Severe maternal morbidity in preterm cesarean delivery: A systematic review and meta-analysis

•The incidence of extremely preterm cesarean delivery has increased.•Gestational age under 26 weeks is associated with an increased risk of severe maternal morbidity.•Physicians should be aware of this risk to improve shared decision-making process. More than half of extremely preterm infants are delivered by cesarean section. Few data are available about severe maternal morbidity (SMM) of these extremely preterm cesarean. The objective was to determine whether gestational age under 26 weeks of gestation (weeks) was associated with an increased risk of SMM compared with gestational age between 26 and 34 weeks in women having a cesarean delivery. We searched MEDLINE, ISI Web of Science, the Cochrane Database, PROSPERO, and ClinicalTrials.gov on January 31, 2020. The search strategy clustered terms describing SMM and preterm cesarean delivery. No restrictions on language, publication status, and study design were applied. Abstracts were included if there was sufficient information to assess study quality. The authors of all identified studies were contacted to request for aggregated data. Relative risks (RR) were calculated using the inverse variance method. The primary outcome was SMM as defined in each study. We analyzed data on preterm cesarean deliveries between 22 and 34 weeks. The protocol was registered in PROSPERO (registration: CRD42019128644). Six studies involving 45,572 women (3,440 delivering < 26 weeks; 42,132 delivering between 26 and 34 weeks) were included. SMM occurred in 607 women (17.6 %) < 26 weeks and 4,483 women (10.6 %) between 26 and 34 weeks. Gestational age < 26 weeks was associated with an increased risk of SMM (RR, 1.65; 95 % CI [Confidence Interval], 1.52–1.78; I2 = 40 %). Gestational age < 26 weeks remained associated with SMM in the subgroup analyses depending on the type of the study (prospective or retrospective), country of the study (European or non-European), and high quality of the study. A sensitivity analysis showed that gestational age < 25 weeks was also associated with SMM in preterm cesarean delivery (RR, 1.66; 95 % CI, 1.50–1.83; I2 = 3%). Gestational age < 26 weeks was associated with an increased risk of SMM in women having a preterm cesarean delivery. Obstetricians and neonatologists should be aware of the increased risk of SMM in cesarean.