Use of tocolytics: what is the benefit of gaining even more time?

Abstract

Today's dogma states that tocolytics can be used to prolong pregnancy for just 48 hours, allowing corticosteroids to be administered and transportation of the mother to a tertiary care centre. Surveys have shown that up to 30% of practitioners use maintenance tocolysis. Theoretically, maintenance tocolysis should be able to improve neonatal outcome by avoiding preterm birth and allowing delivery in the community maternity hospital or even at home, minimising social difficulties created by long distances between the mother and/or her baby and the rest of the family. This should result in fewer neonatal intensive care unit admissions, less respiratory distress syndrome and fewer long-term neurological sequelae. Such an effect has never been proven, probably because we do not know which women benefit from treatment, which do not require treatment because they are not in labour and which babies would better be born because chorioamnionitis and other insults jeopardize intrauterine development. Most studies on long-term tocolysis have been performed with beta-agonists. No improvement has been shown. On the contrary, a trend towards fetal harm with an increased risk for periventricular leucomalacia exists. Results from studies of one tocolytic should not be generalised; one published study on maintenance therapy with atosiban showed prolonged uterine quiescence and prolonged gestation, but was too small to detect differences in neonatal outcome. In the future, we need larger studies, not only to detect whether long-term tocolysis with newer tocolytics (oral oxytocin antagonists, prostaglandin receptor blockers) results in better neonatal outcome, especially at the lower gestational ages but also to discover methods that allow us to identify those women who will benefit from treatment and those for whom prolongation of pregnancy may cause harm.