A prospective, randomized trial of nifedipine vs. ritodrine in threatened preterm labor.

OBJECTIVES: To compare the tocolytic efficacy and maternal tolerance of nifedipine with ritodrine in the management of threatened preterm labor.

METHODS: Prospective randomized study of 52 singleton pregnancies with preterm labor between 26 and 34 week's gestation. The capacity to delay delivery 48 h, 7 days, until week 36 or until fetal weight reached 2500 g were the outcome variables assessed. Doppler ultrasound studies were performed on the fetal umbilical artery as control.

RESULTS: No significant differences were found in the delay of delivery, but significantly fewer maternal side-effects were found in the nifedipine group. Doppler ultrasound results were similar in both groups.

CONCLUSIONS: Nifedipine is a valid and well-tolerated alternative among the tocolytic drugs, and apparently does not significantly alter fetal vascular blood flow.