What are the realistic expectations of tocolytics?


Correspondence: Dr G. Smith, Division of Maternal–Fetal Medicine, Departments of Obstetrics and Gynaecology, Pharmacology and Toxicology, Anatomy and Cell Biology, and Imaging Services, Queen's University, 76 Stuart Street, Kingston, ON, Canada K7L 2V7.


Preterm birth, the leading cause of neonatal morbidity and mortality worldwide, is a major public health problem in terms of loss of life, long term disability (e.g. cerebral palsy, chronic lung disease), and health-care costs. The outcome of preterm infants is directly related to the gestational age at delivery. The goal of tocolytic therapy is to reduce neonatal morbidity and mortality by delaying delivery, to allow for the administration of corticosteroids and/or the safe transfer to a tertiary-care centre. However, currently available tocolytics in Canada (ritodrine, indomethacin, calcium antagonists, magnesium sulphate) have poor efficacy, have not been shown to increase the completion of a course of corticosteroids, are potentially associated with significant maternal/fetal side effects, and most importantly, have not been shown to improve neonatal outcomes. At the Canadian Tocolysis Consensus Conference, there was general agreement that recommendations should be based on good quality research evidence, particularly that of randomised clinical trials when available. It was concluded that there is little evidence to support the use of any of the currently available tocolytics; tocolytic use has not been associated with improved perinatal outcomes and often have detrimental effects on the mother. Therefore, questionable efficacy and potentially serious side effects may outweigh their use. Any new tocolytic demonstrated to improve neonatal outcome will have an immediate impact on societal and long term public health-care costs.