Resistance to antiretrovirals in HIV-infected pregnant women.

Background: Antiretrovirals suppress HIV replication and prevent mother-to-child-transmission of HIV (PMTCT). Resistance to antiretrovirals may reduce the efficacy of PMTCT and/or complicate treatment of maternal or infant infection.

Objectives: To assess resistance to antiretrovirals during pregnancy.

Design: Retrospective chart review of 44 pregnancies.

Results: Twenty-two patients were antiretroviral treatment-naïve, 8 were on therapy, and 14 had prior therapy, but were off medication when the genotyping was performed. Major mutations were found in 10 antiretroviral-experienced women, including 5 women with major mutations to 2 classes of drugs (none to 3 classes). Major mutations were most common for lamivudine, nevirapine, zidovudine, stavudine, and abacavir. Three women had significant resistance to zidovudine/lamivudine, a combination recommended in PMTCT guidelines. Despite significant antiretroviral resistance, 6 of 8 women with plasma HIV RNA measured within 4 weeks of delivery achieved <50 copies/mL. All neonates were uninfected. Among 6 women who received antiretrovirals exclusively for PMTCT, there were no remarkable changes of the HIV genotype before and after pregnancy.

Conclusions: Resistance to antiretrovirals was common in antiretroviral-experienced pregnant women, but not in naïve women. The 14% prevalence of resistance to zidovudine and lamivudine in antiretroviral-experienced women suggests that alternative NRTI are desirable for this group of patients.