Vaginal colonization with invasive Escherichia coli during pregnancy.

Escherichia coli containing the K1 antigen was isolated from women throughout their pregnancy and at delivery. The number of positive isolations varied from 5% to 7% throughout pregnancy, and 50% of the babies were coloinized if their mothers were positive for this organism at the time of delivery. In contrast to group B streptococci, the spontaneous loss or acquisition of E. coli K1 was uncommon.