Twenty-five studies were included in the review; 16 RCTs (7,001 patients, range 22 to 3,407), three quasi-randomised trials (658 patients, range 100 to 402), and six observational studies (at least 5,574 patients, range 254 to 3,914 where reported). Seven RCTs reported allocation concealment (reported as adequate in three), one trial reported blinding and six trials indicated intention-to-treat analyses was performed.
No significant between-group difference was found for stillbirth (RR 0.29, 95% CI 0.06 to 1.38; Ι²=0%, 14 RCTs); 10 RCTs had no reported events. Subgroup analyses for induction of labour at 41 weeks remained statistically insignificant for incidence of stillbirth (RR 0.29, 95% CI 0.06 to 1.38; Ι²=0%, 12 RCTs). No estimate was possible for induction of labour at 42 weeks. Elective induction of labour for post-term pregnancies beyond 41 weeks gestation significantly reduced (all-cause) perinatal mortality compared with expectant management (RR 0.31, 95% CI 0.11 to 0.88; Ι²=0%, 14 RCTs). Six of the included RCT had no reported events. Results remained statistically significant for induction of labour at 41 weeks (RR 0.27, 95% CI 0.08 to 0.98; Ι²=0%, 12 RCTs), but no significant between-group difference was found for induction of labour at 42 weeks (RR 0.41, 95% CI 0.06 to 2.73; Ι²=0%, two RCTs). The total number of reported events for the primary outcomes was low.
Elective induction of labour significantly reduced the incidence of meconium aspiration syndrome (RR 0.43, 95% CI 0.23 to 0.79; Ι²=0%, seven RCTs) and macrosomia (RR 0.72, 95% CI 0.54 to 0.98; Ι²=71%, seven RCTs), but no significant difference was found for birth asphyxia (two RCTs).
Results from individual quasi-randomised trials and observational studies were also reported; evidence from these studies was mixed, approximately half the studies demonstrated a significant difference in the rate of stillbirths and/or perinatal mortality for active compared with expectant management.