Fetal Blood Sampling (PUBS)

During pregnancy, mothers are constantly poked and prodded for different tests to ensure that they and their child are healthy. The majority of the time, any blood tests that are done will involve taking a blood sample from the mother. However, in some instances, a blood sample may be taken from the baby. This is known as fetal blood sampling.

What is Fetal Blood Sampling?
Fetal blood sampling is a diagnostic procedure to test the fetal blood of a pregnant woman during the second trimester, usually by the 17th week of pregnancy. Also known as percutaneous umbilical blood sampling (PUBS), fetal blood sampling is used to check for fetal anemia, genetic or chromosomal abnormalities, check for fetal infection, fetus oxygen levels, red blood count and to give medication to the fetus. The procedure is usually performed on an outpatient basis and can take several hours to complete. A highly trained physician, a maternal-fetal medicine specialist or a perinatologist performs the test.

How is it Performed?
The test may be done in a hospital or doctor’s office. You will be asked to lie down on an examination table. Your abdomen will be cleansed with antiseptic solution. The doctor will use an ultrasound to locate the uterus in the abdomen, and then insert a needle into either a fetal blood vessel or the umbilical cord to withdraw about a teaspoon of blood. The blood sample will be taken to a medical laboratory for analysis.

After the Test
After the procedure, you will be required to rest for about an hour while your baby’s heart rate and your heart rate are monitored. Following the test you should avoid strenuous activity for about 24 hours and contact your doctor if you experience any abdominal cramps, bleeding, leaking of amniotic fluid or anything that feels unusual.

Who Has this Procedure Done?
Fetal blood sampling is done after amniocentesis and ultrasound are performed. It is usually only offered to people if the amniocentesis and ultrasound have revealed that the fetus has moderate to severe anemia or if the other tests have not revealed enough information about the fetus. The results can be ready in a matter of days.

Risks of Fetal Blood Sampling
Although the test can reveal important information about your baby, there are some risks associated with it:


  • 1 in 100 risk of miscarriage
  • Bleeding from needle puncture site
  • Drop in fetal heart rate
  • Infection
  • Leaking of amniotic fluid
  • Premature rupture of amniotic sac


Benefits of Fetal Blood Sampling(PUBS)
Some of the advantageous of having this test done include:


  • Only procedure that can determine fetal anemia
  • Test results ready within days
  • Blood disorders can be identified and treated
  • Check for infectious diseases like toxoplasmosis, rubella or cytomegalovirus
  • Allows parents to make informed decisions about their baby


Be sure to discuss all the pros and cons of this procedure with your partner and your health care provider if you are considering having the test done.

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