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Risk selection and detection. A critical appraisal of the Dutch obstetric system
Bais, J.M.J.
Publication date
2004
Link to publication
Citation for published version (APA):
Bais, J. M. J. (2004). Risk selection and detection. A critical appraisal of the Dutch obstetric
system.
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Introductionn and outline of this thesis
INTRODUCTION N
1.1.. The Dutch risk selection system of obstetric care, general information
Thee Dutch system of obstetric care is based upon risk management: primary care, providedd by midwives and general practitioners for low-risk pregnancies, and second-aryy care, provided under the responsibility of obstetricians, for high-risk pregnancies. Thiss system is supported by the prevalent opinion among obstetric professionals and thee general public in the Netherlands that pregnancy, labour and childbed are essen-tiallyy physiologic events [1]. Moreover, specialist care during pregnancy, delivery or puerperiumm is remunerated only if medical reasons or obstetric pathology warrant suchh care.
Thee intervention rate during labour is increasing, but still low compared to other Europeann countries [2]. The caesarean section rate in 13 European countries in the periodd 1998-2001 ranged from 11.7 to 30.5%, the Dutch rate being by far the lowest (Tablee 1.1) [2].
Bothh primary care and secondary care agreed upon a guideline (Verloskundige In-dicatielijst)) [3] for risk assessment at the booking visit and for consultation or referral inn case of suspected or assessed pathology during pregnancy, delivery or puerperial period.. This guideline distinguishes three risk classes:
(1)) Continued low risk
Inn the Netherlands midwives (or general practitioners) perform prenatal, intrapar-tumm and postnatal care in low-risk women with uncomplicated obstetric and med-icall history, and uneventful pregnancy, delivery and puerperial period. Midwives aree qualified and licensed to provide independent care in low-risk women (primary care).. Low-risk women can choose between a home or hospital delivery, both under responsibilityy of the midwife.
(2)) Secondary high risk
Riskk factors/complications arise during pregnancy, labour or childbed, with ensu-ingg referral from primary to secondary care (obstetricians).
(3)) Initially high risk
Iff the medical or obstetric history indicates high risk, the woman receives second-aryy care. This care is provided by midwives, house officers or registrars working underr the supervision of obstetricians, or by obstetricians.
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'CC c 'E O.. >, C ww c w _ U S U I ) ) "'' E " ~ c c T33 ^ G U U -- U u _ -< B 3 Ü t t . t O O i i MM J Z v i e e CC c o 33 P —— 33 I i; u «22 e 55 E EE 1 >> 4§ « CC '-] o EE -o J2 33 U (,maryy caregivers. Of this exclusively primary care group the majority deliver at home: 30%% of all deliveries take place at home [4].
Registrationn is performed in the Dutch Perinatal Database, 'Landelijke Verlos-kundee Registratie' (LVR). The LVR contains two databases, the LVR1 for primary caree and the LVR2 for referred and exclusively secondary care.
Thesee databases are not perfect, as linking of both databases is complicated by privacyy legislation, while a lot of referred cases are registered both in LVR1 and LVR2,, and participation is not 100%. General practitioners do not participate ( < 2% off all deliveries), some midwifery practices do not participate, and every year techni-calitiess exclude the data of some practices (LVR1 and LVR2)
1.2.. Effectiveness of the system of risk selection
Thee effectiveness of the system theoretically should be established by comparing in aa random design the outcome of a large cohort with and without risk management, all otherr things equal. For obstetrical reasons this is impossible, restricting the methods too observational approaches.
Thee effectiveness can be more indirectly assessed by studying the three groups re-sultingg from the selection: exclusively primary care, secondary high risk after referral duringg pregnancy or labour and exclusively secondary care.
Withh perfect selection, the exclusively primary care group contains only healthy womenn with singleton term vertex infants of normal birth weight. The secondary high-riskk group, referred after obstetric pathology is established during pregnancy, containss women with obstetric complications as hypertension, intrauterine growth re-tardation,, gestational diabetes, abnormal presentation, preterm labour or postterm pregnancy,, or - in case of referral during labour - failure to progress or meconium-stainedd fluid. The exclusively secondary care group should contain women with a highh risk based on medical or obstetric history.
