Marginal Sinus and Bleeding in Women with a Low-Positioned Placenta: A Narrative Synthesis Systematic Review

To ascertain the impact of marginal sinus on the risk of antepartum, intrapartum, and postpartum hemorrhage in women with a low-positioned placenta.

PubMed, Scopus, EMBASE, and the Cochrane Library databases (1980-2024).

Systematic reviews and quantitative primary research studies reporting a diagnosis of low-positioned placenta with the presence or absence of marginal sinus. Outcome measures: antepartum, intrapartum, and postpartum hemorrhage.

Of the 8140 articles screened for eligibility, 171 were sought for full-text review, and 6 were included for analysis. The systematic review comprises six cohort studies, two prospective and four retrospective, for a total of 621 women with a low-positioned placenta. Five studies assessed the impact of marginal sinus on antenatal hemorrhage, two examined its influence on intrapartum hemorrhage, and one study also evaluated postpartum hemorrhage.

The studies displayed adequate representativeness of exposed individuals. Limitations included retrospective design with a small sample size, different gestational ages at diagnosis of low-positioned placenta, and substantial heterogeneity in outcomes.

Among the five studies examining the relationship between marginal sinus and antepartum bleeding, a significant association was reported in four, while one found no such link. The only two studies examining the relationship between marginal sinus and intrapartum hemorrhage reported no association. Additionally, one of these studies identified lower rates of postpartum bleeding in women with normally located placental tissue and a marginal sinus reaching the internal os, compared with women with low-positioned placental tissue. The risk of bleeding in women with a low-positioned placenta and marginal sinus is still poorly evaluated. The evidence from the included studies lacked consistency and conclusive findings, highlighting the need for further research to elucidate this association and inform clinical management effectively. Additionally, studies failed to address the significance of marginal sinus in diagnosing and managing low-positioned placenta.