Withdrawal of a sample of fetal blood, either from the umbilical vein during the antenatal period (see cordocentesis) or from a vein in the presenting part (usually the fetal scalp) during labour. The latter procedure is used to detect hypoxia, by measuring the fetal pH and degree of acidosis. The normal pH of fetal blood is 7.35 (range 7.45–7.25). The lower the pH, the more likely is the fetus to be suffering from hypoxia and acidosis, indicating an urgent need to deliver the baby.
Subjects: Medicine and Health.