Adversee obstetric outcome like perinatal mortality and morbidity and the inci-dencee of obstetric interventions as caesarean section should be different in those three groups.. Perinatal morbidity can be defined as Apgar score below 7 at 5 min, low um-bilicall cord pH values, low birth weight, admission to the neonatal ward, neonatal sei-zures,, non-optimal neurological score etc.
Itt follows that perinatal morbidity and mortality should be the highest in the sec-ondaryy high-risk group, referred during pregnancy, followed by the initially high-risk groupp and then the group referred during labour. The exclusively primary care group shouldd have extremely low perinatal morbidity and mortality rates.
1.3.. Previous studies on effectiveness of the system of risk selection
Previouss studies on risk selection show a non-optimal selection in low- and
high-riskk cases. In a large cohort of fetal deaths in 1961 (JV=3724) in nearly 33% risk factors
placee in primary care [5]. The same phenomenon was described in the study of Smits [6]:: in hindsight 33% pregnancies were unjustly not selected as high risk. Moreover a considerablee amount of low-risk cases (22%) were present in the secondary care group. Thiss resulted in an equal distribution of perinatal mortality, small for gestational age andd preterm births in the group selected as low risk compared to the group selected as highh risk.
Inn the early 1980s two studies were published comparing umbilical cord pH values andd neurological optimality scores in home-delivered infants vs infants delivered in hospitall (primary and secondary care), and in primary care vs secondary care [7,8]. Thesee studies found better outcome measured by umbilical cord pH and neurological optimalityy scores for hospital-delivered infants compared to home-born infants, and infantss in the secondary care group compared to primary care. The authors concluded thatt the better results obtained by obstetrician-led care were due to continuous fetal heartt rate monitoring in opposite to discontinued heart rate monitoring performed byy midwives. These studies were criticised on methodological grounds; selection bias inn study groups, and non-optimal standardisation of blood sampling and storage [9,10]. .
1.3.1.1.3.1. The Wormerveer study
Inn 1989 the Wormerveer study was published, a long-term prospective cohort study,, which focused on the effectiveness of primary care performed by independent midwivess in a small suburb north of Amsterdam [11,12]. The study comprised a peri-odd of 14 years (1969-1983), with a complete follow-up of 7980 pregnancies, deliveries andd 8055 children. In this study the selection process in low and high risk was evalu-ated,, apart from perinatal morbidity and mortality. Perinatal mortality was defined as alll fetal and neonatal deaths within the first week of life, of fetuses and neonates with a birthh weight >500 g. Perinatal morbidity was defined as neonatal admission and sei-zuress within the first week of life. Follow-up of all infants was registered until at least 44 weeks, and neonatal mortality during a year.
Perinatall mortality was 11.1 per 1000, low compared to national figures at that timee (14.5 per 1000). Perinatal mortality rate was higher in the group of 1430 infants bornn under secondary care, and referred during pregnancy (51.7 per 1000) compared too the low-risk group not referred during pregnancy (2.3 per 1000). Of all 89 registered perinatall deaths, 15 (17%) occurred in the group of 6625 infants (82%) born to motherss selected as low risk during pregnancy and the remaining 74 (83%) occurred inn the group of 1430 infants (18%) born in the high-risk group. Seizures during the first weekk of life occurred in 12 of all 8055 children (1.5 per 1000); seven of these were term birthss and occurred within 48 h (0.9 per 1000). Dennis and Chalmers, who proposed thee incidence of neonatal seizures as a standard for measuring the quality of perinatal care,, registered in the UK an overall incidence of convulsions of 4.2 per 1000 births andd 1.7 per 1000 in term neonates within 48 h after birth [13]. In an Irish study the incidencee was 3.0 per 1000 births [14].
