An update on the controversies of tocolytic therapy for the prevention of preterm birth

Preterm birth is the major cause of perinatal mortality and morbidity in the developed world. Where there are no contraindications to their use, tocolytics can improve neonatal survival rates by approximately 3% per day between 23 and 27 weeks gestation with a concomitant reduction in morbidity. The ultimate aim of tocolytic therapy is to prolong pregnancy until growth and maturation is complete, but even short-term delay may enable the administration of antepartum glucocorticoids to reduce hyaline membrane disease or to arrange transfer to a center with neonatal intensive care facilities. Both of these have been shown to reduce neonatal mortality and morbidity. Until recently, none of the currently used tocolytics, whether licensed or unlicensed, were developed specifically for the inhibition of preterm labor and consequently, they exhibit various potentially serious side-effects. As a result of the recent licensing of the oxytocin antagonist, atosiban, developed for the treatment of preterm labor and due to its high utero-specificity, obstetricians have experienced an advance in their options for the management of spontaneous preterm labor.