Cordocentesis, also referred to as fetal blood sampling, is a test used to detect fetal abnormalities. It is done by examining blood from the fetus.
Cordocentesis is generally performed when diagnostic information can't be obtained through another procedure such as amniocentesis, CVS or ultrasound, or if results from these tests were inconclusive. Cordocentesis looks for specific abnormalities, such as chromosome abnormalities such as Down syndrome. It can also look for malformation of the fetus, fetal infection, fetal anemia and other concerns.
To perform a cordocentesis, an ultrasound image is first required to determine the exact location in which the umbilical cord inserts into the placenta. The ultrasound guides a thin needle through the abdomen and uterine walls to the umbilical cord. The needle is then inserted into the umbilical cord to retrieve a small sample of fetal blood. The procedure takes about an hour.
The sample is sent to the laboratory for analysis, and results are usually available within 72 hours.
There is a small risk of miscarriage with a cordocentesis, approximately 1-2%.