The safety of tocolytics used for the inhibition of preterm labour

Preterm birth is the major cause of neonatal mortality and morbidity worldwide and a huge cost burden on healthcare. Between 22 and 26 completed weeks of gestation, for every day that delivery is delayed, survival increases by 3%.

Following a systematic review of the literature, we have provided an overview of the use of tocolytics for the prevention of preterm birth and have examined the fetal and maternal adverse effects of the various tocolytic agents currently in use.

No tocolytic currently in use was developed specifically to treat preterm labour so most have multi-organ side effects. β2-agonists are relatively safe for the fetus but have rare and potentially serious maternal adverse effects. In contrast, prostaglandin synthetase inhibitors have potentially serious side effects for the fetus and neonate but have mild maternal gastrointestinal side effects. In Europe, the choice of first line therapy is either atosiban or nifedipine. The evidence base for atosiban is much more robust than for nifedipine. While their efficacy is similar, atosiban has placebo level side effects and is safer than nifedipine but is much more expensive.