Pure fetal blood has been aspirated in utero from the umbilical vein near the placental insertion of the cord using a twenty gauge needle under ultrasound guidance. Sixty-six samples were taken on 63 pregnancies between 17 and 32 weeks of gestation. One to two millilitres of blood can be obtained easily without amniotic fluid dilution or contamination by maternal blood, as confirmed by the measurements of the mean corpuscular volume, the histogram distribution of the red blood cells and the hematocrit. In all cases the Kleihauer test and isoelectrofocusing of the hemoglobins were performed. Coagulation factors were also studied in 60 cases. In 17 cases a medical abortion was voluntarily induced after the procedure, and the follow-up was normal during the observation period after sampling. In the other cases, pregnancies have continued normally and twelve healthy babies have already been born.