Cordocentesis During Pregnancy
Cordocentesis is a diagnostic test that is sometimes done during pregnancy and is also called as umbilical vein sampling, fetal blood sampling, and percutaneous umbilical blood sampling. This diagnostic procedure involves obtaining a fetal blood sample through a needle inserted into the umbilical cord. The test is done by inserting a very fine needle into the mother’s abdomen up to one of the vessels of the cord. This test is done with the help of advanced imaging ultrasound when certain diagnostic information cannot be obtained by performing an amniocentesis.
The mother is given a sedative to slow fetal movements and facilitate extraction of sample. Cordocentesis test takes 45 minutes to 1 hour. The test is performed during the second trimester of pregnancy from week 17 or 18. This test is done when the gynecologist or neonatal radiologist suspects the baby to have a genetic or metabolic disease, fetal anemia or other hematologic disorders, a chromosome abnormality like Down’s syndrome, an infection such as rubella or toxoplasmosis, fetal malformations, or isoimmunization. Cordocentesis can also be done to treat the fetus administering certain medications or for doing a blood transfusion.
Cordocentesis carries some risk, so the gynecologist's indicates when the benefits of having an early diagnosis outweigh the risk to fetus. In approximately 2% of time, this test can cause miscarriage. The percentage of this risk varies greatly from one clinic or hospital to another depending on the professional experience of the person doing this test, as it involves high expertise and use of special technique.
The doctor removes 3 to 5 mm of blood, which is sent to pathology to be analyzed under microscope. The results are usually faster when cordocentesis is combined with amniocentesis, which can sometimes be important depending on the parent’s decision to continue or not with the pregnancy. Amniocentesis mentioned above is performed in cases of hydramnios or polyhydramnios (excess of amniotic fluid) or oligohydramnios (deficiency of amniotic fluid) described in detail in my previous articles.