Randomized controlled trial of magnesium sulfate in women at risk of preterm delivery-neonatal cardiovascular effects.

OBJECTIVE: Use of antenatal magnesium sulfate (MgSO(4)) may reduce cerebral palsy in infants born very preterm. Low systemic blood flow in the first day in very preterm infants has been associated with cerebral injury and adverse motor outcome. The aim was to determine the effect of MgSO(4) on systemic blood flow in preterm infants.

STUDY DESIGN: Randomized trial of MgSO(4) versus saline placebo given to mothers at risk of delivery before 30 weeks gestation. Echocardiographic monitoring performed at 3 to 5, 10 to 12 and 24 h.

RESULT: A total of 48 infants were exposed to MgSO(4) and 39 to placebo. Infants exposed to MgSO(4) were significantly more likely to receive volume expansion (42% versus 21%). Inotrope use did not differ significantly (40% versus 26%). There was no significant difference in mean lowest superior vena cava (SVC) flow or right ventricular output (RVO), or incidence of low SVC flow or RVO in the first 24 h. Infants exposed to MgSO(4) had a significantly higher heart rate and were more likely to have low SVC flow at 10 to 12 h but not other times.

CONCLUSION: Antenatal MgSO(4) produced no consistent cardiovascular effects in the infant in the first 24 h. There is no evidence from this study to suggest the mechanism by which antenatal MgSO(4) prevents cerebral palsy is through a cardiovascular effect in the newborn.