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

ObjectivesTo determine the prevalence of, and risk factors for anomalous insertions of the umbilical cord, and the risk for adverse outcomes of these pregnancies.DesignPopulation-based registry study.SettingMedical Birth Registry of Norway 1999–2009.PopulationAll births (gestational age >16 weeks to MethodsDescriptive statistics and odds ratios (ORs) for risk factors and adverse outcomes based on logistic regressions adjusted for confounders.Main outcome measuresVelamentous or marginal cord insertion. Abruption of the placenta, placenta praevia, pre-eclampsia, preterm birth, operative delivery, low Apgar score, transferral to neonatal intensive care unit (NICU), malformations, birthweight, and perinatal death.ResultsThe 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).ConclusionThe 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.

研究目的：本研究旨在明确脐带异常插入的患病率及其相关危险因素，并探讨此类妊娠的不良结局发生风险。
研究设计：基于人群的登记研究。
研究场景：1999年至2009年挪威医学出生登记系统。
研究人群：所有妊娠孕周大于16周的分娩病例。
研究方法：采用描述性统计方法，以及针对混杂因素校正后的logistic回归分析，计算危险因素与不良结局的比值比（OR）。
主要结局指标：脐带帆状插入（velamentous cord insertion）与脐带边缘插入（marginal cord insertion）；胎盘早剥、前置胎盘、子痫前期、早产、手术分娩、低Apgar评分、转入新生儿重症监护病房（NICU）、胎儿畸形、出生体重以及围产期死亡。
研究结果：单胎妊娠中，脐带异常插入的患病率为7.8%（其中帆状插入占1.5%，边缘插入占6.3%）；双胎妊娠中患病率为16.9%（帆状插入占6%，边缘插入占10.9%）。两种异常插入类型共享共同危险因素：双胎妊娠、辅助生殖技术受孕为最主要的危险因素，此外还包括妊娠期出血、产妇高龄、产妇慢性疾病、胎儿为女性以及既往有脐带异常插入妊娠史。脐带帆状插入与边缘插入均与不良结局风险升高相关，例如前置胎盘（OR=3.7，95%CI=3.1~4.6）与胎盘早剥（OR=2.6，95%CI=2.1~3.2）。子痫前期、早产与急诊剖宫产分娩的风险升高至原来的2倍，低Apgar评分、转入NICU、低出生体重以及胎儿畸形的风险亦呈类似升高趋势。对于脐带帆状插入者，足月妊娠时的围产期死亡风险升高至3倍，OR=3.3（95%CI=2.5~4.3）。
结论：脐带帆状插入与边缘插入的患病率在单胎妊娠中为7.8%，双胎妊娠中为16.9%，其中边缘插入较帆状插入更为常见。此类脐带异常与共同的危险因素相关，且会升高围产期不良结局的发生风险；帆状插入者的相关风险高于边缘插入者。