Meconium-stained amniotic fluid and neonatal morbidity in nulliparous patients with prolonged pregnancy

Our objective was to study the strength of the association between meconium-stained amniotic fluid and severe morbidity among neonates of nulliparas with prolonged pregnancies.

This was a secondary analysis of the NOCETER randomized trial that took place between 2009 and 2012 in which 11 French maternity units included 1373 nulliparas at 41⁺⁰  weeks of gestation onwards with a single live fetus in cephalic presentation. This analysis excluded patients with a cesarean delivery before labor and those with bloody amniotic fluid or of unreported consistency. The principal end point was a composite criterion of severe neonatal morbidity (neonatal death, 5-minute Apgar <7, convulsions in the first 24 h, meconium aspiration syndrome, mechanical ventilation ≥24 h, or neonatal intensive care unit admission for 5 days or more). The neonatal outcomes of pregnancies with thin or thick meconium-stained amniotic fluid were compared with those with normal amniotic fluid. The association between the consistency of the amniotic fluid and neonatal morbidity was tested by univariate and then multivariate analysis adjusted for gestational age at birth, duration of labor, and country of birth.

This study included 1274 patients: 803 (63%) in the group with normal amniotic fluid, 196 (15.4%) in the thin amniotic fluid group, and 275 (21.6%) in the thick amniotic fluid group. The neonates of patients with thick amniotic fluid had higher rates of neonatal morbidity than those of patients with normal amniotic fluid (7.3% vs. 2.2%; p < 0.001; adjusted relative risk [aRR] 3.3, 95% confidence interval [CI] 1.7-6.3), but those of patients with thin amniotic fluid did not (3.1% vs. 2.2%; p = 0.50; aRR 1.0, 95% CI, 0.4-2.7).

Among nulliparas at 41⁺⁰  weeks onwards, only thick meconium-stained amniotic fluid is associated with a higher rate of severe neonatal morbidity.