Nevirapine-based therapy is associated with increased frequency of adverse events among HIV-infected pregnant women. The aim of this article was to evaluate the incidence of adverse effects in HIV-infected women who started nevirapine during pregnancy. A retrospective study was performed in our center between January 2003 and December 2006 analyzing all women prescribed nevirapine during pregnancy. Women presenting any risk factor for hepatotoxicity were excluded from the analysis. Patients were divided into two groups according to the presence or absence of adverse effects, and a correlation to CD4 counts was performed. Liver function abnormality was graded according to the Division of AIDS toxicity guidelines. A total of 170 women initiated nevirapine during pregnancy, but only 133 were included in the study. Twenty-seven women (20.3%) presented adverse effects, skin rash accounting for 77.8% (21/27 women) and liver function abnormalities for 22.2% (6/27) of the cases. Baseline CD4 counts, viral loads and transaminases were similar in both groups. All nevirapine side effects were developed in less than seven weeks. Four of 31 women with CD4 counts <250 cells/μ μ μ μ μL (12.9%) and 23 of 102 women with CD4 counts ≥ ≥ ≥ ≥ ≥250 cells/μ μ μ μ μL (22.5%) developed adverse events. All patients who experienced hepatotoxicity had pretreatment CD4 counts ≥ ≥ ≥ ≥ ≥250cells/ μ μ μ μ μL. The incidence of adverse events with nevirapine in our study was high, but most of them were cutaneous. There was no correlation between high CD4 counts and adverse events when analyzing both cutaneous and hepatic reactions; nevertheless, hepatotoxicity occurred only in pregnant women with CD4 counts ≥ ≥ ≥ ≥ ≥250cells/μ μ μ μ μL.