Proximity of magnesium exposure to delivery and neonatal outcomes

In infants delivered preterm, magnesium sulfate reduces cerebral palsy in survivors. The benefit of magnesium given remote from delivery is unclear.

Our objective was to evaluate the association of time from last exposure to magnesium with cerebral palsy.

This was a secondary analysis of a multicenter trial evaluating magnesium for neuroprotection. For this study, we included women with live, nonanomalous, singleton gestations who received magnesium. Pregnancies with missing information at the 2 year follow-up were excluded. Women were divided into 2 groups based on exposure timing: last infusion of magnesium <12 hours and last infusion of magnesium ≥12 hours prior to delivery. The primary outcome was cerebral palsy of any severity at 2 years of life. Secondary outcomes were moderate/severe cerebral palsy and moderate/severe cerebral palsy or death. A χ(2) test, Student t test, and Mann-Whitney U test were used for bivariate associations. We fit a multivariable logistic regression model to adjust for confounders.

A total of 906 infants were analyzed. Five hundred sixty-eight were last exposed to magnesium <12 hours prior to delivery and 338 were last exposed ≥12 hours. Cerebral palsy occurred in 28 offspring (3%), 2.3% of those last exposed <12 hours vs 4.4% last exposed ≥12 hours prior to delivery (P = .07). On adjusted analyses, last exposure to magnesium <12 hours prior to delivery was associated with a significant reduction in cerebral palsy compared with last exposure ≥12 hours (adjusted odds ratio, 0.41, 95% confidence interval, 0.18-0.91, P = .03). There was no difference in secondary outcomes.

Exposure to magnesium proximal to delivery (<12 hours) is associated with a reduced odds of cerebral palsy compared with more remote exposure. This highlights the importance of the timing of magnesium for neuroprotection for women at risk of preterm delivery.