Effect of mode of delivery on perinatal outcome in severe preterm birth: systematic review and meta-analysis

To review the evidence on the effect of mode of delivery on perinatal outcome of fetuses born before 32 weeks' gestation.

MEDLINE, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL), the ClinicalTrials.gov registry and gray literature sources were searched, starting from the year 2000 to reflect contemporary practice in perinatal care. Non-randomized or randomized studies that included singleton fetuses without chromosomal abnormality or major congenital defect delivered vaginally or via Cesarean section were eligible for inclusion in the analysis. Primary outcomes were neonatal death, defined as death in the first 28 days of age, and survival to discharge. Secondary outcomes were other adverse perinatal events. The ROBINS-I tool was used to assess the risk of bias. The overall quality of evidence for the outcomes was assessed according to GRADE. Summary odds ratios (ORs) with 95% CIs were calculated, and random-effects models were used for data synthesis. Subgroup analysis was performed for delivery before 28 weeks, delivery between 28 and 32 weeks and according to fetal presentation at delivery.

A total of 27 retrospective studies (22 887 neonates) were included in the systematic review and meta-analysis, all of which reported on singleton pregnancies. Among cases born before 28 weeks, vaginal delivery significantly increased the risk of neonatal death of fetuses with any type of presentation (n = 1496) (OR 1.87 (95% CI, 1.05-3.35); I²  = 65%, very low quality of evidence) and of fetuses with breech presentation (n = 733) (OR 3.55 (95% CI, 2.42-5.21); I²  = 21%, moderate quality of evidence). The odds of survival to discharge were significantly decreased among fetuses with breech presentation delivered before 28 weeks (n = 646) (OR 0.36 (95% CI, 0.24-0.54); I²  = 21%, low quality of evidence). Among breech fetuses born between 28 and 32 weeks, vaginal delivery increased the odds of perinatal death (intrapartum and neonatal) (n = 1581) (OR 3.06 (95% CI, 1.47-6.35); I²  = 0%, high quality of evidence). In non-cephalic fetuses born between 24 and 32 weeks, vaginal delivery decreased the odds of survival to discharge (n = 1030) (OR 0.28 (95% CI, 0.19-0.40); I²  = 0%, moderate quality of evidence). No significant effect on mortality of mode of delivery was observed in cephalic fetuses at any gestational age.

This systematic review and meta-analysis suggests that vaginal delivery in severe preterm birth is associated with an increased risk of neonatal and perinatal death in breech fetuses, while no significant association was observed for cephalic fetuses. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.