Magnesium Sulfate and PDA

Del Moral T, Gonzalez-Quintero VH, Claure N, et al. Antenatal exposure to magnesium sulfate and the incidence of patent ductus arteriosus in extremely low birth weight infants. J Perinatol (March 2007); 27: 154–157. Full Text | PDF

Objective: Magnesium sulfate (MgSO₄) is the most commonly used tocolytic agent in the US and is also employed as a prophylactic agent against seizures in pre-eclamptic women. MgSO₄ 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 MgSO₄ 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 MgSO₄ was compared with those not exposed and comparisons were also made between infants exposed to different maternal doses of MgSO₄.

Results: The incidence of PDA was significantly higher in the group of infants exposed to MgSO₄ 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

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 MgSO₄ (odds ratio 1.33 confidence interval (CI) 1.12 to 1.58, per 50 g of MgSO₄).

Conclusion: Antenatal exposure to MgSO₄ 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.

Comments: It appears that magnesium sulfate tocolysis is associated with a statistically-significant increased incidence of PDA in ELBW infants. Despite being of statistical significance, the difference between groups (67% vs. 60%) has minimal clinical significance. Of note: there was no difference between groups in the frequency of PDA that required surgical treatment. There was also no difference in mortality, severe IVH or PVL between groups. I doubt that these data will (or should) be sufficient to convince our obstetric colleagues to abandon the use of magnesium sulfate as a tocolytic. ABK.

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