Inn a Wormerveer subgroup of 175 consecutive, non-selected pregnancies, the arter-iall umbilical cord pH and a neurological examination (Prechtl-Beintema method) weree performed, using strictly standardised methods. In nulliparous women, who de-liveredd under the responsibility of a midwife (primary care), the mean arterial pH va-luee was higher compared to nulliparous women who delivered under responsibility of ann obstetrician (secondary care) and the results were 7.27 and 7.20 respectively [15]. Onee of the 45 first-born neonates under primary care had a suboptimal neurological score,, a very low incidence [16].
Remarkably,, these results were obtained in spite of a low rate of intervention. In the totall group of 7980 women in the Wormerveer study, only in 110 women (1.4%) a cae-sareann section was performed. In the low-risk group not referred during pregnancy (7V=6613)) 29 neonates were delivered by caesarean section (0.4%). At least this study suggestedd that midwives were very able to select from the initially low-risk group cases withh elevated risk for mortality and morbidity.
1.3.2.1.3.2. The normal pregnancy study by Berghs and Spanjaards
Berghss and Spanjaards performed neurological examination in 1034 neonates in low-riskk pregnancies in 1984/1985 [17]. Of these low-risk women, 26% preferred deliv-eryy under the responsibility of an obstetrician (elective reasons). The neurological con-ditionss of these neonates were comparable, but in women who chose to deliver under responsibilityy of an obstetrician the intervention rate was more than two times higher (caesareann section and operative vaginal delivery 16.0 vs 6.4%).
1.3.3.1.3.3. The OBINT study
Pell en Heres performed a nationwide study on all 92 491 women who were initially loww risk and entered prenatal care at midwife's practices in 1990. They showed an in-creasee in caesarean section rate comparing the groups with exclusively primary care, referredd during pregnancy and labour. Women referred during pregnancy and labour subsequentlyy had a very high instrumental vaginal delivery rate of 12.8 and 31.4% re-spectively.. They also showed a time trend in referral rate: in the past decades the refer-rall rate had increased, especially the referrals during labour. Comparing OBINT with thee 'Wormerveer study' (1969-1983) referral rate during delivery was tripled [18]. OtherOther studies
Recentlyy in various European countries perinatal mortality was evaluated [19]. Muchh to our concern these results showed that the national perinatal mortality rate inn the Netherlands was higher compared to (most) other European countries (Tables
1.22 and 1.3).
Comparisonn of data was complicated by varying definitions for fetal mortality, lackk of provision of neonatal mortality data by birth weight and gestational age, lack off standardisation for age, parity and multiple pregnancies and likely biased databases
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Inn the Netherlands, evaluation of perinatal mortality is hampered by the lack of perinatall audits, which are not performed on a regular basis. Moreover, in contrast too the UK and Scandinavia, the lack of a complete and comprehensive system of ob-stetricc registration makes insight in perinatal data impossible.
Wee conclude that the Dutch system of perinatal care is based on risk selection. The manuall guiding of this selection is based upon evidence where possible, however on severall topics the evidence is scarce orr absent and the guidelines are therefore author-ityy based.
Itt is conceivable that obstetricians are afraid of making alpha errors, i.e. that the systemm will label high-risk women as low risk, and midwives are afraid of beta errors, i.e.. that the system will label low-risk women as high risk.
Withinn the observational context of this study we will try to address empirically the effectivenesss of risk selection.
Thee aim of this thesis is to answer the following questions:
(1)) What is the quality of the risk selection system, and subsequently low-risk care by midwivess and high-risk care by obstetricians?
(1.1)) Are all low-risk women recognised and do they receive primary care? (1.2)) Do the referral rates increase?
(1.3)) Are all high-risk women recognised and do they receive secondary care? (1.3.1)) Is obstetric outcome consistent with the risk selection?
(1.3.2)) Are growth-retarded fetuses detected during antenatal care, and are thee mothers referred to secondary care? How is the quality of Dutch obstetricc care regarding the detection of intrauterine growth retarda-tion? ?
(2)) What factors contribute to the relatively high perinatal mortality in the Nether-lands? ?
(3)) What is the value of various official 'medical indications', designating women as highh risk and therefore requiring secondary care?
(4)) What are the risk factors for postpartum haemorrhage and the recurrence risk? Alll questions are to be answered on an observational base, paying attention to un-avoidablee issues of bias and confounding.
