Fetal Blood Sampling and Transfusion

Fetal blood sampling or cordocentesis is a straightforward procedure where fetal blood is typically accessed at the site of the umbilical vein, using a long, small‐gauge spinal needle. Access to fetal blood via the hepatic vein or heart (cardiocentesis) has also been described. Most of the time cordocentesis is performed as the precursor to fetal transfusion. Cytogenetic analysis via fetal blood sampling is usually reserved for cases where quick turnaround of results is required, such as when a patient is nearing the gestational age for legal termination of pregnancy or when the results might affect delivery planning and neonatal management of a fetus with an anatomical abnormality. Cordocentesis is rarely used to evaluate or treat a fetus with congenital infection. The one exception to this rule would be the evaluation and treatment of fetal parvovirus B19 infection, which causes fetal anemia via bone marrow failure.