Prevalence, Risk Factors and Outcomes of Velamentous and Marginal Cord Insertions: A Population-Based Study of 634,741 Pregnancies

741 Pregnancies. PLoS ONE 8(7): e70380. doi:10.1371/journal.pone.0070380 Prevalence, Risk Factors and Outcomes of Velamentous and Marginal Cord Insertions: A Population-Based Study of 634,741 Pregnancies Cathrine Ebbing 0 Torvid Kiserud 0 Synnve Lian Johnsen 0 Susanne Albrechtsen 0 Svein Rasmussen 0 Vikrant Sahasrabuddhe, Vanderbilt University, United States of America 0 1 Department of Obstetrics and Gynaecology, Haukeland University Hospital , Bergen , Norway , 2 Clinical Foetal Physiology Research Group, Department of Clinical Science, University of Bergen , Norway Objectives: To determine the prevalence of, and risk factors for anomalous insertions of the umbilical cord, and the risk for adverse outcomes of these pregnancies. Design: Population-based registry study. Population: All births (gestational age .16 weeks to ,45 weeks) in Norway (623,478 singletons and 11,263 pairs of twins). Methods: Descriptive statistics and odds ratios (ORs) for risk factors and adverse outcomes based on logistic regressions adjusted for confounders. Main outcome measures: Velamentous or marginal cord insertion. Abruption of the placenta, placenta praevia, preeclampsia, preterm birth, operative delivery, low Apgar score, transferral to neonatal intensive care unit (NICU), malformations, birthweight, and perinatal death. Results: The prevalence of abnormal cord insertion was 7.8% (1.5% velamentous, 6.3% marginal) in singleton pregnancies and 16.9% (6% velamentous, 10.9% marginal) in twins. The two conditions shared risk factors; twin gestation and pregnancies conceived with the aid of assisted reproductive technology were the most important, while bleeding in pregnancy, advanced maternal age, maternal chronic disease, female foetus and previous pregnancy with anomalous cord insertion were other risk factors. Velamentous and marginal insertion was associated with an increased risk of adverse outcomes such as placenta praevia (OR = 3.7, (95% CI = 3.1-4.6)), and placental abruption (OR = 2.6, (95% CI = 2.1-3.2)). The risk of pre-eclampsia, preterm birth and delivery by acute caesarean was doubled, as was the risk of low Apgar score, transferral to NICU, low birthweight and malformations. For velamentous insertion the risk of perinatal death at term was tripled, OR = 3.3 (95% CI = 2.5-4.3). Conclusion: The prevalence of velamentous and marginal insertions of the umbilical cord was 7.8% in singletons and 16.9% in twin gestations, with marginal insertion being more common than velamentous. The conditions were associated with common risk factors and an increased risk of adverse perinatal outcomes; these risks were greater for velamentous than for marginal insertion. - Velamentous cord insertion is diagnosed when the umbilical vessels insert into the membranes before they reach the placental margin. This results in the umbilical vessels lacking the protection of Whartons jelly for the section between the insertion and the placental margin. A marginal cord insertion is where this distance is reduced to a minimum, but the insertion site is supported by very little placental tissue. Velamentous insertion of the umbilical cord has been associated with an increased risk of adverse perinatal outcomes [13]. Velamentous vessels are associated with vasa praevia (where the vessels traverse the internal os of the cervix in front of the leading foetal part), a condition that is associated with high perinatal mortality when it is not diagnosed prenatally [4]. Therefore, ultrasound screening for vasa praevia in high-risk populations (e.g. twin pregnancies and pregnancies conceived with the aid of assisted reproductive technology) has been suggested as a cost-effective measure [5], but a better understanding of velamentous and marginal cord insertions is needed [6]. Abnormal cord insertion seems to be associated with impaired development and function of the placenta, and thus influences foetal growth [7,8] and has been linked to placenta praevia and pregnancy-induced hypertension [3]. The altered development of the placenta with anomalous cord insertion may influence the relationship between birthweight and placental weight, but this has yet to be confirmed. Neither is it known whether there is an increased risk of recurrence of anomalous cord insertion in a subsequent pregnancy. The existing data on risk factors and perinatal outcome in pregnancies with anomalous cord insertion are conflicting [2,9]. Velamentous and marginal insertions are reported to occur in 0.5 2.4% and 8.5% of all pregnancies, respectively [2,3,10], with the prevalence being higher in multiple pregnancies [11] and in pregnancies conceived with the aid of assisted reproductive technology [12]. However, these prevalence rates are derived from hospital registers, which might be influenced by selection bias, and population-based studies are lacking. The aims of the present study were thus 1: to establish a population-based prevalence of velamentous and marginal insertions of the umbilical cord, 2: to identify risk factors for anomalous cord insertion, and 3: assess the risk for adverse perinatal outcomes associated with these conditions. Materials and Methods Ethics Statement The Regional Committee for Medical and Health Research Ethics West approved the study protocol (approval no. REC West 2011/949), and waived the need for written informed consent form the participants, since the data were analysed anonymously. A population-based registry study was performed of all singleton births at gestational weeks 1645 in Norway during the period 19992009 using data from the Medical Birth Registry of Norway. Twin pregnancies were also studied. Registration of birth is compulsory in Norway, and the registry contains information on all births since 1967 based on information taken from a form completed by the attending midwife or physician shortly after delivery. Information regarding whether the umbilical cord insertion into the placenta was normal, marginal, velamentous, or had vessel anomalies was requested on the form used since 1999. The attending midwife weighs the placenta with the membranes and umbilical cord attached. The registry also holds information regarding the maternal health before and during pregnancy, paternal age, delivery, placental weight, birthweight and perinatal outcomes. Voluntary notification of all pregnancies conceived with the aid of assisted reproductive technology has been included in the registry since 1988; the inclusion of this information became compulsory since 2001. The gestational age (in weeks) was based on ultrasound dating when available (96.8%), and otherwise based on the mothers last menstrual period. Smoking habits were registered after obtaining informed consent. The information of smoking habits at the start of pregnancy was collected at the first prenatal visit. Perinatal mortality was defined as death before birth or within 7 days after birth. Parity was defined as the number of previous deli (...truncated)