Proximity of magnesium exposure to delivery and neonatal outcomes

Am J Obstet Gynecol. 2016 Oct;215(4):508.e1-6. doi: 10.1016/j.ajog.2016.05.004. Epub 2016 May 10.


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

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

Study design: 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.

Results: 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.

Conclusion: 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.

Keywords: cerebral palsy; magnesium sulfate; neuroprotection; preterm delivery; time of last exposure.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Cerebral Palsy / prevention & control*
  • Delivery, Obstetric*
  • Female
  • Humans
  • Infant, Newborn
  • Magnesium Sulfate / therapeutic use*
  • Obstetric Labor, Premature
  • Odds Ratio
  • Placebos
  • Pregnancy
  • Premature Birth
  • Risk Factors
  • Time Factors


  • Placebos
  • Magnesium Sulfate