Twenty-six trials were included in the review (n=2,179 women): 23 trials of acute tocolysis and three trials of maintenance tocolysis. The quality of the included cohorts was variable: 13 trials scored 6 or more (high quality), five trials scored 4 or 5 and eight trials scored less than 3.
Acute tocolysis: For the primary outcomes, compared with beta2-adrenergic-receptor agonists, nifedipine was associated with a statistically significant reduction in the risk of delivery within seven days of treatment (RR 0.82, 95% CI 0.70 to 0.97, NNT=12, I2=0%; 10 trials) and admission to neonatal intensive care unit (RR 0.77, 95% CI 0.62 to 0.93, NNT=12, I2=0%; nine trials). There was no difference in perinatal mortality, mental retardation at two years and risk of delivery within 48 hours of treatment. Secondary outcome results were presented in the review.
For the primary outcomes, compared with magnesium sulphate, nifedipine was associated with a significant reduction in severe maternal adverse events (RR 0.46, 95% CI 0.23 to 0.93; one trial) and admission to neonatal intensive care unit (RR 0.72, 95% CI 0.53 to 0.97; one trial). There was no significant difference in risk of delivery within 48 hours of treatment. Secondary outcome results were presented in the review.
Evidence for nifedipine versus atosiban (one trial) and for nitric oxide donors (one trial) did not show any statistically significant benefits on primary outcomes.
Maintenance tocolysis: Compared with placebo/no treatment, nifedipine did not have any statistically significant benefits on primary outcomes.
There was no evidence of publication bias in any of the analyses. Sensitivity analysis on the basis of quality did not alter the results substantially.