Nifedipine Versus Magnesium Sulfate for Treatment of Preterm Labor: Comparison of Efficacy and Adverse Effects in a Randomized Controlled Trial

Objectives: The study aimed to compare the efficacy and side effects of intravenous magnesium sulfate (MgSO4) and oral nifedipine for inhibition of preterm labor. Methods: This randomized controlled trial was performed on 220 women with preterm labor between 32 and 34 weeks of gestation who were randomly assigned to receive either MgSO4 or nifedipine. The primary outcome was inhibition of preterm labor, defined as prevention of delivery for 48 hours with inhibition of uterine contraction, and the secondary outcome was maternal side effects. Results: From 220 patients, 110 received nifedipine and 110 received MgSO4. There were no differences in suppression of labor pain in 24 hours and 48 hours between the two groups. Also, there were not statistically significant differences in one-minute and five-minute Apgar scores, neonatal respiratory distress syndrome, and NICU admission between the two groups. Maternal hypotension was higher in the nifedipine group, but the difference was not significant (P = 0.08). Dyspnea (P = 0.01) and minor maternal side effects (P ≤ 0.001) were significantly higher in the MgSO4 group than the nifedipine group. Serious maternal adverse effects and severe hypotension were not seen in any of the groups. Conclusions: Nifedipine is as effective as MgSO4 in arresting labor and delaying delivery for 48 hours. However, nifedipine is associated with significantly fewer maternal adverse effects.