Children's Health and Wellness

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. Fetal blood sampling is usually done by a specially trained perinatologist, a doctor who specializes in the care of the fetus in high-risk pregnancies. It is done 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 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 done 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 done by a specially trained doctor. It is used when other tests or procedures are not possible or not effective. It can be done for pregnancies that are 18 weeks or later.



  • Bleeding from the fetal blood sampling site

  • Changes in the fetal heart rate

  • Infection

  • Leaking of amniotic fluid

  • Fetal death

  • Specialized information about the health of the fetus can often be obtained

  • Fetuses with severe blood damaging diseases can be treated before birth

Print Source: Up To Date. Fetal Blood Sampling
Online Source: The American College of Obstetricians and Gynecologists. Screening for Birth Defects
Online Editor: Metzger, Geri K.
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Online Medical Reviewer: Trevino, Healther, M., BSN, RNC
Date Last Reviewed: 9/28/2014
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