The association between persistent maternal hypotension and small for gestational age neonates

Abstract

The association between maternal hypotension and poor fetal growth has not been well studied. We hypothesized that the presence of persistent maternal hypotension will reflect a chronic reduction of uteroplacental blood flow, leading to placental hypoperfusion and subsequent poor fetal growth. We aimed to evaluate whether persistent hypotension is associated with the risk of having a small for gestational age neonate. A secondary aim was to evaluate whether transient hypotension is associated with the same risk of having a small for gestational age neonate. We performed a secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be data, a large prospective cohort study of nulliparous women. The inclusion criteria included delivery of subjects with singleton pregnancies at ≥24 weeks' gestation who had systolic and diastolic blood pressure data at 3 antenatal visits between 6 0/7 and 29 6/7 weeks' gestation. Univariable analyses were performed to evaluate the association among persistent hypotension (systolic blood pressure of <100 mm Hg and or diastolic blood pressure of <60 mm Hg at 3 antenatal visits), transient hypotension (systolic blood pressure <100 mm Hg and diastolic blood pressure <60 mm Hg at any 1 of 3 aforementioned visits but not all 3), maternal characteristics and small for gestational age neonates. Variables found to be significant (P<.05) were included in multivariable logistic regression. Here, 164 of 7233 participants (2.3%) had persistent hypotension. In univariable analyses, subjects with persistent hypotension compared with those without were significantly more likely to have small for gestational age neonates (21.3% vs 11.6%; P<.001). When adjusting for confounders, persistent hypotension remained significantly associated with an increased risk of having a small for gestational age neonate (adjusted odds ratio, 1.65; 95% confidence interval, 1.11-2.44). In multivariable analysis, transient hypotension was not associated with an increased risk of having a small for gestational age neonate. Persistent hypotension was significantly associated with small for gestational age among neonates born to low-risk nulliparous women.