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Post-term pregnancy is an independent risk factor for neonatal morbidity even in low-risk singleton pregnancies
  1. Nehama Linder1,2,
  2. Liran Hiersch2,3,
  3. Elana Fridman1,
  4. Gil Klinger2,4,
  5. Daniel Lubin1,
  6. Franck Kouadio1,
  7. Nir Melamed3
  1. 1Department of Neonatology, The Helen Schneider Hospital for Women, Rabin Medical Center, Petah Tikva, Israel
  2. 2Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
  3. 3Departments of Obstetrics and Gynecology, The Helen Schneider Hospital for Women, Rabin Medical Center, Petah Tikva, Israel
  4. 4Neonatal Intensive Care Unit, Schneider Children's Medical Center of Israel, Petah Tikva, Israel
  1. Correspondence to Professor Nehama Linder, MD, Department of Neonatology, The Helen Schneider Hospital for Women, Rabin Medical Center, Petah Tikva 49100, Israel; nehama.linder{at}gmail.com

Abstract

Objective To determine the independent association of post-term pregnancy with neonatal outcome in low-risk newborns.

Design Retrospective cohort.

Setting Tertiary university-affiliated medical centre.

Patients All newborns of low-risk singleton pregnancies born at 39+0 to 44+0 weeks’ gestation over a 5-year period. Exclusion criteria: 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.

Interventions None.

Outcome measures 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).

Results 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.

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

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