OBJECTIVE: To describe factors associated with pregnancy and trends in pregnancy rates among women with human immunodeficiency virus (HIV) before and after the release of U.S. Public Health Service Guidelines for the Use of Zidovudine and the Increased Availability of Highly Active Antiretroviral Therapy. METHODS: Human immunodeficiency virus (HIV)-infected women aged 15 to 44 years who were enrolled in the Adult/Adolescent Spectrum of HIV Disease Project, a medical records cohort study of HIV-infected persons conducted in more than 100 U.S. health care facilities. RESULTS: Among 8,857 women, there were 1,185 incident pregnancies during 21,617 person-years of follow-up from 1992 through 2001. Pregnancy rate at enrollment was 16%; thereafter, an average of 5.5%of women became pregnant annually. Pregnancies were more likely to occur in women aged 15 to 24 years (adjusted rate ratio [RR] 9.2; 95%confidence interval [CI] 7.4, 11.3) and 25 to 34 years (adjusted RR 4.0; 95%CI 3.3, 4.9) than in women aged 35 to 44 years. Pregnancies were less likely to occur in women with a history of acquired immunodeficiency syndrome (AIDS) opportunistic illness (adjusted RR 0.4; 95%CI 0.3, 0.5) or a CD4 count below 200 cells/μL and no opportunistic illness (adjusted RR 0.6; 95%CI 0.5, 0.7) than in women with HIV but not AIDS. Higher rates of pregnancy were observed for women prescribed highly active antiretroviral therapy (adjusted RR 1.3; 95%CI 1.0, 1.6) than women prescribed other regimens of antiretroviral therapy. There were significantly higher rates of pregnancy during 1997 through 2001. CONCLUSION: The increase in pregnancy rates during the era of widespread use of highly active antiretroviral therapy illustrates the continued need for comprehensive prevention and treatment services. OBJECTIVE: To describe factors associated with pregnancy and trends in pregnancy rates among women with human immunodeficiency virus (HIV) before and after the release of US Public Health Service Guidelines for the Use of Zidovudine and the Increased Availability of Highly Active Antiretroviral Therapy. METHODS: Human immunodeficiency virus (HIV) -infected women aged 15 to 44 years who were enrolled in the Adult / Adolescent Spectrum of HIV Disease Project, a medical records cohort study of HIV-infected persons conducted in more than 100 US health care facilities. RESULTS: Among 8,857 women, there were 1,185 incident pregnancies during 21,617 person-years of follow-up from 1992 through 2001. Pregnancy rate at enrollment was 16%; thereafter, an average of 5.5% of women became pregnant pregnant. Pregnancies were more likely to occur in women aged 15 to 24 years (adjusted rate ratio [RR] 9.2; 95% confidence interval [CI] 7.4, 11.3) and 25 to 34 years in women aged 35 to 44 years. Pregnancies were less likely to occur in women with a history of acquired immunodeficiency syndrome (AIDS) opportunistic illness (adjusted RR 0.4; 95% CI 0.3, 0.5) or a CD4 count below 200 cells / μL and higher rates of pregnancy were observed for women prescribed highly active antiretroviral therapy (adjusted RR 1.3; 95% CI 1.0, 1.6) than in women with HIV but not AIDS women prescribed other regimens of antiretroviral therapy. There were significantly higher rates of pregnancy during 1997 through 2001. CONCLUSION: The increase in pregnancy rates during the era of widespread use of highly active antiretroviral therapy showed the continued need for for comprehensive prevention and treatment services.