Preterm pre-labour rupture of membranes (pPROM) is the spontaneous rupture of fetal membranes at least an hour prior to the onset of labour, in a viable fetus (>23 weeks), and before 37 completed weeks of gestation. It complicates 2–3% of all pregnancies, thus affecting some 14 000 pregnancies in the UK and 140 000 in the US each year. pPROM accounts for 30–40% of preterm births and is an independent risk factor for neonatal morbidity and mortality from prematurity, neonatal, sepsis and pulmonary hypoplasia. Infants born after prolonged periods of pPROM have an excess risk of long-term neurological deficits and pulmonary disease. Subclinical intrauterine infection is a major etiological factor in the pathogenesis of pPROM. Studies of transabdominal amniocentesis following pPROM show that the frequency of positive culture for infection of the amniotic fluid is 25–40%. The risk of a positive culture is inversely related to the gestational age at which pPROM occurred. Women with intrauterine infection have shorter latency than non-infected women, and infants born with sepsis have a four-fold increase in mortality compared to infants born without sepsis.