December 18, 2001
The full spectrum of adverse effects related to antiretroviral agents cannot be determined during pre-approval clinical trials. As a result, post-approval studies of drug toxicity are particularly important in order to identify unanticipated side effects, especially those that may be rare and therefore difficult to identify.
An area of special concern is the potential teratogenicity of antiviral agents, especially since 70-80% of infants born to HIV-positive mothers will not be infected, even in the absence of therapy. As a result, the safety of maternal treatment related to teratogencity is critical for informed decision making among pregnant women and their caregivers. In her presentation entitled "Assessing the teratogenic risk of antiretroviral drugs: Data from the antiretroviral pregnancy registry," Dr. P. M. Garcia related some reassuring information from this international effort.
The major objective of the registry is to detect what Dr. Garcia described as a "teratogenic signal, rate, or pattern" related to antiviral treatment. Participation in the registry is voluntary, and 88% of the enrollees are from the United States. It is supervised by a multidisciplinary advisory committee consisting of HIV specialists, pediatricians, and experts in birth defects, with funding from government and industry sources. While there is both a prospective and a retrospective component to the registry, the retrospective component carries a high risk of ascertainment bias. The bulk of today's presentation related to the prospective component. The primary analysis is the number of birth defects/live births; an additional analysis compares birth defect rates in children born to women taking antivirals during their first versus their second and third trimesters.
The registry began in 1989, and has received 2,851 prospective reports. The average age of the mothers is 27 years, and the CD4 cell counts are mainly between 200 and 499. The overall rate of birth defects has been 2.4%, a rate comparable to that observed in the infants born to HIV-negative women. There has been no evidence of increased rates related to the time of in utero exposure, and enough data have been collected on AZT and 3TC to conclude that there is no apparent increased teratogenicity related to these medications.
One limitation of the registry is that it is designed only to capture major abnormalities, specifically those that would be diagnosed at the time of birth. For more subtle abnormalities or problems that would develop many years after birth, further close follow-up of both HIV-positive and HIV-negative children is essential. Nonetheless, the data presented are reassuring, and add another optimistic note to this major public health triumph in HIV prevention. Clinicians caring for HIV-positive pregnant women are encouraged to enroll them in the registry by calling 800-258-4263.
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