In France, the rate of mother-to-child transmission of HIV-1 was 17% prior to 1994, when antiretroviral prophylaxis was not available. It fell to 1.6% [95% CI: 1.3–2.0] between 1997 and 2004, during the era of potent combination therapies, and reached 0.4% [0.1–0.9] when the viral load near delivery was less than 50 copies/mL. Three independent risk factors have been strongly linked to this “residual” transmission since 1997: gestational age at delivery (6 times higher risk for very preterm infants than for term infants), viral load at the end of pregnancy (a particularly significant increase above 10,000 copies/mL), and the duration of antiretroviral therapy during pregnancy (antepartum). For the 10% of women with virologic failure at delivery (>10,000 copies/mL), a delayed initial consultation in the maternity ward and the absence of intrapartum zidovudine infusion are associated with an increased risk of transmission. In the fortunately more common situation of women delivering at term with a well-controlled viral load (<400 copies/mL), the only factor significantly associated with the risk of transmission is the duration of antiretroviral therapy administered during pregnancy, with the rate decreasing linearly as this duration increases. (R.A.)