 36 years and older have free access to the test, whereas younger women have to pay approximately 150 euros. If women of 36 years and older decline screening, they can still opt for prenatal diagnosis based on their age. Before 2007, the CT was offered in the Netherlands in research settings with uptake rates ranging from 53% to 86%.1,2 An important incentive for the present study was the
observation that since the start of the national screening program the uptake of the CT is low and lower than in the past, with pronounced regional differences.3,1,2 The aim of
this study was to evaluate which of the following factors affects the uptake of the CT in the Netherlands: women’s sociodemographic background, attitude towards Down syn-drome, attitude towards termination of pregnancy, counseling process, reimbursement policy, and knowledge on the aim of the CT.
Methods
DESIGN
Between March and April 2010, a cross-sectional survey was conducted at 13 ultrasound clinics in the Northwest (NW) and Northeast (NE) of the Netherlands to investigate the uptake of the CT. All pregnant women who attended the ultrasound center received an information letter and a questionnaire about the CT. The questionnaires were distrib-uted at the time of the 20-week anomaly scan to ensure that knowledge on the outcome of prenatal diagnosis would not bias women’s opinions on the CT in retrospect.
STUDY INSTRUMENT
The questionnaire used in the present study was based on a questionnaire developed in France by Seror et al.,4 addressing women’s attitudes and decisions on screening for
Down syndrome.
Our questionnaire included four sections with a total of 53 questions (see supporting information). The first section (six questions) contained questions regarding the dating scan in this pregnancy. The second section (23 questions) addressed the counseling and reasons for accepting or declining the CT. The third section (eight questions) assessed whether or not women opted for prenatal diagnosis. The final section contained ques-tions about women’s socio-demographic characteristics, attitude towards termination of pregnancy and costs of the first trimester scan. The following demographic variables were included as follows: age, parity, educational level, income status, region, and ethnicity.
STATISTICAL ANALYSIS
To compare differences in categorical variables between women who opted for the CT and those who declined, the X2 test (or Fisher’s Exact Test, if appropriate) was used. To
compare differences in continuous variables between these groups, the student’s t-test was used. Comparison by age was performed because only women aged 36 years and older receive reimbursement for the CT. Comparison by region was performed because differences between regions may reflect differences in determinants or uptake.
Associations between single co-variables and women’s decision to accept or decline the CT were assessed by univariate binary logistic regression and expressed in odds ra-tios (ORs, 95% confidence intervals). Next, multiple binary logistic regression analysis with stepwise backward conditional inclusion of variables was performed to evaluate the adjusted impact of co-variables. Correlations and stratified tables were used to check for confounding and interaction (income education). Multiple logistic regressions were redone accordingly, taking confounding and interaction into account.
To study the relative impact of co-variables on women’s decision, we distinguished six blocks of determinants: patient characteristics, women’s opinions and attitudes, care characteristics, decision making and women’s knowledge, reimbursement policy, and region. The relative impact of each block was evaluated by adding blocks of variables suc-cessively to the multiple binary logistic regression, and the change in 2 log likelihood
Table 1 — Socio-demographic characteristics of women opting for or declining the combined test (CT)
¬ ¬ ¬ ¬ ¬ ¬ ¬ CT ¬ ¬ ¬ ¬ ¬ ¬ ¬ Variables No N(%) Yes N(%) p Age: ≤29 307 (55.1) 86 (32.7) 30-35 209 (37.5) 117 (44.5) ≥36 41 (7.4) 60 (22.8) <0.001 Education: Low 57 (10.4) 25 (9.6) Middle 250 (45.5) 100 (38.3) High 243 (44.2) 136 (52.1) 0.101 Income: <1500 euros 43 (8.1) 18 (7.2) 1500-3500 euros 375 (71.0) 129 (51.8) >3500 euros 110 (20.8) 102 (41.0) <0.001 Parity: Primiparous 271 (48.7) 119 (45.2) Multiparous 286 (51.3) 144 (54.8) 0.370 Etnicity: Caucasian 385 (83.9) 199 (84.0) Non-Caucasian 74 (16.1) 38 (16.0) >0.99 Religion: Important 163 (29.7) 44 (16.8) Not important 386 (70.3) 218 (83.2) <0.001 Region: Northeast 385 (69.1) 76 (28.9) Northwest 172 (30.9) 187 (71.1) <0.001
Table 2 — Information provided on the combined test (CT)
¬ ¬ ¬ ¬ ¬ ¬ ¬ CT ¬ ¬ ¬ ¬ ¬ ¬ ¬
Information provided No N(%) Yes N(%) p Who discussed the possibility of the CT with you
General physician 14 (2.6) 2 (0.3) Midwife 444 (83.9) 192 (73.3) Gynecologist 48 (9.1) 40 (15.3) Sonographer 8 (1.5) 11 (4.2)
Searched autonomously for information 15 (2.8) 17 (6.5) <0.001
Was the amount of information enough
Too much information 5 (0.9) 1 (0.4) Enough information 515 (95.9) 253 (96.2)
Too little information 17 (3.2) 9 (3.4) 0.756
Did you get written information in addition to oral information
Yes, a leaflet on Down syndrome screening 430 (80.7) 230 (87.5) Yes, information on the Decision Aid on the internet 16 (3.0) 9 (3.4)
No, I did not receive any written information 87 (16.3) 24 (9.1) <0.022
Would you prefer to receive the written information before or after counseling
Before 213 (40.2) 159 (60.5) After 216 (40.8) 33 (12.5)
I do not know 101 (19.1) 71 (27) <0.001
was evaluated and the proportion of cases correctly predicted.
