Comparison of pregnancy outcomes between induction of labor at 40 weeks and 41 weeks in low-risk women with Singleton pregnancies: a retrospective cohort study.

Background: The best timing of delivery for term pregnancies has not been determined. This retrospective cohort study compared pregnancy outcomes between induction of labor (IOL) at 40 weeks and 41 weeks in low-risk women with singleton pregnancies and investigated maternal motivations regarding elective IOL.

Methods: A total of 603 pregnant women were included in this study, with 342 (56.7%) undergoing IOL at 40-40^+ 6 weeks and 261 (43.3%) at 41-41^+ 6 weeks. The primary pregnancy outcome was the rate of cesarean section (CS), and the secondary pregnancy outcomes included the rates of neonatal asphyxia and neonatal intensive care unit (NICU) admission. Maternal motivations regarding elective IOL were investigated.

Results: The rate of CS was 25.1% in the IOL at 40-40^+ 6 weeks group and 33.7% in the IOL at 41-41^+ 6 weeks group (p = 0.021). The three most prevalent indications for CS in both groups were: (1) non-reassuring fetal heart rate patterns (NRFHRP); (2) meconium-stained amniotic fluid; and (3) failed induction of labor. Compared with the 41-week IOL group, women who underwent IOL at 40 weeks' gestation exhibited higher educational attainment (93.6% vs. 82.0%, P < 0.001), a higher proportion of high-income families (91.5% vs. 68.2%, P < 0.001), a higher proportion of multiparae (24.0% vs. 16.5%, P < 0.05), a lower proportion of ripeness of the cervix (27.5% vs. 37.2%, P < 0.05), shorter hospitalization durations (5.84 ± 1.79 vs. 6.17 ± 1.95, P < 0.05), and higher hospitalization costs (13627.39 ± 3227.56 vs. 10837.77 ± 3276.73, P < 0.001). No significant intergroup differences were observed in the rates of neonatal asphyxia and NICU admission. The most common motivation for elective IOL was concern regarding fetal distress or stillbirth. Parity ≥ 1 and a Bishop score ≥ 6 were protective factors against CS following IOL.

Conclusions: IOL at 40 weeks did not result in increased adverse outcomes compared to IOL at 41 weeks. Parturients with higher education and income were more likely to choose elective IOL. Parity ≥ 1 and a Bishop score ≥ 6 were protective factors against CS following IOL. These may provide a new option for clinical decision-making.