Intra-amniotic bacterial colonization in premature labor.

Bacterial culturing was performed on amniotic fluid obtained by transabdominal amniocentesis from 33 patients with singleton pregnancies who were in idiopathic premature labor with intact membranes prior to the thirty-fifth week of gestation. Bacteria were isolated in seven patients (21.2%). The patients who were at highest risk for intra-amniotic colonization were those who had two or more clinical parameters suspicious for intra-amniotic infection in a pregnancy prior to the thirtieth week. Anaerobic bacteria were isolated from all seven patients. Only one patient had mixed aerotolerance isolates. Anaerobic that were classified as significant pathogens were isolated in four patients. Three patients had isolates that grew on primary plates, and the rest were recovered only from broth. The greatest impact of intra-amniotic bacterial colonization in premature labor with intact membranes on perinatal outcome is expressed in extreme prematurity and appears to be a function of the pathogenicity and concentration of the offending organism(s).