The impact of placental malaria in African urban areas is poorly documented. We therefore conducted a study during the rainy season in Dakar, an area with low malaria transmission. Two groups of delivering women were enrolled according to the detection of PfHRP2 in placental blood. Ten percent of the women were positive for parasites in the placenta, and microscopic examination showed, respectively, 17%, 22%, and 44% of past, acute, and chronic infection. The mean birth weight decreased drastically with the infection of the placenta (2,684 +/- 67 versus 3,085 +/- 66 g for controls), particularly with chronic infection. Chronic infection was not linked with parasiteamia in maternal venous blood. Seventy-six percent of positive women were anemic (46% of the controls). Severe anemia was also associated with chronic infection. Long-lasting infections are the most deleterious to mother and infant and are most likely associated with drug resistance of parasites.