Velamentous cord insertion: results from a rapid review of incidence, risk factors, adverse outcomes and screening

Abstract

Background: Velamentous cord insertion (VCI) is an umbilical cord attachment to the membranes surrounding the placenta instead of the central mass. VCI is strongly associated with vasa praevia (VP), where umbilical vessels lie in close proximity to the internal cervical os. VP leaves the vessels vulnerable to rupture, which can lead to fatal fetal exsanguination. Screening for VP using second-trimester transabdominal sonography (TAS) to detect VCI has been proposed. We conducted a rapid review investigating the quality, quantity and direction of evidence available on the epidemiology, screening test accuracy and post-screening management pathways for VCI. Methods: MEDLINE, Embase and the Cochrane Library were searched on 5 July 2016 and again on 11 October 2019, using general search terms for VP and VCI. Only peer-reviewed articles reporting on the epidemiology of VCI, the accuracy of the screening test and/or downstream management pathways for VCI pregnancies were included. Quality and risk of bias of each included study were assessed using pre-specified tools. Results: Forty-one relevant publications were identified; all but one were based on non-UK pregnancy cohorts, and most included relatively few VCI cases. The estimated incidence of VCI was 0.4-11% in singleton pregnancies, with higher incidence in twin pregnancies (1.6-40%). VCI incidence was also increased among pregnancies with one or more other risk factors, including in vitro fertilisation pregnancies or nulliparity. VCI incidence among women without any known risk factors was unclear. VCI was associated with adverse perinatal outcomes, most notably pre-term birth and emergency caesarean section in singleton pregnancies, and perinatal mortality in twins; however, associations varied across studies and the increased risk was typically low or moderate compared with pregnancies without VCI. In studies on limited numbers of cases, screening for VCI using TAS had good overall accuracy, driven by high specificity. No studies on post-screening management of VCI were identified. Conclusions: Literature on VCI epidemiology and outcomes is limited and low-quality. The accuracy of secondtrimester TAS and the benefits and harms of screening cannot be determined without prospective studies in large cohorts. Modelling studies may indicate the feasibility and value of studying the epidemiology of VCI and the potential impact of detecting VCI as part of a population screening programme for VP.

Placental abnormalities in congenital heart disease

“…Sub-group evaluation noted that the relative risk of CHD subtype in the setting of abnormal cord insertion was highest for conotruncal defects (relative risk, RR =3.08), followed by left heart disease, namely HLHS and coarctation of the aorta (RR =2.4) and right heart disease, including Ebstein anomaly, tricuspid atresia, pulmonary atresia with intact ventricular septum, and critical pulmonary stenosis (RR =2.22) (20). Abnormal cord insertions sites, particularly marginal and velamentous insertion sites, have been associated with adverse pregnancy outcomes, including preterm birth, SGA infants, low birth weight (LBW) infants, emergency cesarean delivery and intrauterine fetal death, with velamentous cord insertion sites carrying the greatest risk (22,23). Similarly, eccentric and peripheral cord insertion sites have been variably associated with SGA and LBW (24), premature birth and decreased placental weight z-score (Figure 3) (25).…”

Clinical Significance of Velamentous Cord Insertion Prenatally Diagnosed in Twin Pregnancy

“…The incidence of VCI has been reported to be 0.1–1.8% in all pregnancies [ 1 ]. An increased prevalence of VCI had been reported for twin pregnancies (1.6–40%) especially in monochorionic (MC) twin pregnancies, probably as a result of unequal sharing of the placentas [ 2 , 3 ].…”

Incidence and risk factors for velamentous umbilical cord insertion in singleton pregnancies after assisted reproductive technology

“…Therefore, it is ineluctable that the research population is small in size and selection bias is inherent in this observational retrospective cohort study. Previous studies have focused only on the linkage between maternal characteristics and VCI and classified pregnancies after ART treatment under only one category 8,12,13,18 . The strength of this study is that the association between VCI and several ART‐related variables was investigated separately.…”

“…We inferred from these reports that ART procedures could also influence placental development from conception. Velamentous umbilical cord insertion (VCI) is a relatively rare placental abnormality associated with increased risks of maternal and fetal complications, such as placenta previa, placental adhesion, preeclampsia, fetal growth restriction, and non‐reassuring fetal heart rate patterns requiring an emergency cesarean section 9–12 . Notably, a higher incidence of VCI has been reported in singleton pregnancies conceived by ART than in naturally conceived pregnancies 9,13,14 …”