Objective We compared maternal and foetal outcomes between termination gestational age at 40 0/7-40 6/7 and 41 0/7-41 6/7 weeks. Design Retrospective cohort, observational, single-centre study. Setting Jiangsu Province Hospital, China: January 2020-December 2020 Population 1569 low-risk pregnancies. Methods Maternal medical records and neonatal delivery data were analysed retrospectively. Main outcome measures Difference in adverse outcomes of mothers and babies between termination gestational age at 40 0/7-40 6/7 and 41 0/7-41 6/7 weeks. Results The study included 1569 pregnancies, with 1107 (70.6%) delivered at 40 0/7-40 6/7 weeks and 462 (29.4%) delivered at 41 0/7-41 6/7 weeks. Intrapartum caesarean section (8% versus 16%, P<0.001), meconium-stained amniotic fluid (13% versus 19%, P=0.004), episiotomy (41% versus 49%, P=0.011), and macrosomia (13% versus 18%, P=0.026) were significantly lower at 40 0/7-40 6/7 weeks. The premature rupture of membranes rate(22% versus 12%, P<0.001), spontaneous labour rate(54% versus 20%, P<0.001), vaginal delivery rate of artificial rupture of membrane induction (83% versus 71%, P=0.006) and balloon catheter combined with oxytocin induction (88% versus 79%, P=0.049) were significantly higher at 40 0/7-40 6/7 weeks. Conclusions Low-risk women who delivered at 40 0/7-40 6/7 weeks showed better outcomes in terms of the mother’s and baby’s health, such as decreased rates of intrapartum caesarean section, meconium-stained amniotic fluid, episiotomy, and macrosomia, compared with those who delivered at 41 0/7-41 6/7 weeks. Tweetable abstract Induction at 40 weeks will decrease adverse outcomes of mothers and babies.