The review included 95 RCTs which evaluated 18 treatments across eight tocolytic classifications (10,096 in the network analysis; range 30 to 1,749 across treatment comparisons). Of the 95 RCTs, 89 addressed incomplete data, 82 were free from reporting bias, 50 used adequate allocation concealment, 49 used an adequate method for random number generation, 30 reported blinding patients or personnel, 32 reported blinding outcome assessors and 92 were free from other biases. The results reported in this abstract were those from the network meta-analysis.
Delaying outcome delivery by 48 hours (55 trials): All active treatments were superior to placebo; this benefit did not reach statistical significance for the nitrates and other classes. Prostaglandin inhibitors were suggested as having a greater beneficial effect than any other active class, with an 83% probability of being the best. The probability of being ranked in the top three most efficacious classes was 96% for prostaglandin inhibitors, 63% for magnesium sulphate, 57% for calcium channel blockers, 33% for beta-mimetics, 24% for nitrates, 14% for oxytocin receptor blockers, 13% for others and 0% for placebo. Heterogeneity was observed (Ι²>50%) for both beta mimetic and magnesium sulphate when compared to placebo.
Maternal tocolytic-related adverse events (58 trials): Placebo was ranked first, with a probability of 61%, and a 98% probability of being ranked in the top three drug classes. The closest active competitor for reducing all cause maternal side effects was prostaglandin inhibitors, with a probability of 79%, followed by oxytocin receptor blockers (70%).
Reducing neonatal mortality (40 trials): Calcium channel blockers appeared to be the best, but the probability of this was only 41%. Prostaglandin inhibitors had the next highest probability of being the best (28%). The probability of being ranked in the top three most efficacious classes was 85% for calcium channel blockers, 58% for beta-mimetics, 56% for oxytocin receptor blockers and 54% for prostaglandin. There was substantial uncertainty around which class was associated with the fewest neonatal deaths. Heterogeneity was observed (Ι²=78%) for beta mimetic compared to placebo.
Reducing neonatal respiratory distress syndrome (42 trials): There was no evidence of a difference between the classes, with no clear benefit of any active treatment over placebo.
The overlap between the available direct estimates and network meta-analysis estimates were considered substantial (results from both were reported in the paper). Results for a range of secondary outcomes were reported. Sensitivity analyses and meta-regression showed no impact on the finding for prostaglandin inhibitors.