A procedure performed during a mother's labour in which a blood sample is taken from a vein in the scalp of the FETUS. This enables tests to be performed that indicate whether the fetus is, for example, suffering from a shortage of oxygen (HYPOXIA). If so, the obstetrician will usually accelerate the baby's birth. The term is also used in reference to testing fetal cells present in the pregnant mother's blood for their DNA composition.