Preterm labour: a pharmacological challenge.

Preterm labour is a major cause of perinatal mortality and morbidity, but its prevention is difficult because most of the available drugs lack uterine selectivity and have potentially serious side-effects for the mother or the foetus. In this article, Andrés López Bernal and colleagues discuss new evidence that shows pregnancy is associated with changes in G protein signalling and second messenger formation in human myometrium. During gestation uterine relaxation is favoured by a pronounced increase in G alpha s levels, thereby facilitating the effect of agonists that increase cAMP formation. The change in G alpha s is reversed in spontaneous labour enabling the uterus to become responsive to contractile agents. Although it is not established that these changes in G protein function are causally related to the spontaneous onset of labour, nevertheless they provide a novel viewpoint towards increased understanding of the cellular mechanisms of uterine contractility, which may result in better drugs for the management of preterm labour.