By means of reflexion pulse oximetry the arterial oxygen saturation (SpO(2)) of 100 fetuses intrapartum was measured in a high-risk group and compared with clinical parameters. There is a connection between the duration of SpO(2) measurements below 30%, the delivery mode and reduced pH-values in the umbilical artery measured post partum. SpO(2) values below 30% also occur temporarily with uneventful deliveries but they occur with increased frequency within the group of operatively delivered children with a duration of more than 20 minutes. On the other hand the group with SpO(2) values ranging between 40 and 60% showed less operative deliveries and a better condition of the newborn (Apgar, pH-metry). If prognostically unfavourable additional criteria with variable decelerations increase, a tendency towards decreasing fetal oxygen saturation values is recognisable. In the case of suspicious heart rate patterns or patterns difficult to assess the continuous registration of saturation values is both medically and forensically of inestimable value. There were no increases in fetal morbidity or signs of amnion infection syndrome. By means of a new sensor; a longer registration lime with a reliable signal quality is achieved, so that assessment of the oxygen saturation in relation to labour activity becomes possible.