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Fetal Blood Sampling

What is fetal blood sampling?

Fetal blood sampling is a procedure to take a small amount of blood from an unborn baby (fetus) during pregnancy. Fetal blood sampling is usually done by a perinatologist with special training. This is a doctor who specializes in the care of babies in high-risk pregnancies.

Why might I need fetal blood sampling?

Fetal blood sampling is a very complex procedure. It must be done by a doctor with special training. It’s done when other tests or procedures are not possible or do not work. It can be done for pregnancies that are 18 weeks or later.

Fetal blood sampling is done as part of diagnosing, treating, and checking problems in the baby at certain times during pregnancy. A fetal blood sample may be taken to:

  • Diagnose genetic or chromosome abnormalities

  • Check for and treat severe anemia in the baby

  • Check for and treat other blood problems such as Rh disease

  • Check oxygen levels in the baby

  • Check for infection in the baby

  • Give certain medicines to the baby

The benefits of fetal blood sampling include:

  • It gives specific information about the baby's health.

  • A baby with severe blood diseases can be treated before birth.

What are the risks of fetal blood sampling?

The risks of fetal blood sampling include:

  • Bleeding from the fetal blood sampling site

  • Changes in the baby’s heart rate

  • Infection

  • Leaking of amniotic fluid

  • Death of the baby

How do I get ready for fetal blood sampling?

You don’t need to do any special preparation before the procedure. Your healthcare provider will tell you if you need to have a full bladder for the test.

What happens during fetal blood sampling?

You will lie in a comfortable position on an exam table. The healthcare provider will clean your belly with antiseptic. He or she will insert a long, thin needle through the belly and into the uterus. This is guided by ultrasound. Blood may be taken from several sites, such as:

  • Blood vessels in the umbilical cord. This is also called cordocentesis. It’s also known as percutaneous umbilical blood sampling (PUBS).

  • A blood vessel in the baby. This is usually in the liver or heart.

Fetal blood transfusions are done using a similar method. The baby either gets blood or has unhealthy blood exchanged for healthy blood. This can treat certain problems. In this case, it may be needed to give a sedative medicine to keep the baby from moving.

What happens after fetal blood sampling?

After the procedure, you’ll need to rest in the hospital. Your baby’s heart rate will be watched for a few hours. You’ll need to have someone drive you home afterward. The results will take several days. You’ll have a follow-up appointment with the perinatologist to discuss the results.

Next steps

Before you agree to the test or the procedure make sure you know:

  • The name of the test or procedure

  • The reason you are having the test or procedure

  • What results to expect and what they mean

  • The risks and benefits of the test or procedure

  • What the possible side effects or complications are

  • When and where you are to have the test or procedure

  • Who will do the test or procedure and what that person’s qualifications are

  • What would happen if you did not have the test or procedure

  • Any alternative tests or procedures to think about

  • When and how you will get the results

  • Who to call after the test or procedure if you have questions or problems

  • How much you will have to pay for the test or procedure

Online Medical Reviewer: Donna Freeborn PhD CNM FNP
Online Medical Reviewer: Heather Trevino
Online Medical Reviewer: Irina Burd MD PhD
Date Last Reviewed: 3/1/2019
© 2000-2020 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.