Usefulness of atosiban for tocolysis during external cephalic version: Systematic review and meta-analysis

Introduction: Breech/transverse presentation is responsible for about 30-50 % of cesarean sections in the world. Cesarean section carries a five-fold greater morbidity than vaginal delivery, deeply impacting on women's health. External Cephalic Version (ECV) is an external manipulation used to convert a non-cephalic to a cephalic presentation. The use of tocolysis might facilitate this procedure; however, it is still controversial which drug should be considered as first choice.

Objective: To assess the effectiveness of tocolysis with atosiban, a competitive oxytocin receptor antagonist, in order to increase the rate of successful ECV.

Study design: Nine databases (including MEDLINE, CINAHL, LILACS, EMBASE, Scopus, ClinicalTrials.gov, Scielo, PROSPERO, Cochrane at CENTRAL) were searched from the inception to August 2020 using a combination of MeSH terms and keywords regarding "atosiban" and "external cephalic version". We included trials of women with a singleton pregnancy who reached at least 36 weeks of gestation and were scheduled to ECV and tocolysis with atosiban (intervention group) compared to beta-agonists or other drugs (control group). The primary outcome was the incidence of successful ECV. Summary measures were reported as relative risk (RR) with 95 % confidence interval (CI).

Data collection and analysis: Four studies (1534 women) were eligible for analysis. ECV success rate was significantly lower in women randomized to atosiban (36.7 % vs 45.3 %; RR 0.78 [95 % CI 0.6 to 0.98]). Cesarean section and vaginal delivery rates did not differ between intervention and control group ((59.8 % vs 52.6 %; RR 1.17 [0.98-1.38] and (38.6 % vs 45.0 %; RR 0.83 [95 % CI 0.69-1.01] respectively). Cephalic (36.9 % vs 44.6 %; RR 0.81 [95 % CI 0.65 to 1.01], or breech/transverse presentation at labor (63.4 % vs 55.1 %; RR 1.18 [95 % CI 0.99-1.40]), APGAR score less than 7 at 5 min (1.6 % vs 2.0 %; RR 1.14 [95 % CI 0.27-4.73], NICU admissions (44.2 % vs 48.1 %; RR 0.92 [95 % CI 0.58-1.46] and Umbilical cord pH were similar in both groups. Drug-related side effects were lower in women randomized to atosiban, compared with control group (16.0 % vs 42.9 %; RR 0.38 [95 % CI 0.31 to 0.47].

Conclusion: The use of atosiban for tocolysis does not improve the rate of successful ECVs when compared to beta-agonists. However, atosiban was associated with a significantly lower incidence of side effects and comparable cesarean section rates.