Cordocentesis - also known as percutaneous umbilical blood sampling - is a highly specialized prenatal test in which a sample of the baby's blood is removed from the umbilical cord for testing.Cordocentesis can be used to detect certain blood conditions and infections. Cordocentesis can also be used to deliver blood transfusions and medication to a baby through the umbilical cord.Use of cordocentesis is decreasing, however, since newer forms of technology can sometimes provide the same information from tests that pose a smaller risk of miscarriage - such as amniocentesis or chorionic villus sampling.Cordocentesis might be offered when:The desired information can't be obtained any other wayResults from other prenatal tests are unclearTest results might have a significant impact on the immediate management of the pregnancy