Tocolysis and preterm labour

There is persisting controversy about tocolytic treatment for preterm labour. This review addresses this controversy by appraising the recent clinical literature.

Surveys of obstetricians indicate a high usage of tocolysis for preterm labour, but evidence that this treatment confers overall benefit is still lacking. Betamimetics are now, correctly, being abandoned in favour of nifedipine, which has superior tocolytic properties and better neonatal outcomes. There is no evidence of effectiveness for magnesium sulphate as a tocolytic. Atosiban is a newer agent, which appears to be effective in delaying preterm birth with a favourable maternal safety profile, but there are persisting concerns about the lack of impact on perinatal mortality and morbidity. Current research is addressing the COX-2 inhibitor, rofecoxib, which has theoretical advantages with respect to fetal safety.

For the relatively small proportion of women in otherwise uncomplicated preterm labour prior to 34 weeks' gestation, there appears to be a place for short-term tocolysis to gain time so that corticosteroids can be administered to enhance fetal lung maturation and, if necessary, to transfer the woman to a facility with a neonatal intensive care unit. Nifedipine is an effective and cheap tocolytic agent. Atosiban appears to also be effective, but it is expensive and not universally available. Betamimetics and magnesium sulphate should be abandoned as tocolytic agents. There is a need for further clinical trials to establish an unequivocal evidence base for tocolysis, which requires placebo-controlled trials, and for comparative trials to identify the agent with superior characteristics.