OUTLINEE O F THE THESIS
Chapterr 2 gives the outlines of the ZAVIS cohort, a population-based complete re-gionall (Zaanstreek) cohort of initially low-risk pregnancies (women entering prenatal caree at a midwife's practice), and initially high-risk pregnancies (women entering
pre-natall care at the obstetricians' practice). It describes the contents of the obstetric data-base,, the study design and justification of the completeness of the cohort.
Chapterr 3 describes an empirical analysis of obstetric care in the ZAVIS cohort, as ann example of Dutch obstetric care. The risk selection process results in subdivision of threee groups in both nulliparous and multiparous women: those of initially high risk, highh risk after referral during pregnancy, and low risk at the start of labour. We evalu-atee if risk selection is conform the national guidelines as recommended during that period.. We compare referral rate and the risk selection process in a historical perspec-tivee by comparing results with the 'Wormerveer study'. We also compare our results withh national data during the same period from the national database as described byy the SIG (1993) and in the thesis of Pel and Heres, who described referral rate in thee national initially low-risk cohort in 1990.
Chapterr 4 studies adverse obstetric outcome like obstetric interventions, maternal andd neonatal morbidity in relation to risk status. Good selection would result in low interventionn rates and low rate of adverse obstetric outcome in the group of women allocatedd to low risk at the start of labour, compared to those women who were se-lectedd as initially high risk and those referred during pregnancy due to risk factors.
Chapterr 5 studies the effectiveness of detection of intrauterine growth retardation (IUGR)) both in primary and in secondary care. Intrauterine growth retardation is an importantt cause of perinatal morbidity and mortality. When IUGR is detected, inves-tigationn of possible causes and intensive fetal surveillance should take place, to prevent hypoxiaa with ensuing perinatal morbidity and mortality.
Chapterr 6 focuses on perinatal mortality rate in the ZAVIS cohort. Is perinatal mortalityy rate as high as described recently for the complete national database?
Doo maternal age, multiple pregnancies and ethnicity influence perinatal mortality rate?? Furthermore, to what extent do the restrictive management in the Netherlands in thee treatment of extremely preterm infants and the restrictive policy in prenatal screen-ingg for lethal and chromosomal abnormalities, contribute to perinatal mortality rate? Andd last but not least we discuss the influence on perinatal mortality rate as result of thee Dutch obstetric care system by describing substandard care factors in singleton pregnancies,, including the level of care.
Chapterr 7 describes the outcome of the medical indication previous caesarean. Whatt are the rates of trial of labour (TOL)? How often does trial of labour succeed, andd what factors influence success rate? What is the rate of vaginal birth after caesar-eann (VBAC), being the outcome of TOL rate and success rate? In daily practice there is aa tendency to refer women with a caesarean scar back to primary care for antenatal visits.. Is this practice justified?
Chapterr 8 investigates the rationale of the medical indication previous preterm birth. .
Inn almost all epidemiologic studies preterm births are studied as a homogeneous group.. However there is an important difference between spontaneous preterm births, andd induced preterm births (e.g. caesareans done for fetal distress in case of severe
growthh retardation). We concentrated on spontaneous preterm births (SPB), the recur-rencee risk thereof, and factors influencing the recurrence risk.
Chapterr 9 explores postpartum haemorrhage (PPH) in nulliparous women: inci-dencee and risk factors in low- and high-risk women. PPH is to be classified as standard (>5000 ml) and severe (>1000 ml). PPH, especially severe PPH is considered as one of thee unforeseeable hazards of obstetrics, and an argument against home delivery. What iss the incidence? What are the risk factors?
Chapterr 10 elaborates on the recurrence risk of postpartum haemorrhage, a pro-spectivee follow-up study of the recurrence risk after a previous postpartum haemor-rhagee and retained placenta, and the risk factors influencing the recurrence risk. Whatt is the risk of recurrence of PPH not due to retained placenta?
Chapterr 11 summarizes the results of the ZAVIS study on the Dutch selection sys-temm of obstetric care and the validity of various 'medical indications'. Recommenda-tionss are made on improvement of the effectiveness of the selection process.
