An increased fetal DNA concentration in maternal plasma has been observed in placental pathological conditions associated with hypertension and preeclampsia. To confirm these data, we performed real-time quantitative PCR on the SRY gene in a group of physiological and pathological male-bearing pregnancies. In 78 physiological pregnancies, fetal DNA concentration in maternal plasma was 20.7, 13.4, 23.6, and 74.8 genome-equivalents (g.e.)/mL during the first, second, and third trimesters and at term, respectively. In 10 preeclamptic women, fetal DNA concentration ranged from 59.3 to 615.2 g.e./mL (median: 332.9). In 7 women with preeclampsia and IUGR (intrauterine growth retardation), fetal DNA ranged from 96.5 to 859 g.e./mL (median: 146.8). In 4 women with IUGR and hypertension, fetal DNA ranged from 34 to 473.5 g.e./mL (median: 142.4). In 3 patients with IUGR, fetal DNA ranged from 168.6 to 519.7 g.e./mL (median: 308.1). In 2 patients with IUGR and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome, fetal DNA concentration ranged from 105 to 394.1 g.e./mL (median: 249.7). Four women who developed preeclampsia some weeks later showed fetal DNA levels within the physiological range. These data suggest that increased fetal DNA concentrations might represent a valuable marker of placental abnormalities and suggest that this rise may precede clinical manifestation of preeclampsia by only a few weeks.