A comparison of three tocolytics for preterm labor: A randomized clinical trial

Objective: To compare the efficacy and maternal side effects of nifedipine (N), magnesium sulfate (M), and indomethacin (I) for acute tocolysis. Methods: In this single center randomized trial, women in preterm labor 24-32 weeks' gestation received intravenous M, oral N, or I suppositories. The primary outcomes of interest were arrest of preterm labor (>48h, ≥7 days), gestational age at delivery, and maternal side effects. Results: Over a 38-month period, 301 women were allocated to receive M (90), N (114), or I (90). Gestational age at delivery (p=0.551) or arrest of labor >48h, >7 days were similar between the three groups (p=0.199, 0.654). Hypotension and tachycardia were more common in N patients compared to women receiving M or I (p=0.003, 0.009). Patients receiving I had more fetal ductal constriction or oligohydramnios compared to M or N (p=0.001, 0.020) but, I women were tested more often. There was one case of pulmonary edema in the M group and one with plural effusion in the N group. Conclusion: There were no differences in efficacy or in major maternal safety issues between the three tocolytic agents. Since there is no FDA approved tocolytic to treat preterm labor, clinicians should use the tocolytic that has afforded them the best results with the least maternal/neonatal side effects.