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.

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 aren't possible or don't work. It can be done at week 18 of pregnancy 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 a severely low amount of red blood cells (anemia) in the baby
• Check for and treat other blood problems, such as Rh disease
• 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.

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

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

You'll lie in a comfortable position on an exam table. The doctor will clean your belly (abdomen) with antiseptic. They'll insert a long, thin needle through the belly and into the womb (uterus). This is guided by ultrasound. Local anesthesia (medicine injected into your abdomen to numb the skin) or spinal/epidural anesthesia may be used. 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.
• 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 necessary to give a sedative medicine to keep the baby from moving.

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.

Before you agree to the test or 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