If there is concern that the fetus may have an viral or parasitic infection transmitted from the mother during pregnancy, such as Toxoplasmosis or cytomegalovirus.
If there is incompatibility between the fetus and maternal blood, cordocentesis can be used to determine a fetal blood type and blood count.
Cordocentesis may also be used to evaluate certain ultrasound abnormalities, such as if the baby appears to be in heart failure.
Evaluation of certain types of genetic abnormalities may require cordocentesis.
How is cordocentesis performed? Ultrasound is used to find the spot where the umbilical cord attaches to the placenta. Ultrasound is then used to guide a thin needle into the vein where the cord attaches to the placenta. When the needle enters the vein, 1 or 2 cc of fetal blood is then withdrawn (the amount depends on the reason for the test), and the needle is then withdrawn. The blood is then sent for the specific tests required.
When is cordocentesis performed? The timing of the procedure generally depends on the reason for which the procedure is being performed, but it can usually not be performed prior to about 18 weeks gestation because of the small size of the blood vessels.
What are the risks of cordocentesis? By definition, pregnancies in which a cordocentesis is performed are already at high risk. The additional risks and complications such as miscarriage due to the procedure itself are estimated at about 1% to 2%. This is higher than for amniocentesis, and could be due to additional problems, not present in amniocentesis, such as blood loss from the needle insertion site, or change in the baby’s heartbeat after the test.
Who is a candidate for cordocentesis? As mentioned above, cordocentesis is a highly specialized procedure that is generally performed only by a perinatologist on patients whose pregnancies are at high risk for very specific problems such as fetal infection or blood group incompatibility. If a problem arises in your pregnancy in which the perinatologist feels that a cordocentesis may be necessary, there will be a long discussion prior to the procedure to review the reason for the procedure, the risks of the procedure, what treatments can be offered in cases of abnormal results, etc.
