The above quote testifies to the complexity of preterm labour, a process that ultimately results in considerable neonatal morbidity and mortality. It is diYcult to quantify the incidence of spontaneous preterm labour, as many studies relating to preterm birth do not discriminate between spontaneous preterm labour and iatrogenic/therapeutic preterm delivery. The picture is further complicated as many studies report their results by birth weight rather than gestation. However, it has been estimated that the incidence of preterm delivery varies from 5% to 10% of all births in developed countries, and that spontaneous preterm labour in otherwise uncomplicated singleton pregnancies accounts for between one third and one half of all preterm deliveries. 2 3 In 1997, in England and Wales, 50.3% of all neonatal deaths were due to immaturity. 4 The costs of neonatal intensive care in the short term and the resources needed to support children with long term morbidity as a result of preterm birth are considerable. The underlying physiology and molecular biology of preterm labour is complex and not yet fully understood. A full discussion of the processes involved is outside the scope of this paper but is covered in a recent review article. 5 The causes are also diverse and multifactorial. Figure 11 summarises some of the factors that may contribute to preterm labour. This paper will concentrate on the prediction, prevention, and treatment of preterm labour, and discuss the ways in which antenatal interventions can optimise the outcome for the fetus.