Intravenous magnesium sulfate for premature labor: comparison between twin and singleton gestations

Premature labor occurs frequently in twin gestations, and intravenous magnesium sulfate is commonly prescribed for tocolysis. The purpose of the present investigation was to determine the efficacy and safety of intravenous magnesium sulfate tocolysis in twin gestations using dosing regimens reported for singletons. Outcomes were compared between cases of singleton gestations eligible for tocolysis and admitted immediately before and after each twin case. The standard loading dose in both groups was 4 to 6 g intravenously with a maintenance dose of 1 to 3 g/hr. Data were compared using unpaired t tests or chi-square analysis where appropriate. The 24 evaluable cases of twins were similar in demographics to a similar cohort of 48 singletons. Frequencies of side effects and durations of therapy were the same between the two groups. The number of days from beginning therapy until delivery was highly variable but not significantly different for the twin and singleton groups (13.5 +/- 14.8 vs 20.9 +/- 20.1 days, mean +/- SD). No significant differences were found between the twin and singleton groups in delays in delivery during the first 72 hours (16 [66.7%] vs 35 [72.9%]) and by the 33rd completed week (10 [41.6%] vs 25 [52.1%]). In conclusion, guidelines for prescribing intravenous magnesium sulfate to inhibit premature labor in singletons are equally safe and effective for twin gestations.