Risk of neonatal morbidity in deliveries at 40 weeks of gestation and beyond

Objective To evaluate the risk of neonatal morbidity associated with continuing pregnancy past 40 weeks of gestation, while separating deliveries with spontaneous onset, deliveries induced for fetal and non-fetal reasons, and ongoing pregnancies within each week of gestation. Methods Cohort study of 21 063 women delivering between 40 and 42 weeks of gestation, Aarhus University Hospital, Denmark. Results We found the risk of neonatal admission to increase with increasing gestational age not only after spontaneous onset of labour but also after induction of labour. The highest risk of neonatal admission was found in newborns delivered after induction of labour for fetal reasons (12%, 14% and 18 % respectively at 40, 41 and 42 weeks of gestation) and the lowest risk was found in newborns delivered after spontaneous onset (7%, 8% and 10% respectively at 40, 41 and 42 weeks of gestation). Ongoing pregnancies were associated with a statistically insignificant increased risk of neonatal admission compared with delivery after induction of labour for non-fetal reasons at 41 weeks (OR = 1.1 CI;(0.8 to 1.5)) and 42 weeks of gestation (OR = 1.5 CI;(0.7 to 3.2)). Similar patterns were found for neonatal respiratory morbidity, sepsis, hypoglycaemia and meconium aspiration syndrome. Conclusion The risk of neonatal admission increased with increasing gestational age from 40 weeks and beyond for both deliveries with spontaneous onset, induced deliveries and on-going pregnancies. Continuation of pregnancy at 41 and 42 weeks of gestation was associated with a small, insignificant increase in the risk of neonatal admission when compared with inducing deliveries for non-fetal reasons.