Among 469 women with a diagnosis of HIV in pregnancy, 74 (15.8%) presented with less than 200 CD4 cells per cubic millimeter. The only variable significantly associated with this occurrence was African origin (odds ratio: 2.22, 95% confidence intervals: 1.32 to 3.75, P = 0.003). Four women with low CD4 (5.6%), compared with none with higher CD4 counts, had severe AIDS-defining conditions (P < 0.001) during pregnancy or soon after delivery, and one transmitted HIV to the newborn. Early preterm delivery (<32 weeks) was significantly more frequent with low CD4 (6.2% vs. 1.4%, P = 0.015). An earlier access to HIV testing, particularly among immigrants of African origin, can prevent severe HIV-related morbidity.