Risk of Neonatal Neurologic Morbidity in Advancing Term Gestations

Placental insufficiency is associated with neonatal neurologic morbidity and late-term gestations (41^0/7-41^6/7 weeks). Whether late-term infants are at increased risk of neurologic morbidity compared with term infants (39^0/7-40^6/7 weeks) remains unclear. We aim to compare risk of neurologic morbidity among late-term and term infants.

This secondary analysis of a single-institution prospective cohort study included all liveborn, nonanomalous singleton term and late-term infants, with data on adverse neonatal outcomes up until 28 days of life. The primary outcome was a neonatal neurologic morbidity composite, defined by having one of these conditions: neonatal seizures, intraventricular hemorrhage, hypoxic-ischemic encephalopathy, and neonatal hypothermic therapy. Secondary outcomes were the composite's individual components and nonneurologic neonatal morbidity. Multivariable logistic regression adjusted for delivery mode, nulliparity, and labor type.

Of 5,529 infants included, 747 were late term and 4,782 were term. The risk of composite neurologic morbidity was not significantly different among late-term or term infants (0.5 vs. 0.6%; adjusted odds ratio: 0.59, 95% confidence interval: 0.21-1.71). Overall neonatal morbidity was not significantly different in the two groups, though late-term infants had a nonsignificantly higher prevalence of respiratory distress syndrome (5.5 vs. 3.3%) and meconium aspiration syndrome (0.7 vs. 0.2%).

Neonatal neurologic morbidity is uncommon after 39 weeks. Risk does not increase after 41 weeks.