The management of preterm labour involves the acute suppression of uterine contractions. By inhibiting the end-organ response it is presumed the initial stimulus will not remain operative or the incident producing it has passed. It is a conveniently uninvestigated aspect of preterm labour research – so are randomized trials using placebo controls which are scarce and nifedipine has never been subjected to this gold-standard form of investigation (Caritis AJOG 2011;204:95-6).
Most trials of uterine activity suppression test one drug against another and look at relative efficacy and side-effects rather than neonatal outcomes. However in the present ethical climate it may be that comparative efficiency is the best that can be hoped for and the best evidence comes from a meta-analysis by Conde-Anudelo et al (AJOG 2011;204:134 e 1-20).
Their work shows nifedipine to be superior to beta-adrenergics and magnesium sulphate for tocolysis of women in preterm labour, so if a decision is made on clinical grounds to suppress the myometrium then there is guidance in favour of nifedipine for the person in charge of the case.
