Magnesium sulfate exposure and neonatal intensive care unit admission at term

The aim of this study was to investigate the effect of maternal magnesium sulfate (MgSO4) exposure for eclampsia prophylaxis on neonatal intensive care unit (NICU) admission rates for term newborns.

A secondary analysis of the Maternal-Fetal Medicine Unit Network Cesarean Registry, including primary and repeat cesarean deliveries, and failed and successful trials of labor after cesarean was conducted. Singleton pregnancies among women with preeclampsia and >37 weeks of gestation were included. Pregnancies with uterine rupture, chorioamnionitis and congenital malformations were excluded. Logistic regression analysis was used to determine associations between MgSO4 exposure and NICU admission. P<0.05 was considered statistically significant.

Two thousand one hundred and sixty-six term pregnancies of women with preeclampsia were included, of whom 1747 (81%) received MgSO4 for eclampsia prophylaxis and 419 (19%) did not. NICU admission rates were higher among newborns exposed to MgSO4 vs unexposed (22% vs 12%, P<0.001). After controlling for neonatal birth weight, gestational age and maternal demographic and obstetric factors, NICU admission remained significantly associated with antenatal MgSO4 exposure (adjusted odds ratio 1.9, 95% confidence interval 1.3 to 2.6, P<0.001). Newborns exposed to MgSO4 were more likely to have Apgar scores <7 at 1 and 5 min (15% vs 11% unexposed, P=0.01 and 3% vs 0.7% unexposed, P=0.008). There were no significant differences in NICU length of stay (median 5 (range 2 to 91) vs 6 (3 to 15), P=0.5).

Antenatal maternal MgSO4 treatment was associated with increased NICU admission rates among exposed term newborns of mothers with preeclampsia. This study highlights the need for studies of maternal MgSO4 administration protocols that optimize maternal and fetal benefits and minimize risks.