Late preterm neonatal morbidity in hypertensive versus normotensive women

We estimated risks of late preterm (LP, 34°(/7)-36(6/7) weeks) delivery and neonatal respiratory and non-respiratory morbidity in women with mild and severe hypertension, in both low-risk and high-risk (history of chronic hypertension, preeclampsia (PE), or insulin-dependent diabetes in current pregnancy) cohorts.

This is a secondary analysis of two Maternal-Fetal Medicine Units Network randomized trials of aspirin to prevent PE. Women with non-anomalous singleton gestations delivered at ≥34 weeks were divided into three groups: normotensive, mild PE/gestational hypertension (GH), and severe PE/GH. Primary outcomes were respiratory (respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), or intubation) and non-respiratory (intraventricular hemorrhage, retinopathy of prematurity, small for gestational age (SGA) <10%, neonatal intensive care unit (NICU) admission, perinatal death, pulmonary hypertension, seizures, and 5 min Apgar <5) morbidity. Associations between LP delivery and risks of respiratory and non-respiratory morbidity were evaluated by fitting log-Binomial regression models before and after adjusting potential confounders.

Of 2781 women in the low-risk trial, mild and severe hypertension were diagnosed in 8.5% (n = 235) and 3.3% (n = 92), respectively. Respiratory morbidity was similar in all groups. Risks of non-respiratory morbidity were higher in the severe PE/GH group compared with normotensive women (28.3% vs. 16.8%, risk ratio 1.5, 95% confidence interval 1.1, 2.1). When restricting the analysis to late preterm infants, this risk was no longer present. Of the 1542 women in the high-risk trial, mild and severe hypertension were present in 16.6% (n = 256) and 11.9% (n = 184), respectively. Respiratory morbidity was again similar. Risks of non-respiratory morbidity were also not significantly increased in the high-risk cohort.

In both low- and high-risk women, mild PE/GH at ≥34 weeks is not associated with an increased risk of neonatal morbidity compared with normotensive women. Increased risk of composite neonatal morbidity related to severe PE/GH is confined to the subgroup of infants with non-respiratory morbidity, and disappears when including only late preterm infants.