The purpose of the Antiretroviral Pregnancy Registry (Registry) is to detect any major teratogenic effect involving any of the Registry drugs when administered to pregnant people. Registration is voluntary and confidential with information obtained from the health care provider. A Registry-assigned identifier allows for follow-up capability. Information on subjects is provided to the Registry prospectively (prior to the outcome of pregnancy being known) through their health care provider, with follow-up obtained from the health care provider after the outcome is determined. Providers are strongly urged to enroll their patients as early in pregnancy as possible to maximize the validity of the data. In addition, the Registry is very interested in assembling a group of providers who are willing to make a commitment to report all of their site's antiretroviral pregnancy exposures to the Registry, thereby assuring all cases can be considered prospective. Providers are encouraged to contact the Registry for more information about this group. The Registry is informed in its analysis by other data, for example, retrospective reports and clinical studies. Given the increasing number of medications and more aggressive approach to therapy, more HIV- and hepatitis B-infected people may be treated during pregnancy or become pregnant while under treatment. The paucity of data on use and infant outcomes of antiretroviral therapies during pregnancy makes this Registry an essential component of the ongoing program of epidemiologic studies of the safety of these therapies. Each year the Registry has enrolled approximately 1300-1700 pregnant people in the US exposed to antiretroviral drugs. This number represents approximately 15% of the 8,700 HIV positive people who give birth to live infants annually in the US.