Fetal Blood Sampling | Percutaneous… | Riley Children's Health

Fetal blood sampling, also known as percutaneous umbilical blood sampling (PUBS) or cordocentesis, is a procedure that involves taking blood directly from the umbilical cord during pregnancy.

Why is fetal blood sampling done?

Fetal blood sampling, or PUBS, is done at any time after 18 weeks of pregnancy to evaluate for several different fetal conditions.

PUBS is often used to diagnose blood disorders, like fetal anemia, but it can also diagnose fetal infections, such as toxoplasmosis and certain genetic conditions.

Your doctor can perform a blood transfusion or deliver medications to your baby during the procedure. This is called intrauterine transfusion (IUT) because it is a blood transfusion given to your baby while still in the womb.

Percutaneous umbilical blood sampling (PUBS) procedure for obtaining a fetal blood sample

Why is intrauterine transfusion (IUT) done?

IUT may be recommended when a fetus has anemia (low red blood cell count, low platelets count). Fetal anemia, if untreated, may result in fetal heart failure (hydrops) and may be caused by:

Maternal alloimmunization: when the mother has antibodies that can transport to the fetus through the placenta and may result in fetal red blood cell destruction resulting in fetal anemia
Some viral infections e.g. Parvovirus B19 viral infection in the mother

What are the risks?

Since this is an invasive procedure, it does come with some risks. These risks include:

Bleeding
Infection to the mother, baby, or both
Preterm labor
Preterm birth
Premature rupture of membranes (PROM)
Fetal distress
Need for emergency cesarean section

Within the Fetal Center at Riley Children’s Health, the highly skilled maternal-fetal medicine physicians specializing in fetal intervention perform this delicate procedure. Our specialists have extensive training and experience and partner with a multidisciplinary team to offer compassionate and expert care. Riley Children’s has performed PUBS for over a decade.

What to Expect

Preparing for your procedure

Before your scheduled procedure, you will be instructed when not to eat or drink. Depending on gestational age at the time of the procedure, some pregnancies might receive steroids prior to the procedure day to fasten fetal lung maturity in case emergency preterm delivery was to occur.

When you arrive at the Riley Maternity Tower, your healthcare team will get you checked in.

About the procedure

There are two methods to perform fetal blood transfusions. In both, a needle is inserted into the mother’s abdomen.

Intravascular transfusion (IVT): blood is transfused into the umbilical cord
Intraperitoneal transfusion (IPT): blood is transfused into the fetus’ abdomen (less common)

In the operating room, the mother is given some form of anesthesia. fetus may be given additional medication to stop movement. Using ultrasound to determine the position of the fetus and placenta, the surgeon inserts a needle into the mother’s abdomen and then into the umbilical cord vein or the fetus’ abdomen. A blood sample is obtained and sent to the lab to determine fetal blood counts following which the calculated needed volume of blood products that are compatible with the fetus’ blood type are passed through the needle into the fetus.

What happens after the procedure?

After your procedure, you’ll need to rest in the hospital while your baby’s heart rate and other vitals are monitored over a couple of hours. Typically, you can leave later in the day after the procedure is performed, but you will need to have someone drive you home.

Fetal transfusions may need to be repeated every few weeks until the fetus is ready to be born.

You will have a follow-up appointment with Riley Maternal-Fetal Medicine or the Fetal Center within a week of the procedure.