A cross-sectional study of pregnant women was conducted at Nsambya Hospital in Kampala, to investigate the prevalence and effect of Plasmodium falciparum infections during pregnancy, in a peri-urban/urban location. Overall, 544 pregnant women were recruited when they presented at the labour ward for delivery. After giving informed consent, each subject answered a questionnaire and underwent a physical examination, and peripheral-blood samples were obtained. After each uncomplicated delivery, samples of placental and cord blood were obtained from the placenta and infant, respectively, and infant birthweights were recorded. Smears were prepared from the blood samples and checked for parasites. Only 46 and 36 of the 537 women investigated were positive for P. falciparum infection in their peripheral and placental blood, respectively. Plasmodium falciparum was the only parasite encountered. The prevalences of low birthweight and maternal parasitaemia and the intensities of maternal infection were each greater in primigravidae than secundi- or multi-gravidae. Despite the low prevalence of parasitaemia in this population, P. falciparum infection in the primigravidae was a significant contributor to their ill health, leading to low birthweights in their infants.