Infection due to Chlamydia trachomatis in pregnancy and the newborn.

Bacteria in the genus Chlamydia comprise three species, C. trachomatis, C. psittaci and C. pneumoniae. C. trachomatis infection is common, varying in prevalence in women from 0% to 37%. In the United States, the prevalence rate is estimated currently to be about 5%. Pregnancy may predispose to an increased chance of infection with C. trachomatis, through physiological immunosuppression and/or cervical ectopy. Maternal antibodies to C. trachomatis provide limited, if any, protection for the newborn. C. trachomatis causes pelvic inflammatory disease--which can result in tubal infertility or ectopic pregnancy and postabortal or late postpartum endometritis. It may also cause chorioamnionitis and premature delivery of the fetus. The incidence of vertical transmission of chlamydiae from mother to baby varies; if the mother is untreated, 20-50% of the newborns will develop conjunctivitis and 10-20% will develop pneumonia. C. psittaci infection in pregnancy is rare, but can cause spontaneous abortion. Whether C. pneumoniae infection in pregnancy has any influence on the outcome has not been ascertained. C. trachomatis can be detected by one or more of several methods; enzyme immunoassays are the least sensitive, but the most widely used. Screening for C. trachomatis in pregnancy may be of benefit in areas of high prevalence, and is generally regarded as being cost-effective if the prevalence rate is more than 5%. Pregnant women are best treated with erythromycin, 250 mg four times daily for 7 days. This will prevent infection of the newborn in more than 90% of cases. The infected neonate should be treated with erythromycin, given systemically and also with topical tetracycline if conjunctivitis is present.