Prevalence of the T215Y Mutation in Human Immunodeficiency Virus Type 1-Infected Pregnant Women in a New York Cohort, 1995–1999

From 1997 through 1999, the prevalence of the zidovudine resistance mutation T215Y was 9.7% among pregnant women, and the human immunodeficiency virus type 1 (HIV-1) load in those with resistant virus was higher than that measured in women with wild-type HIV-1. All mutations were noted in women with zidovudine experience, which suggests that monotherapy may not be adequate prophylaxis for vertical transmission of HIV-1 infection in the current era.