Objective: To compare the efficacy of tocolysis with specific regimens of nifedipine and ritodrine. Maternal side effects and neonatal outcome also were evaluated.
Design: A prospective, randomised trial.
Subjects: Seventy-one women, including 11 with twin pregnancies, who had uterine contractions and observed cervical changes.
Main outcome measures: Prolongation of pregnancy for 48 h, seven days and until 36 weeks of pregnancy were evaluated for each treatment. Maternal side effects and haemodynamic changes were compared, as well as neonatal outcomes.
Results: Delivery was delayed for 48 h, seven days, and until the 36th week of gestation in 83%, 67%, and 50%, respectively, of women in the nifedipine group, compared with 77%, 63% and 43%, respectively, of women in the ritodrine group (no significant difference). Maternal side effects were significantly less common in the ritodrine group (no significant difference). Maternal side effects were significantly less common in the nifedipine group (27%) than in the ritodrine group (77%) (P < 0.001). The neonatal outcome was similar in the two groups. The fall in mean arterial and diastolic blood pressure, and the rise in maternal heart rate were significantly greater in the women who received ritodrine compared with those treated with nifedipine.
Conclusions: Nifedipine is as effective as ritodrine in suppressing preterm labour. Its use is associated with less frequent side effects.