Comment: The quality of evidence is downgraded by study quality (often lack of allocation concealment and no blinding).
A Cochrane review included 14 studies with a total of 2 485 women.
Compared with placebo, atosiban (oxytocin receptor antagonist) did not reduce incidence of preterm birth (birth less than 48 hours after trial entry: average RR 1.05, 95% CI 0.15 to 7.43; random-effects, 2 studies, n=152) or improve neonatal outcome. However, the confidence intervals were wide. In one trial (583 infants), atosiban was associated with an increase in infant deaths at 12 months of age compared with placebo (relative risk (RR) 6.15; 95% confidence intervals (CI) 1.39 to 27.22). However, this trial randomised significantly more women to atosiban before 26 weeks' gestation. Use of atosiban resulted in lower infant birthweight (weighted mean difference –138.31 gm; 95% CI –248.76 to –27.86) and more maternal adverse drug reactions (RR 4.02; 95% CI 2.05 to 7.85, 2 trials, 613 women).
Comparing atosiban with nifedipine, no difference was shown in birth less than 48 hours after trial entry (average RR 1.09, 95% CI 0.44 to 2.73, random-effects; 2 studies, n=225). Atosiban resulted in less maternal adverse effects requiring cessation of treatment (RR 0.38, 95% CI 0.21 to 0.68; NNTB 6, 95% CI 5 to 12; 2 studies, n=225).
Comparing atosiban with betamimetics, no statistically significant difference was shown in birth less than 48 hours after trial entry (RR 0.89, 95% CI 0.66 to 1.22; 8 studies, n=1389) or perinatal mortality (RR 0.55, 95% CI 0.21 to 1.48; 3 studies, 816 infants), or major neonatal morbidity. Atosiban resulted in less maternal adverse effects requiring cessation of treatment (RR 0.05, 95% CI 0.02 to 0.11; NNTB 6, 95% CI 6 to 6; 5 studies, n=1161).
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