An assessment of key aetiological factors associated with preterm birth and perinatal mortality.

The 4 main causes of preterm births in 303 women with consecutive deliveries in Flinders Medical Centre were premature rupture of the membranes (39%), spontaneous preterm labour (22%), pregnancy-induced hypertension (17%) and antepartum haemorrhage (12%). Premature rupture of the membranes occurred with equal frequency in singleton and multiple pregnancies and there was no difference in the frequency of this cause between the pregnancies with live outcomes and those with perinatal deaths. Spontaneous preterm labour was more common in multiple pregnancies (39%) than in singleton pregnancies (22%). One in 3 of the preterm births and 79% of the pregnancies with perinatal deaths occurred at less than 32 weeks' gestation. As it is unlikely that any single obstetric and social intervention will be able to reduce these causes of preterm birth research must continue to find markers to predict premature rupture of the membranes and spontaneous preterm labour.