Statistical significance was defined as p < 0.05 (two-sided). All statistical analyses were conducted using SPSS 17.0.0.
Results
A total of 837 (73.0%) of 1140 women returned the questionnaire. Analyses were based on 820 women; 17 questionnaires were excluded from analysis because women had already opted for prenatal diagnosis and were aware whether or not their child was affected at the time the questionnaire was filled out; nine of these women had declined, and eight women had opted for the CT. Table 1 shows that 263 (32.1%) participants opted for the CT. Acceptors were on average older than decliners: 31.4 and 29.0 years, respectively (p < 0.001). There were no significant age differences between the NW and NE regions. Most women were counseled by their midwife (N=636, 80.4%), and the first visit took usually place at 7 to 8 weeks of gestation (N=356, 43.8%). Besides oral information, 660 (82.9%) women received the leaflet on Down syndrome screening developed by the Dutch National Screening Board, and 25 (3.1%) women used the Decision Aid on the internet. A subgroup of 111 (13.9%) women reported not to have received any written information. Most women who opted for the CT preferred to receive the information before counseling (N=159, 60.5%) in contrast to 40.2% of women who declined (N=213) (p < 0.001). More women who declined the CT indicated that they did not receive any written information (N=87, 16.3%) than women who opted for the CT (N=24, 9.1%)
(p < 0.022) (Table 2).
The vast majority of women reported to have made the decision on CT autonomously (N=648, 81.5%) and before the counseling had taken place (N=475, 59.9%). Women who opted for the CT more frequently reported having received a positive advice from the healthcare professional (N=33, 12.8%) than decliners (N=13, 2.5%) (p < 0.001). Similarly, women of 36 years and older were more frequently advised to opt for the CT (N=14, 14.6%) than younger women (N=31, 4.7%) (p < 0.002). The majority of women reported that it had been easy to decide whether or not to opt for prenatal screening (N=601, 75.4%). More acceptors found the decision easy (N=212, 81.2%) than decliners (N=389,
Table 3 — Reasons to opt for the combined test (CT) (multiple answers possible per participant)
Reasons to opt for the CT
Total acceptors = 263 Total answersN=425 <36 yearsanswers N(%) ≥36 yearsanswers N(%) p NE regionN(%) NW regionN(%) p
I want to know if there is an increased risk on Down syndrome
223 (84.8) 179 (88.2) 44 (73.3) 0.008 59 (77.6) 164 (87.7) 0.057
I will opt for all tests offered 26 (9.9) 25 (12.3) 1 (1.7) 0.013 6 (7.9) 20 (10.7) 0.649 I am of older age and I rather
opt for the CT than for an invasive procedure
61 (23.2) 16 (7.9) 45 (75.0) <0.001 25 (32.9) 36 (19.3) 0.024
I had the CT in previous
pregnancy 79 (30.0) 64 (31.5) 15 (25.0) 0.423 19 (25.0) 60 (32.1) 0.300 My midwife/family/friends
advised me to do the CT 14 (5.3) 7 (3.4) 7 (11.7) 0.021 2 (2.6) 12 (6.4) 0.363 Other reasons 22 (8.4) 18 (8.9) 4 (6.7) 0.792 5 (6.6) 17 (9.1) 0.627
NW = Northwest. NE = Northeast.