References s [i i [2 2 [3. . [4; ; [5 5 [6 6 U U [8. . [9. . [io; ; [ii i [12 2 [13 3 [i4; ; [15 5
Trefferss PE, Eskes M, Kleiverda G, van Alten D. Home births and minimal medical interventions JAMAA 1990;264:2203-8.
Wildmann K, Blondel B, Nijhuis J, Defoort P, Bakoula C. European indicators of health care during pregnancy,, delivery and postpartum period. Eur J Obstet Gynecol Reprod Biol 2003; 111 :S53-65. Werkgroepp Bijstelling Kloostermanlijst. List of Obstetric Guidelines, Verloskundige Indicatielijst. Am-stelveen:: Ziekenfondsraad, 1987. Verloskundig vademecum. Amstelveen: Ziekenfondsraad, 1999. Ver-loskundigg vademecum 2003. Diemen: College voor Zorgverzekeringen, 2003.
Offerhauss PM, Anthony S, Oudshoorn CGM et al. De thuisbevalling in Nederland. Eindrapportage: 1995-2000.. Leiden: TNO Preventie en Gezondheid, 2002. TNO-rapport PG/JGD/2001.235.
Breyerr HBG. Stolk JG. Enkele beschouwingen naar aanleiding van een onderzoek over doodgeboorte inn het jaar 1961. Ned Tijdschr Geneeskd 1971 ;115:1638 46.
Smitss F. De doeltreffendheid van het selectiesysteem binnen de verloskundige zorg. Thesis, Catholic Universityy Nijmegen, 1981.
Eskess TKAB, Jongsma HW, Houx PCW. Umbilical cord gases in home deliveries versus hospital-based deliveries.. J Reprod Med 1981;26:405-8.
Lievaartt M, de Jong PA. Neonatal morbidity in deliveries conducted by midwives and gynecologists: a studyy of the system prevailing in the Netherlands. Am J Obstet Gynecol 1982;144:376-86.
Mcnaglee RN. Relationship of birth outcome to health care provider. Am J Obstet Gynecol 1983;146:870-1. .
Trefferss PE, van Alten D, Pel M. Condemnation of obstetric care in the Netherlands? Am J Obstet Gy-necoll 1983;46:871-2.
vann Alten D, Eskes M, Treffers PE. Midwifery in the Netherlands. The Wormerveer study; selection, modee of delivery, perinatal mortality and infant morbidity. Br J Obstet Gynaecol 1989;96:656-62. Eskess M. Het Wormerveeronderzoek. Meerjarenonderzoek naar de kwaliteit van de verloskundige zorg rondd een vroedvrouwenpraktijk. Thesis, University of Amsterdam, 1989.
Denniss J, Chalmers I. Very early neonatal seizure rate: a possible epidemiologic indicator of the quality off perinatal care. Br J Obstet Gynaecol 1982;89:418-26.
MacDonaldd D, Grant A, Sheridon-Pereira M, Boylan P, Chalmers I. The Dublin randomized con-trolledd trial of intrapartum fetal heart rate monitoring. Am J Obstet Gynecol 1985;152:524-39. Knuistt M, Eskes M, van Alten D. De pH van het arteriole navelstrengbloed van pasgeborenen bij door vroedvrouwenn geleide bevallingen. Ned Tijdschr Geneeskd 1987; 131:362-5.
[16]] Eskes M, Knuist M, van Alten D. Neurologisch onderzoek bij pasgeborenen in een vroedvrouwenprak-tijk.. Ned Tijdschr Geneeskd 1987;131:1040-3.
[17]] Berghs G, Spanjaards E. De normale zwangerschap: bevalling en beleid. Thesis, Catholic University Nijmegen,, 1988.
[18]] Pel M, Heres MHB. OBINT. A study of obstetric intervention. Thesis, University of Amsterdam, 1995. [19]] Buitensdijk S, Zeitlin J, Cuttini M, Langhoff-Roos J, Bottu J. Indicators of fetal and infant health
