['Undiagnosed HIV during pregnancy leads to increased perinatal infection. Four cases of adolescents/young adults with HIV contracted during pregnancy, after initial negative HIV testing, led to 4 cases of perinatal HIV, which were diagnosed only after AIDS-defining illness occurred in infants. These cases were missed despite HIV testing during pregnancy. This identifies a change in pattern for perinatal infection: increased adolescent/young adult HIV leading to increased perinatal risk.', 'A 10-year retrospective chart review on HIV-positive infants in an urban referral center. Charts were reviewed for timing of maternal HIV testing and reason for infant HIV diagnosis.', 'Twenty infected infants were referred over a 10-year period. Four HIV-infected infants were identified within a 2-year time frame at the end of the 10-year period. The 4 mothers were HIV negative, based on early peripartum testing (3 in first trimester and 1 in second trimester) and became infected or seroconverted during pregnancy after initial HIV test. The mothers diagnosed were all under the age of 25.'] Does increased adolescent HIV infection during pregnancy lead to increase in perinatal transmission at urban referral center?