Table 4 — Reasons to decline the combined test (CT) (multiple answers possible per participant)
Reasons to decline the CT
Total decliners = 557 Total answersN=1101 <36 yearsanswers N(%) ≥36 yearsanswers N(%) p NE regionN(%) NW regionN(%) p
I am young and therefore
the test is unnecessary 191 (34.3) 189 (36.6) 2 (4.9) <0.001 134 (34.8) 57 (33.1) 0.772 I want to minimize testing
during this pregnancy 30 (5.4) 26 (5.0) 4 (9.8) 0.266 19 (4.9) 11 (6.4) 0.543 I think my risk on Down
syndrome is low 138 (24.8) 133 (25.8) 5 (12.2) 0.060 100 (26.0) 38 (22.1) 0.341 I do not want to make a
decision on TOP 123 (22.1) 111 (21.5) 12 (29.3) 0.245 80 (20.8) 43 (25.0) 0.271 Down syndrome is for me
no reason to terminate a pregnancy
321 (57.6) 292 (56.6) 29 (70.7) 0.100 236 (61.3) 85 (49.4) 0.009
The test does not give any
guarantees 16 (2.9) 14 (2.7) 2 (4.9) 0.332 11 (2.9) 5 (2.9) >0.99 I have the impression that
the test is not reliable 191 (34.3) 178 (34.5) 13 (31.7) 0.864 127 (33.0) 64 (37.2) 0.336 I found the test too expensive 37 (6.6) 37 (7.2) 0 (0) 0.099 20 (5.2) 17 (9.9) 0.044 Other reasons 54 (9.7) 51 (9.9) 3 (7.3) 0.786 31 (8.1) 23 (13.4) 0.062
72.6%) (p=0.007). Decliners reported more often that they were unaware a decision was being made (N=105, 19.6%) than ac-ceptors (N=28, 10.7%) (p=0.007). Women from the NE region were more frequently unaware a decision was being made (N=87, 19.5%) in comparison to women from the NW region (N=46, 13.1%) (p=0.040). The reasons to opt for the CT are shown in Table 3. The main reason to opt for CT was to obtain an individualized risk assess-ment on Down syndrome (N=223, 84.8%). Women of 36 years and older opted more often for the CT than younger women be-cause others advised them to opt for the CT (N=7, 11.7% vs. N=7, 3.4%; p=0.021). In the NE region, older women more often opted for the CT to avoid an invasive procedure (N=25, 32.9%) than women from the NW region (N=36, 19.3%; p=0.024).
The main reason to decline the CT was that women would not consider TOP in case of Down syndrome (N=321, 57.6%) (Table 4). Younger women declined the CT more often than women of 36 years and older because they considered their age-related risk to be low (N=189, 36.6% vs. N=2, 4.9%; p < 0.001). Women from the NE region declined the CT more often because Down syndrome would not be a reason to consider TOP (N=236, 61.3% vs. N=85, 49.4%; p=0.009) and women from the NW more often declined the CT because they found it too expensive (N=17, 9.9% vs. N=20, 5.2%; p=0.044).
Acceptors of the CT would consider TOP in case of Down syndrome more often than decliners (Table 5). A subgroup of 210 (39.2%) women would consider a TOP in case of severe physical anomaly. Women from the NE region would consider TOP in case of Down syndrome less often than women from the NW region (N=46, 10.3% vs. N=108, 30.6%; p < 0.001). There were no significant differences in attitude towards TOP between the two age-groups.
Table 5 — Attitude towards termination of pregnancy
Attitude towards TOP
Combined test p <36 years answers N(%) ≥36 years answers N(%) p NE region N(%) NW region N(%) p No N(%) Yes N(%)
Consider termination of pregnancy in case of Down syndrome
30 (5.6) 124 (47.3) 131 (18.7) 23 (23.2) 46 (10.3) 108 (30.6)
Consider termination of pregnancy in case of severe structural anomaly
210 (39.2) 74 (28.2) 247 (35.3) 37 (27.4) 173 (38.9) 111 (31.4)
I did not think termination of pregnancy was an option
172 (32.1) 52 (19.8) 201 (28.8) 23 (23.2) 133 (29.9) 91 (25.8)
I will always carry to term
124 (23.1) 12 (4.6) <0.001 120 (17.2) 16 (16.2) 0.572 93 (20.9) 43 (12.2) <0.001
TOP = termination of pregnancy. NW = Northwest. NE = Northeast.
