Coitus and chorioamnionitis: a prospective study.

Amniotic fluid infections have been strongly associated with coitus during pregnancy. If the relationship is causal it may be possible to identify a time sequence between coitus, penetration of bacteria through the mucous plug in the cervix, the development of infection in the extraplacental membranes near the cervical os, spread of the infection to the amniotic fluid and complications of the infection. The present study looked for such a sequence in an analysis of 541 pregnancies. A peak frequency of chorioamnionitis limited to the extraplacental membranes was present when labor and delivery took place within two days of the last coitus. In the next two days the infection spread to the amniotic fluid as evidenced by a peak frequency of maternal neutrophils migrating through the placental plate toward the amniotic cavity. Premature delivery was 4 times more frequent when there had been recent coitus and an amniotic fluid infection was present than when either factor was absent (P less than 0.01). Spontaneous rupture of the fetal membranes before the onset of and the membranes were inflamed than when these factors were absent (P less than 0.01). This raises the possibility that orgasm further weakened or ruptured membranes that had already been weakened by infection.