Magnesium sulfate and neonatal outcomes of preterm neonates

To determine whether in utero exposure to magnesium sulfate was associated with increased neonatal morbidity and mortality among premature neonates, and secondarily to determine the relationship, if any, between duration of magnesium sulfate exposure and neonatal morbidity and mortality.

We studied 401 neonates at our institution who were born between 23 and 34 weeks' gestation following preterm labor or preterm premature rupture of membranes. The population was stratified by exposure to magnesium sulfate and compared by various neonatal outcome variables. Similarly, the magnesium-exposed population was stratified by duration of exposure and compared for various neonatal outcome variables. Student's t test, chi2 test, Fisher's exact test and logistic regression were used for analysis.

A total of 190 neonates were exposed to magnesium sulfate, while 211 neonates were not. The magnesium-exposed neonates were delivered at a significantly lower gestational age compared to the unexposed neonates (28.2 +/- 3.0 vs. 29.3 +/- 3.1 weeks, p = 0.001). Univariate analysis revealed no differences between groups with regard to rates of respiratory distress syndrome, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis, patent ductus arteriosus, histological and clinical chorioamnionitis, neonatal sepsis or neonatal death. However, magnesium-exposed neonates were more likely to have received antibiotics (71.6% vs. 45.0%, p = 0.0001) and antenatal steroids (95.8% vs. 61.6%, p = 0.0001), factors known to affect perinatal morbidity and mortality. Controlling for antenatal confounding factors, magnesium sulfate use was not independently associated with neonatal mortality (odds ratio (OR) = 0.66; 95% confidence interval (CI) = 0.28, 1.54; p = 0.34). Seventy-nine neonates were exposed to magnesium sulfate therapy for more than 24 h, while 111 neonates were exposed for 24 h or less. There were no significant differences between groups with respect to neonatal outcomes, with the exception of an increased rate of clinical chorioamnionitis in the group exposed to magnesium for more than 24 h (22% vs. 8.2%, p = 0.005). After adjusting for gestational age at delivery, magnesium sulfate exposure for over 24 h was independently associated with a 2.8-fold increased rate of clinical chorioamnionitis (OR = 2.8, 95% CI = 1.14, 6.90; p = 0.02).

Prenatal exposure to magnesium sulfate was not associated with increased neonatal morbidity or mortality. However, prolonged exposure to magnesium sulfate may be associated with an increased risk of clinical chorioamnionitis.