Uterine synechiae in pregnancy and the risk of adverse outcomes: a systematic review and meta-analysis.

Abstract

Objectives: To evaluate the association between uterine synechiae identified on ultrasound and adverse pregnancy outcomes through a systematic review and meta-analysis of observational studies.

Data sources: A systematic search of PubMed, Cochrane Library, CINAHL and ScienceDirect was performed from database inception to July 2025 in accordance with MOOSE guidelines.

Study eligibility criteria: Cohort and case-control studies reporting pregnancy outcomes among women with versus without uterine synechiae were eligible.

Study appraisal and synthesis methods: Two reviewers independently screened studies, extracted data and assessed quality using the Newcastle-Ottawa Scale. Random-effects models were used to calculate pooled odds ratios and mean differences for maternal and neonatal outcomes.

Results: Four studies met inclusion criteria, comprising 628 pregnancies with uterine synechiae and 65,959 controls. Uterine synechiae were associated with an increased risk of preterm birth <37 weeks (odds ratio 1.80; 95% CI 1.35-2.39), preterm premature rupture of membranes (odds ratio 3.58; 95% CI 1.13-11.36), placental abruption (odds ratio 3.34; 95% CI 1.57-7.13) and placenta previa (odds ratio 3.19; 95% CI 1.07-9.57). Mean birth weight was significantly lower among affected pregnancies (mean difference -154.29 g; 95% CI -259.20 to -49.38). No significant differences were observed for preterm birth <34 weeks, overall cesarean delivery, fetal growth restriction, stillbirth or NICU admission. A subgroup analysis demonstrated higher odds of cesarean delivery for fetal malpresentation in pregnancies with synechiae (odds ratio 1.97; 95% CI 1.23-3.13).

Conclusions: Uterine synechiae identified on ultrasound are associated with increased risks of preterm birth, PPROM, placental abruption, placenta previa and fetal malpresentation, as well as lower birth weight. These findings indicate that synechiae are not incidental findings and support their association with adverse outcomes in pregnancy.