July 10, 2002
The current standard of care for HIV-infected women is to treat them with the best possible regimen for their health, as long as there are no contraindications to using the agents. For pregnant women who would not start long-term treatment if they were not pregnant (based on their viral loads and CD4+ count), there is ample evidence, expert opinion, and growing consensus that HAART regimens during pregnancy are still the best choice. Many women would then consider stopping the regimen after delivery.
Constructing the best regimen means balancing effectiveness, resistance, maternal safety, and safety for the infant. The biggest problem remains our limited knowledge about the safety of different agents in pregnancy, and studies on attractive agents to use for pregnant women are rare.
That is why this case series on abacavir use in pregnancy is very important. A group from the Comprehensive Family AIDS Program in Fort Lauderdale, Florida reviewed all the patients they had treated with abacavir during pregnancy. They identified 36 treated women, almost all women of color. All but one were on abacavir with AZT and lamivudine, either as Combivir, Ziagen or as Trizivir. One woman was on d4T, lamivudine, and abacavir.
The bottom line is that the regimen was well tolerated, and appeared to be safe for mother and infant. Only one of the 36 women transmitted (less than 3 percent) HIV to her baby. However, the woman who did transmit HIV took little or none of her medication, had a climbing viral load and was hepatitis C co-infected. Viral loads were modest at baseline (mean 30,000, range less than 50 to 294,000). At delivery, when viral load is the best predictor of transmission, the mothers' viral loads were low with a median of less than 400 (meaning more than half were undetectable) but one woman remained at 129,000 copies. No episodes of hypersensitivity were reported; less than might be expected.
There was one premature birth, in a woman with late stage AIDS and bulimia. No illnesses or birth defects that might be suspicious for drug-related complications occurred. At six months, growth and development is normal, with the exception of one child who failed a hearing screen.
This is encouraging news, and provides some reassurance about the safety and efficacy of abacavir in pregnancy. Some cautions are necessary. First, it will take hundreds or thousands of exposed women to detect uncommon side effects or birth defects. Second, although the transmission rate is essentially 0 percent for women who took their medication, we don't know about pre-existing resistance or previous therapy. Third, there is some concern about abacavir, AZT and 3TC in patients with very high viral loads, and it is not clear whether those women with high viral loads treated with Trizivir or similar regimens might be more likely to transmit.
Still, this is good news. Nevirapine, AZT and 3TC are widely used in pregnancy and appear highly effective and safe, but some women will experience a rash, limiting the use of nevirapine. More worrisome, reports at this conference and elsewhere document a significant rate of NNRTI resistance in new patients. At Washington University in St. Louis, they reported 15 percent of a small group of pregnant women had NNRTI resistance at baseline. Single dose use, as is being done in many less developed countries until maternal treatment becomes available, will lead to NNRTI mutations in a large portion of women. In addition to abacavir, we desperately await more information on tenofovir in pregnancy.
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