Post-term pregnancy is an independent risk factor for neonatal morbidity even in low-risk singleton pregnancies

TLDR

The study aimed to assess whether post‑term delivery independently increases neonatal morbidity in low‑risk singleton pregnancies. A retrospective cohort of 23,524 low‑risk singleton births (39–44 weeks) at a tertiary center was analyzed, comparing post‑term, late‑term, and full‑term infants for neonatal outcomes. Post‑term infants had twice the odds of NICU admission, higher rates of respiratory and infectious morbidity, and increased caesarean and operative vaginal deliveries compared to late‑term and full‑term infants, with no increase in neonatal mortality.

Abstract

To determine the independent association of post-term pregnancy with neonatal outcome in low-risk newborns.Retrospective cohort.Tertiary university-affiliated medical centre.All newborns of low-risk singleton pregnancies born at 39+0 to 44+0 weeks' gestation over a 5-year period.multiple gestation, maternal hypertensive disorder, diabetes or cholestasis, placental abruption or intrapartum fever (>38°C), small for gestational age (<10th centile) and major congenital or chromosomal anomalies.None.Admission to the neonatal intensive care unit (NICU), hospital length of stay, 5-min Apgar score, birth trauma, respiratory, neurological, metabolic and infectious morbidities and neonatal mortality. The adverse outcome rate was compared among three groups based on gestational age at birth: post-term (≥42+0 weeks), late term (41+0 to 41+6 weeks) and full term (39+0 to 40+6 weeks).Of the 23 524 eligible neonates, 747 (3.2%) were born post-term, 4632 (19.7%) late term and 18 145 (77.1%) full term. Women in the post-term group versus the late-term group had a significantly higher rate of caesarean section (8.9% vs 5.6%, p<0.001) and operative vaginal delivery (9.6% vs 7.4%, p=0.024). Post-term pregnancy versus full-term pregnancy was associated with an increased risk of NICU admission (OR 2.0, 95% CI 1.4 to 2.8), respiratory morbidity (OR 2.2, 95% CI 1.3 to 3.8) and infectious morbidity (OR 1.88, 95% CI 1.32 to 2.69). Post-term pregnancy versus late-term pregnancy was similarly associated with an increased risk of NICU admission (OR 2.0, 95% CI 1.4 to 2.9), respiratory morbidity (OR 2.7, 95% CI 1.5 to 5.0) and infectious morbidity (OR 1.8, 95% CI 1.2 to 2.7) and with hypoglycaemia (OR 2.6, 95% CI 1.2 to 5.4). Post-term delivery was not associated with neonatal mortality.Post-term pregnancy is an independent risk factor for neonatal morbidity even in low-risk singleton pregnancies.