Fetal Blood Sampling (Cordocentesis)
What is fetal blood sampling?
Fetal blood sampling involves the removal a small amount of blood from the umbilical cord. The cord blood contains fetal blood cells which are used to analyze the chromosomes of the baby.
How is fetal blood sampling done?
If technically possible, a thin needle is passed through the maternal abdomen into umbilical cord at the cord insertion site into the placenta (afterbirth). A small amount of fetal blood is removed from the cord (2.5mL or half a teaspoon of blood). The procedure is performed under ultrasound guidance and the needle can be visualized at all times. The procedure lasts less than 1-2 minutes and afterwards we check that the fetal heart beat is normal. The test is usually performed between 20 and 23 weeks gestational age.
For the first couple of days you may experience some abdominal discomfort, period-like pain or a little bleeding. These are relatively common and in the vast majority of cases the pregnancy continues without any problems. You may find it helpful to take simple painkillers like paracetamol 40 minutes before the procedure. If there is a lot of pain or bleeding or if you develop a temperature please seek medical advice.
When can I expect to get the results?
Rapid determination of fetal chromosomes can be obtained on the fetal red blood cells. The results for Down’s syndrome and all other major chromosomal defects are usually available within 5 working days (full culture).
Will the procedure need to be repeated?
What are the risks associated with the test?
The risk of miscarriage due to fetal blood sampling is between 1 and 2%.