Outcomes of induction versus spontaneous onset of labour at 40 and 41 GW: findings from a prospective database, Sri Lanka

OBJECTIVES: The World Health Organization recommends induction of labour (IOL) for low risk pregnancy from 41 + 0 gestational weeks (GW). Nevertheless, in Sri Lanka IOL at 40 GW is a common practice. This study compares maternal/newborn outcomes after IOL at 40 GW (IOL40) or 41 GW (IOL41) versus spontaneous onset of labour (SOL). METHODS: Data were extracted from the routine prospective individual patient database of the Soysa Teaching Hospital for Women, Colombo. IOL and SOL groups were compared using logistic regression. RESULTS: Of 13,670 deliveries, 2359 (17.4%) were singleton and low risk at 40 or 41 GW. Of these, 456 (19.3%) women underwent IOL40, 318 (13.5%) IOL41, and 1585 (67.2%) SOL. Both IOL40 and IOL41 were associated with an increased risk of any maternal/newborn negative outcomes (OR = 2.21, 95%CI = 1.75–2.77, p < 0.001 and OR = 1.91, 95%CI = 1.47–2.48, p < 0.001 respectively), maternal complications (OR = 2.18, 95%CI = 1.71–2.77, p < 0.001 and OR = 2.34, 95%CI = 1.78–3.07, p < 0.001 respectively) and caesarean section (OR = 2.75, 95%CI = 2.07–3.65, p < 0.001 and OR = 3.01, 95%CI = 2.21–4.12, p < 0.001 respectively). Results did not change in secondary and sensitivity analyses. CONCLUSIONS: Both IOL groups were associated with higher risk of negative outcomes compared to SOL. Findings, potentially explained by selection bias, local IOL protocols and CS practices, are valuable for Sri Lanka, particularly given contradictory findings from other settings. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-022-04800-1.