Frequently asked questions on tocolytics.

The majority of drugs that are used today for tocolysis have been developed for clinical conditions other than preterm labour. Obstetricians started to use these drugs as tocolytics because of their additional influence on uterine smooth muscle relaxation, accepting their cardiovascular (side) effects. Because the majority of these drugs are used off label, today's strict criteria to evaluate drugs for their predominant use in pregnancy have not been applied; therefore, we also lack sufficient peri- and neonatal follow up data for these drugs. This problem is compounded as our understanding of the regulation of myometrial smooth muscle contraction and relaxation is still incomplete.