Ritodrine in the treatment of preterm labour: a meta-analysis

Background & objectives: Results on the effect of ritodrine in the treatment of preterm labour are different all over the world. Therefore, a concrete conclusion cannot be drawn from a single randomized control trial (RCT). In this study, we selected a large number of RCTs worldwide on the treatment of preterm labour comparing ritodrine and placebo or magnesium sulfate and by applying meta-analysis, evaluated the effect of ritodrine in the treatment of preterm labour.

Methods: We searched and identified 20 RCTs about ritodrine versus placebo, and ritodrine versus magnesium sulphate in the main medical data resources (MEDLINE, PubMed, CBMdisc, Cochrane Library and EMBASE) from January 1970 to December 2001 published in English and Chinese literature. We abstracted data about delay of gestation, gestational age at delivery, birth weight, severe neonatal respiratory system diseases, perinatal deaths, and administration to contraction-ceased interval, etc.

Results: The odds ratio (OR) of 1 day (d) delay in 10 RCTs on ritodrine in preterm labour versus placebo was 2.95 (95%CI 2.15, 4.04), and OR of 2d delay was 1.91 (95%CI 1.49, 2.45), both differences were statistically significant. There were no significant difference on the OR of birth > or =37 wk, birth weight > or =2500 g, severe respiratory morbidity and perinatal mortality. The OR of 2d delay of four RCTs from abroad on ritodrine versus magnesium sulphate was 1.56 (95%CI 0.62, 3.94), and OR of 7d delay was 1.45 (95%CI 0.80, 2.62), both without significant difference. But the combined estimated rate difference (CERD) of side effects interruption rate was 12 per cent with significant difference. There were six Chinese RCTs on ritodrine and magnesium sulphate. The OR of 1d delay was 3.95 (95%CI 1.98, 7.88), and OR of neonatal death was 0.45 (95%CI 0.22, 0.93), both with significant difference. The average administration to contractionceased interval were 2.5 and 6.3 h, respectively, with CERD being -4.2 h.

Interpretation & conclusion: In treating preterm labour, ritodrine can significantly prolong a short interval more quickly but with relatively more side effects than magnesium sulphate. Stratified RCTs for different gestational ages and different labour stages should be designed for further study.