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Fetal Blood Sampling
Percutaneous umbilical cord blood sampling (PUBS) allows doctors to sample fetal blood under ultrasound guidance. The test is usually performed after 18 weeks gestation. It provides a means for rapid and accurate genetic testing, analysis of blood disorders (e.g. anemia, hemophilia, alloimmune thrombocytopenia, identification of congenital infection), or early detection of metabolic diseases that might possibly not be detected by amniocentesis or chorionic villus sampling in certain cases. This procedure is also used to perform blood transfusion (e.g. Rh incompatibility) and to directly administer medication to the fetus. An example of the latter is the direct treatment of fetal supraventricular tachycardia that is refractory to more conventional maternal therapy.
The procedure itself is similar to an amniocentesis procedure and involves placement of a small needle into the uterus for a fetal blood sample from the umbilical cord. PUBS has been reported with a loss rate of approximately 1 percent to 2 percent. Potential risks include spontaneous miscarriage, infection, hemorrhage preterm labor and premature delivery.