Oral betamimetics for maintenance therapy after threatened preterm labour

Background Some women who have threatened to give birth prematurely, subsequently settle. They may then take oral tocolytic maintenance therapy to prevent preterm birth and to prolong gestation. Objectives To assess the effects of oral betamimetic maintenance therapy after threatened preterm labour for preventing preterm birth. Search strategy We searched the Cochrane Pregnancy and Childbirth Trials Register (June 2005) and MEDLINE (from 1966 to August 2003). Selection criteria Randomised controlled trials comparing oral betamimetic with alternative tocolytic therapy, placebo or no therapy, for maintenance following treatment of threatened preterm labour. Data collection and analysis Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies. Main results Eleven randomised controlled trials (RCTs) were included. No differences were seen for admission to the neonatal intensive care unit when betamimetics were compared with placebo (relative risk (RR) 1.29, 95% confidence interval (CI) 0.64 to 2.60; one RCT of terbutaline with 140 women) or with magnesium (RR 0.80, 95% CI 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks) showed no significant difference in four RCTs, two comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.08, 95% CI 0.88 to 1.32, 384 women). No differences between betamimetics and placebo, no treatment or other tocolytics were seen for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than the groups allocated to placebo, no treatment or another type of tocolytic. Authors' conclusions Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labour.