Second Trimester: Cordocentesis (Percutaneous Umbilical Blood Cord Sampling, PUBS)
Percutaneous Umbilical Blood Sampling (PUBS) is a procedure that can be used to obtain a small sample of the fetus' blood. The blood can then be analyzed for certain abnormalities. This diagnostic test (also called cordocentesis, fetal blood sampling, or umbilical vein sampling) is used to detect chromosome abnormalities indicating Down syndrome and blood disorders such as anemia and certain infections. PUBS is used when amniocentesis, chorionic villus sampling, or ultrasound cannot provide the information being sought or when these tests yield inconclusive results. PUBS can also be used as a way to deliver therapy to the fetus.
Cordocentesis is performed in a manner similar to amniocentesis. A fine needle is inserted through the pregnant woman's abdomen into the vein of the umbilical cord. The procedure lasts about an hour and may be done between weeks 18 to 22 of the pregnancy.
Miscarriage occurs 1 to 2 times out of every 100 procedures. Other potential side effects include blood loss from the puncture site, infection, a drop in the fetus' heart rate, or premature rupture of the membranes.