Delayed appearance of Chlamydia trachomatis infections acquired at birth.

To determine the delay in detectability of Chlamydia trachomatis infections acquired at birth, we serially evaluated 120 infants born vaginally to infected women. Specimens for isolation of Chlamydia were taken from several anatomic sites. Results were analyzed for the age and site of the initial positive culture from each infant. Of 112 infants tested in the first month of life, 22% were culture-positive in the conjunctiva and 25% were positive in the pharynx. Initial positive rectal and vaginal cultures were obtained only in the third and fourth months of life, and all initial vaginal cultures were associated with positive rectal cultures. The latency of C. trachomatis in infants exposed at birth is often more than 1 month and can be longer than 97 days. This latency might be caused by suppression of the growth of the organism by antibodies acquired in utero.