Table 3 — Reasons to opt for the combined test (CT) (multiple answers possible per participant)
Reasons to opt for the CT
Total acceptors = 263 Total answersN=425 <36 yearsanswers N(%) ≥36 yearsanswers N(%) p NE regionN(%) NW regionN(%) p
I want to know if there is an increased risk on Down syndrome
223 (84.8) 179 (88.2) 44 (73.3) 0.008 59 (77.6) 164 (87.7) 0.057
I will opt for all tests offered 26 (9.9) 25 (12.3) 1 (1.7) 0.013 6 (7.9) 20 (10.7) 0.649 I am of older age and I rather
opt for the CT than for an invasive procedure
61 (23.2) 16 (7.9) 45 (75.0) <0.001 25 (32.9) 36 (19.3) 0.024
I had the CT in previous
pregnancy 79 (30.0) 64 (31.5) 15 (25.0) 0.423 19 (25.0) 60 (32.1) 0.300 My midwife/family/friends
advised me to do the CT 14 (5.3) 7 (3.4) 7 (11.7) 0.021 2 (2.6) 12 (6.4) 0.363 Other reasons 22 (8.4) 18 (8.9) 4 (6.7) 0.792 5 (6.6) 17 (9.1) 0.627
NW = Northwest. NE = Northeast.
Table 4 — Reasons to decline the combined test (CT) (multiple answers possible per participant)
Reasons to decline the CT
Total decliners = 557 Total answersN=1101 <36 yearsanswers N(%) ≥36 yearsanswers N(%) p NE regionN(%) NW regionN(%) p
I am young and therefore
the test is unnecessary 191 (34.3) 189 (36.6) 2 (4.9) <0.001 134 (34.8) 57 (33.1) 0.772 I want to minimize testing
during this pregnancy 30 (5.4) 26 (5.0) 4 (9.8) 0.266 19 (4.9) 11 (6.4) 0.543 I think my risk on Down
syndrome is low 138 (24.8) 133 (25.8) 5 (12.2) 0.060 100 (26.0) 38 (22.1) 0.341 I do not want to make a
decision on TOP 123 (22.1) 111 (21.5) 12 (29.3) 0.245 80 (20.8) 43 (25.0) 0.271 Down syndrome is for me
no reason to terminate a pregnancy
321 (57.6) 292 (56.6) 29 (70.7) 0.100 236 (61.3) 85 (49.4) 0.009
The test does not give any
guarantees 16 (2.9) 14 (2.7) 2 (4.9) 0.332 11 (2.9) 5 (2.9) >0.99 I have the impression that
the test is not reliable 191 (34.3) 178 (34.5) 13 (31.7) 0.864 127 (33.0) 64 (37.2) 0.336 I found the test too expensive 37 (6.6) 37 (7.2) 0 (0) 0.099 20 (5.2) 17 (9.9) 0.044 Other reasons 54 (9.7) 51 (9.9) 3 (7.3) 0.786 31 (8.1) 23 (13.4) 0.062
Table 6 — Univariate and multivariate analysis – which factors influence combined test (CT) choice
Univariate logistic regression Multiple logistic regression
Variables OR (95% CI) p OR (95% CI) p
BLOCK 1 – socio-demographics Age: ≤29 1 ¬ 1 ¬ 30-35 2.00 (1.44 – 2.78) <0.001 2.00 (1.17 – 3.35) 0.011 ≥36 5.22 (3.29 – 8.31) <0.001 5.61 (2.77 – 11.33) <0.001 Parity: Primiparous 1 ¬ Multiparous 1.15 (0.85 – 1.54) <0.362 Etnicity: Caucasian 1 ¬ Non-Caucasian 0.99 (0.65 – 1.52) 0.976 Education: Low 1 ¬ Middle 0.91 (0.54 – 1.54) 0.731 High 1.28 (0.76 – 2.14) 0.353 Income: <1500 1 ¬ 1 ¬ 1500-3500 0.82 (0.46 – 1.48) 0.511 1.52 (0.52 – 4.50) 0.447 >3500 2.2 (1.20 – 4.08) 0.011 2.56 (0.80 – 8.22) 0.114 Ever TOP: No 1 ¬ 1 ¬ Yes 3.25 (1.75 – 6.04) <0.001 1.81 (0.76 – 4.34) 0.183 BLOCK 2 – attitude Opinion TOP:
