The feasibility and accuracy of long-term transabdominal fetal electrocardiogram (fECG) recordings throughout pregnancy were studied using a portable fECG monitor. Fifteen-hour recordings of fetal heart rate (FHR) were performed in 150 pregnant women at 20-40 weeks of gestation and 1-hour recordings were performed in 22 women in labour and compared with simultaneous scalp electrode recordings. When >or=60% of fECG signals was present, the recording was defined as good. Eighty-two percent (123/150) of antenatal recordings were of good quality. This percentage increased to 90.7 (136/150 recordings) when only the night part (11 p.m.-7 a.m.) was considered. Transabdominal measurement of FHR and its variability correlated well with scalp electrode recordings (r=0.99, P<0.01; r=0.79, P<0.01, respectively). We demonstrated the feasibility and accuracy of long-term transabdominal fECG monitoring.