Twin-to-twin transfusion syndrome : from placental anastomoses to
long term outcome
Lopriore, E.
Citation
Lopriore, E. (2006, September 13). Twin-to-twin transfusion syndrome : from placental
anastomoses to long term outcome. Retrieved from https://hdl.handle.net/1887/4556
Version:
Corrected Publisher’s Version
License:
Licence agreement concerning inclusion of doctoral thesis in the
Institutional Repository of the University of Leiden
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C h a p t e r 1
Introduction
Twins, especially identical twins, have fascinated humanity over the cen-turies. In perinatology, however, fascination for the twinning process is often outweighed by concerns due to increased medical complications associated with twin pregnancies. Perinatal mortality and morbidity in twins is significantly increased compared to singletons, partly due to a higher incidence of prematurity and very low birth weight in twins1.
Mortality is reported to be 3 to 7-fold higher in twins than in singletons2,
whereas morbidity, particularly risk of cerebral palsy, is 7-fold higher in twins than in singletons1. Risk of adverse outcome is particularly
pro-nounced in monochorionic twins. Perinatal mortality in monochorionic twins is 2.5-fold higher than in dichorionic twins3, whereas neurological
morbidity is 7-fold higher in preterm monochorionic twins than in preterm dichorionic twins4. Adverse outcome in monochorionic twinning is due to
complications associated with the presence of placental vascular anasto-moses.
Vascular anastomoses are extremely rare in dichorionic placentas but ubiquitous in monochorionic placentas5, and may lead, amongst other
complications, to twin-to-twin transfusion syndrome (TTTS). TTTS occurs in approximately 15% of monochorionic twin pregnancies6. TTTS usually
develops during the 2nd trimester of pregnancy, resulting in hypovolemia,
oliguria and oligohydramnios in the donor twin and hypervolemia, polyuria and polyhydramnios in the recipient twin6. TTTS is associated with high
perinatal mortality and morbidity. In the past, diagnosis of TTTS was based on neonatal criteria such as birth weight discordance and hemo-globin difference. Nowadays, diagnosis of TTTS is reached strictly on prenatal ultrasound criteria. The main diagnostic criterion for TTTS is the twin oligo-polyhydramnios sequence (TOPS). A significant evolution in prenatal care strategies and management options for patients with TTTS has occurred during the last decade. The two main therapeutic options in TTTS are serial amniodrainage and fetoscopic laser occlusion of commu-nicating placental vascular anastomoses6. Fetoscopic laser surgery is a new
treatment modality that has led to an increase in survival rates. In perina-tology, a decrease in mortality rates may be associated with an increase in morbidity rates. Follow-up studies in infants with TTTS are shedding more
General introduction | Chapter 1
light on the wide range of morbidity associated with TTTS, such as neuro-logical, cardiac and renal sequelae.
Since monochorionic twinning is known to occur worldwide in 1 in every 400 pregnancies6, the estimated number of TTTS cases in The Netherlands
is approximately 75 cases per year. The majority of TTTS cases in The Netherlands are referred to the Leiden University Medical Center (LUMC). The LUMC is a tertiary medical center and serves as the national referral center for fetal therapy, including fetoscopic laser surgery for TTTS. The laser surgery program at the LUMC started in August 2000.
Outline of the thesis
In June 2002 the Leiden’s TTTS study (LETTS’ study) was started. The aim of this prospective study was to investigate the short-term and long-term outcome in TTTS treated with fetoscopic laser surgery. With an intense and ongoing collaboration between the obstetric and neonatology depart-ments of the LUMC, several other study projects associated with the patho-genesis, diagnosis and treatment of TTTS were also initiated. The aim of these studies can be summarized as follows:
Chapter 2 - Review of the literature on TTTS. This review analyzes the
pos-sible pathophysiologic mechanisms involved, discusses the latest findings in diagnosis, therapy and prognosis, and focuses on neonatal and pediatric morbidity associated with TTTS.
Chapter 3 - Description of a novel technique to determine the net feto-fetal
blood flow through placental arterio-venous anastomoses in a unique case of TTTS.
Chapter 4 - Study on the role of velamentous umbilical cord insertion and
discordant placental territories in the pathogenesis of TTTS by comparing monochorionic placentas with and without TTTS.
Twin-to-twin transfusion syndrome: from placental anastomoses to long-term outcome
Chapter 5 - Study on the frequency of residual placental vascular
anasto-moses after fetoscopic laser surgery for TTTS in relation to associated risks and outcome.
Chapter 6 - Description of a new form of TTTS, named twin
anemia-polycy-themia sequence (TAPS), not associated with the characteristic twin oligo-polyhydramnios sequence (TOPS) found in TTTS.
Chapter 7 - Study on hemoglobin differences at birth in monochorionic
twins without TTTS compared to a control group of dichorionic twins, in relation to birth order and placental vascular anatomy.
Chapter 8 - Study on the neonatal outcome in TTTS survivors treated with
fetoscopic laser surgery compared to a control group of monochorionic twins without TTTS.
Chapter 9 - Study on the short-term neurological outcome in TTTS
sur-vivors treated with fetoscopic laser surgery compared to a control group of monochorionic twins without TTTS, using cranial ultrasonography.
Chapter 10 - Study on the short-term cardiac outcome in TTTS survivors
treated with fetoscopic laser surgery compared to a control group of monochorionic twins without TTTS, using echocardiography.
Chapter 11 - Study on the long-term outcome in TTTS treated conservatively
at the LUMC between January 1990 and December 1998.
Chapter 12 - Study on the long-term outcome in TTTS treated with
feto-scopic laser surgery at the LUMC between August 2000 and December 2003.
Chapter 13 - General discussion concerning the results of these studies. Chapter 14 - Future perspectives and proposals for future research.
General introduction | Chapter 1
