BACKGROUND: The benefits and harms of early induction of labour to reduce shoulder dystocia in fetuses suspected to be large for gestational age (LGA) are uncertain. We aimed to investigate whether early induction of labour is associated with a reduced risk of shoulder dystocia compared with standard care. METHODS: In this open-label, randomised controlled phase 3 trial, women aged ≥18 years with a suspected LGA fetus (estimated fetal weight >
90th customised percentile) as identified by ultrasound scan between 35 weeks and 0 days (35 FINDINGS: Between June 8, 2018, and Oct 25, 2022, 2893 women were randomly assigned to induction of labour (n=1447) or standard care (n=1446)
the trial was terminated before the target of 4000 participants was reached on advice of the data monitoring committee following the lower-than-expected incidence of shoulder dystocia in the standard care group. Two participants in the induction group and seven in the standard care group had missing data for the primary outcome and were excluded from the ITT analysis. In the ITT analysis, 33 (2·3%) of 1445 babies in the induction group versus 44 (3·1%) of 1439 in the standard care group had shoulder dystocia (risk ratio [RR] 0·75 [95% CI 0·51-1·09]
p=0·14) with a mean difference of -6·0 days' (95% CI -6·3 to -5·6) gestation and -163·6 g (-190·0 to -137·1) birthweight between trial groups. 355 (24·6%) of 1446 mothers in the standard care group were induced, delivered, or went into labour at or before 38 INTERPRETATION: No significant difference in incidence of shoulder dystocia was found between trial groups in the ITT analysis, probably due to the high proportion of earlier-than-expected deliveries in the standard care group reducing the intended between-group differences in gestational age and birthweight. However, in the per-protocol analysis, compared with all deliveries after 38 FUNDING: National Institute for Health and Care Research Health Technology Assessment Programme.