Causes and consequences of premature rupture of fetal membranes.

Data from 6613 pregnancies that ended before term were analysed to determine whether amniotic-fluid infections are a cause as well as a consequence of premature rupture of the fetal membranes. Amniotic-fluid infections seem to be a cause of such ruptures because the infections were 2-3 fold more common when the fetal membranes ruptured just before labour started than when they ruptured just after the onset of labour. There was no relation between the frequency of premature rupture and the number of coital acts in the month before delivery but at every gestational age the proportion of fetuses and neonates who died with amniotic-fluid infections was greater when coitus had occurred in the month before delivery. This was because the infections associated with coitus were more severe. Low Apgar scores and neonatal hyperbilirubinaemia were 60% more frequent when preterm delivery was due to premature rupture of the membranes than when it was due to other causes. This was mainly the result of the high frequency of amniotic-fluid infections associated with the premature membrane ruptures.