Neonatal outcomes of hypertensive pregnancy subtypes in very preterm infants: a multicenter cohort study

To evaluate whether distinct subtypes of hypertensive disorders of pregnancy (HDP), chronic hypertension (CH), pregnancy-specific hypertensive disorders (PSHD), and superimposed preeclampsia (CH + PE), are associated with differential neonatal outcomes in very preterm infants, independent of gestational age and perinatal confounders.

We conducted a multicenter retrospective cohort study using prospectively collected data from the Brazilian Neonatal Research Network, including infants with birthweights 401-1500 g and gestational age 22 + 0 to 32 + 6 weeks (2013-2020). Infants were classified according to maternal hypertensive status. Primary outcomes included major neonatal morbidities and in-hospital mortality. Associations were assessed using Poisson regression with robust variance, adjusting for gestational age, birthweight, sex, antenatal corticosteroids, and perinatal variables. Analyses were stratified by gestational age (≤ 28 and > 28 weeks).

Among 9,689 infants, 4,011 (41.4%) were exposed to HDP. PSHD and CH + PE were associated with higher risks of respiratory distress syndrome and surfactant use across models. CH + PE was additionally associated with higher mortality, particularly in infants ≤ 28 weeks. In contrast, CH was associated with lower observed risks of late-onset sepsis and, among infants > 28 weeks, severe intraventricular hemorrhage. Several crude associations were attenuated after adjustment, highlighting the confounding effect of gestational age.

HDP subtypes were associated with distinct neonatal outcome profiles. PSHD and CH + PE were associated with higher risks of respiratory morbidity and mortality, whereas CH showed a more neutral profile and lower observed risks for selected outcomes. These findings support subtype-specific risk stratification in very preterm infants.