Antenatal exposure to magnesium sulfate and the incidence of patent ductus arteriosus in extremely low birth weight infants.

OBJECTIVE: Magnesium sulfate (MgSO(4)) is the most commonly used tocolytic agent in the US and is also employed as a prophylactic agent against seizures in pre-eclamptic women. MgSO(4) crosses the placenta and its concentration in the newborn usually exceeds that of maternal levels. The purpose of this study was to explore the relationship between antenatal exposure to MgSO(4) and the incidence of patent ductus arteriosus (PDA) in extremely low birth weight infants. STUDY
DESIGN: A total of 954 neonates with birth weights between 500 and 1000 g, born at the University of Miami/Jackson Memorial Hospital between January 1995 and December 2004 and surviving for more than 3 days, were followed until death or discharge from the hospital. The incidence of PDA in infants exposed to MgSO(4) was compared with those not exposed and comparisons were also made between infants exposed to different maternal doses of MgSO(4).
RESULTS: The incidence of PDA was significantly higher in the group of infants exposed to MgSO(4) compared with the unexposed control group (67 vs. 60%, P<0.018). When stratified by gestational age the differences were significant only in the group of infants with a gestational age of >or=26 weeks (58 vs. 49%, P<0.039). Logistic regression analysis to adjust for co-variables indicated an increased risk of PDA with higher doses of MgSO(4) (odds ratio 1.33 confidence interval (CI) 1.12 to 1.58, per 50 g of MgSO(4)).
CONCLUSION: Antenatal exposure to MgSO(4) is associated with a higher risk of PDA in extremely low birth weight infants and this effect is more significant and dose-related in more mature infants.