TOP in case of Down 1 ¬ 1 ¬ TOP in case of anomaly 0.09 (0.05 – 0.14) <0.001 0.14 (0.07 – 0.26) <0.001 Never thought about it 0.07 (0.04 – 0.12) <0.001 0.11 (0.06 – 0.22) <0.001 Always carry to term 0.02 (0.01 – 0.05) <0.001 0.04 (0.02 – 0.09) <0.001
Positive opinion on offer national screening:
No 1 ¬ I do not know 5.83 (0.64 – 52.90) 0.117 Yes 7.54 (0.99 – 57.43) 0.051 BLOCK 3 – counseling CT discussed by: Midwife 1 ¬ 1 ¬ Self 2.62 (1.28 – 5.40) 0.008 3.71 (1.07 – 12.84) 0.038 General physician 0.33 (0.07 – 1.50) 0.145 0.46 (0.04 – 5.83) 0.550 Gynecologist 1.93 (1.23 – 3.03) 0.004 1.18 (0.58 – 2.39) 0.653 Sonographer 3.20 (1.26 – 8.03) 0.014 6.47 (1.20 – 35.01) 0.030 CT information: Enough 1 ¬ Too much 0.41 (0.05 – 3.50) 0.413 Too little 1.08 (0.47 – 2.45) 0.858
Table 6 (continued)
Univariate logistic regression Multiple logistic regression
Variables OR (95% CI) p OR (95% CI) p Type of CT information:
No written information 1 ¬ 1 ¬ Official leaflet 1.94 (1.20 – 3.13) 0.007 3.12 (1.44 – 6.75) 0.004 Decision aid on internet 2.04 (0.80 – 5.19) 0.135 0.94 (0.19 – 4.65) 0.939
Timing of CT information:
Before counseling 1 ¬ 1 ¬
I do not know 0.44 (0.28 – 0.68) <0.001 0.42 (0.21 – 0.87) 0.019 After counseling 0.44 (0.31 – 0.62) <0.001 0.40 (0.24 – 0.67) <0.001
Advice from healthcare professional:
Informed choice 1 ¬ 1 ¬
Do not opt for CT 0.63 (0.20 – 0.1.93) 0.417 0.40 (0.09 – 1.77) 0.224 Opt for CT 5.58 (2.88 – 10.81) <0.001 14.97 (4.26 – 52.60) <0.001
Follow advice health care professional:
Decide without help 1 ¬ 1 ¬ Decide with help 0.88 (0.53 – 1.47) 0.624 0.53 (0.23 – 1.22) 0.141 Follow advice 1.96 (1.28 – 3.01) 0.002 1.72 (0.84 – 3.54) 0.136 BLOCK 4 – decision making
Decision difficulty:
Easy 1 ¬
Hard 0.92 (0.53 – 1.60) 0.759 Did not know a decision
was being made 0.49 (0.31 – 0.78) 0.002
Decision made:
Before counseling 1 ¬ 1
During counseling 0.78 (0.52 – 1.17) 0.226 1.43 (0.70 – 2.91) 0.323 After counseling 0.48 (0.33 – 0.72) <0.001 0.54 (0.30 – 0.95) 0.033 BLOCK 5 – costs and knowledge
Opinion on costs:
Alright to pay 1 ¬ 1 ¬
Only opt for CT in case
of reimbursement 0.26 (0.13 – 0.52) <0.001 0.29 (0.10 – 0.89) 0.030 Only opt for CT if cheaper 0.59 (0.35 – 0.99) 0.045 1.59 (0.75 – 3.35) 0.227
Knowledge on purpose of CT 1.28 (1.09 – 1.51) 0.003 BLOCK 6 – region
Region:
Northeast 1 ¬ 1 ¬
Northwest 5.51 (4.00 – 7.60) <0.001 4.86 (3.01 – 7.83) <0.001
Block 1: 2 log likelihood 739.009, correctly predicted 67.9%. Block 2: 2 log likelihood 618.411, correctly predicted 76.9%. Block 3: 2 log likelihood 547.756, correctly predicted 79.7%. Block 4: 2 log likelihood 542.302, correctly predicted 79.2%. Block 5: 2 log likelihood 534.612, correctly predicted 79.4%. Block 6: 2 log likelihood 489.050, correctly predicted 82.8%.
