High-Risk Pregnancy - Fetal Blood Sampling

What is fetal blood sampling?

Fetal blood sampling is a procedure to remove a small amount of blood from the fetus during pregnancy. In the past, fetal blood sampling was used only during labor through the mother's open cervix to test blood from the fetal scalp for oxygenation. Today, in many perinatal care centers, fetal blood sampling is performed by specially trained perinatologists as part of diagnosing, treating, and monitoring fetal problems at various times during pregnancy. A fetal blood sample may be taken to:

• Diagnose genetic or chromosome abnormalities
• Check for and treat severe fetal anemia or other blood problems such as Rh disease
• Check for fetal oxygen levels
• Check for fetal infection
• Give certain medications to the fetus

How is fetal blood sampling performed?

There are several ways blood can be obtained from the fetus. After cleansing the mother's abdomen with antiseptic, a long, thin needle is inserted into the mother's uterus guided by ultrasound. Blood may be taken from the following sources:

• Blood vessels of the umbilical cord (also called cordocentesis, or percutaneous umbilical blood sampling, or PUBS)
• A fetal blood vessel, usually in the liver or heart

Fetal blood transfusions are performed using a similar technique. The fetus either receives blood or has unhealthy blood exchanged for healthy blood to treat some problems. In this case, it may be necessary to give a sedative medication to keep the baby from moving.

After a fetal blood sampling procedure, mothers will need to rest in the hospital and have the fetal heart rate monitored for a few hours.

What are the risks and benefits of fetal blood sampling?

Fetal blood sampling is a very complex procedure that must be performed by a specially trained physician. It is used when other tests or procedures are not possible or not effective. It can be performed for pregnancies that are 18 weeks or later.

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