Impact of marginal cord insertion on perinatal outcomes: a systematic review and meta-analysis

Despite its high prevalence and the possible link with perinatal complications, marginal cord insertion is surrounded by considerable controversy regarding management. This meta-analysis aimed to study its association with several perinatal outcomes in a manner that provides trustworthy and exact effect measures, enabling us eventually to evaluate its overall risk for pregnancy.

A systematic search was performed in Medline, Scopus, and the Cochrane Library on July 30, 2022, to identify eligible studies.

Observational studies, including singleton pregnancies and comparing MCI with central cord insertion or eccentric cord insertion, either prenatally or postnatally identified, were considered eligible.

The Newcastle-Ottawa Scale was used to assess study quality, and the Quality in Prognosis Studies tool was used to assess bias risk. The main outcome was small-for-gestational-age neonates. A Q test and an I² score were used to assess study heterogeneity. The analyses were performed using a random-effects model, and the results were expressed as relative risk or mean difference with a 95% confidence interval.

Overall, 15 studies (13 cohort studies and 2 case-control studies) contributed data to the analysis. There was a prenatal diagnosis in 7 studies and a postnatal diagnosis in 8 studies. The overall prevalence of marginal cord insertion was 6.15% (range, 1.13%-11.3%). Pregnancies with marginal cord insertion compared with pregnancies with central cord insertion were found to be at higher risk of small-for-gestational-age neonates (relative risk, 1.25; 95% confidence interval, 1.21-1.29), preeclampsia (relative risk, 1.61; 95% confidence interval, 1.54-1.67), placental abruption (relative risk, 1.53; 95% confidence interval, 1.34-1.75), stillbirth (relative risk, 1.97; 95% confidence interval, 1.02-3.78), preterm delivery (relative risk, 1.47; 95% confidence interval, 1.24-1.75), lower mean gestational age at birth (mean difference, -0.20; 95% confidence interval, -0.38 to -0.01), emergency cesarean delivery (relative risk, 1.39; 95% confidence interval, 1.35-1.44), lower mean birthweight (mean difference, -139.19; 95% confidence interval, -185.78 to -92.61), 5-minute Apgar score of <7 (relative risk, 1.48; 95% confidence interval, 1.00-2.19), and neonatal intensive care unit admission (relative risk, 1.57; 95% confidence interval, 1.20-2.06). When only pregnancies with prenatally diagnosed MCI were considered, the risk remained high regarding small for gestational age (relative risk, 1.34; 95% confidence interval, 1.21-1.48), preeclampsia (relative risk, 1.42; 95% confidence interval, 1.01-1.99), stillbirth (relative risk, 2.99; 95% confidence interval, 1.03-8.70), preterm delivery (relative risk, 1.41; 95% confidence interval, 1.19-1.68), lower mean gestational age at birth (mean difference, -0.22; 95% confidence interval, -0.33 to -0.11), and lower mean birthweight (mean difference, -122.41; 95% confidence interval, -166.10 to -78.73).

Here, the higher risk that marginal cord insertion poses for pregnancy, regarding several adverse outcomes, became evident. Many of these associations persisted among the prenatally diagnosed pregnancies. The underlining pathophysiology should be investigated, and further research is needed on the effect of increased surveillance in improving perinatal outcomes.