Background

Preterm birth is a major contributor to perinatal mortality and morbidity worldwide. Tocolytic agents are drugs used to inhibit uterine contractions. The most widely used tocolytic agents are betamimetics especially in resource‐poor countries.

Objectives

To assess the effects of betamimetics given to women with preterm labour.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2006) without language restrictions. We updated this search on 1 October 2009 and added the results to the awaiting classification section.

Selection criteria

Randomised controlled trials of betamimetics, administered by any route or any dose, in the treatment of women in preterm labour where betamimetics are compared with other betamimetics, placebo or no treatment.

Data collection and analysis

Two review authors evaluated independently methodological quality and extracted the data. We sought additional information to enable assessment of methodology and conduct intention‐to‐treat analyses. We present the results using the relative risk for categorical data and the weighted mean difference for continuous data.

Main results

Seventeen randomised controlled trials are included. Eleven trials, involving 1320 women, compared betamimetics with placebo. Betamimetics decreased the number of women in preterm labour giving birth within 48 hours (relative risk (RR) 0.63; 95% confidence interval (CI) 0.53 to 0.75) but there was no decrease in the number of births within seven days after carrying out a sensitivity analysis of studies with adequate allocation of concealment. No benefit was demonstrated for betamimetics on perinatal death (RR 0.84; 95% CI 0.46 to 1.55, seven trials, n = 1332), or neonatal death (RR 1.00; 95% CI 0.48 to 2.09, five trials, n = 1174). No significant effect was demonstrated for respiratory distress syndrome (RR 0.87; 95% CI 0.71 to 1.08, eight trials, n = 1239). A few trials reported the following outcomes, with no difference detected: cerebral palsy, infant death and necrotizing enterocolitis. Betamimetics were significantly associated with the following: withdrawal from treatment due to adverse effects; chest pain; dyspnea; tachycardia; palpitation; tremor; headaches; hypokalemia; hyperglycemia; nausea or vomiting; and nasal stuffiness; and fetal tachycardia. Other betamimetics were compared with ritodrine in five trials (n = 948) and hexoprenaline compared with salbutamol in one trial (n = 140). Trials were small, varied and of insufficient quality to delineate any consistent patterns of effect.

Authors' conclusions

Betamimetics help to delay delivery for women transferred to tertiary care or completed a course of antenatal corticosteroids. However, multiple adverse effects must be considered. The data are too few to support the use of any particular betamimetics.

[Note: The 14 citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]