In a retrospective cohort analysis, loss to follow-up and mortality rates were compared between pregnant and nonpregnant women referred to a community-based antiretroviral treatment program in South Africa. Although there was no significant difference in adjusted mortality rates between the two groups, the pregnant women had a substantially higher risk of loss to follow-up both pretreatment and on-treatment. This finding highlights the need for programmatic interventions to address retention in care for this patient population.