Maximum possible impact of tocolytics in preventing preterm birth: a retrospective assessment.

Although tocolytic drugs are widely used to try to stop preterm labor, their actual contribution to preventing preterm deliveries is unknown. Since tocolytic drugs are not used at the University of Manitoba, it was possible to estimate the proportion of preterm deliveries that might have been eligible for tocolytic drug therapy. Of 364 consecutive preterm deliveries between 24 and 35 weeks, only 9% would have been eligible for, let alone prevented by, tocolytic drug therapy, and even a smaller percentage of babies would actually have benefitted from their use. The use of tocolytic drugs can, at best, benefit only a very small percentage of babies born preterm. Whether the risks of treatment justify this small benefit is arguable.