Cordocentesis Test for Diagnosing Fetal Abnormalities


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Cordocentesis, also referred to as Percutaneous Umbilical Cord Blood Sampling (PUBS) test, is a prenatal diagnostic test that can be used to determine whether there are any abnormalities present in a fetus. It consists of taking a sample of the fetus’s blood from the umbilical cord for further testing.

The test is typically performed after the 18th week of pregnancy and can test for certain genetic conditions, blood disorders, and various infections. If need be, the procedure can also be used to give medication to the fetus through the umbilical cord, as well as blood transfusions.

Cordocentesis isn’t being used as much as it has in the past because there are other prenatal diagnostic tests that can be used instead that are less risky to the fetus, like amniocentesis or chorionic villus sampling (CVS). If other tests aren’t yielding enough information, though, cordocentesis is still performed.


Between weeks 18–23, cordocentesis is usually done right in your provider’s office. After 24 weeks, it’s done in a hospital in case there are any complications that might require an emergency C-section. When it’s done in the hospital, you’re usually asked to fast after midnight in case surgery is necessary.

First, an ultrasound is done to locate where the umbilical cord inserts into the placenta. Using ultrasound guidance, a very thin needle is inserted through the abdomen and uterine wall into the umbilical cord to get the sample of blood. It is then sent to the lab and results typically take around 72 hours.

After the procedure, you and the fetus might be monitored for a bit and you might feel some light cramping. Your obstetrician or midwife may suggest bed rest for the rest of the day, but you will usually be able to resume your typical routine the next day.

If you notice anything out of the ordinary like vaginal bleeding or leaking fluid, or develop symptoms like a fever or chills, it’s important that you call your maternity care provider.


As with any procedure, cordocentesis does carry risks to both the mom and the fetus. While safe, it is considered an invasive procedure. According to the American Pregnancy Association, miscarriage is the main risk of cordocentesis, with one to two miscarriages for every 100 procedures. The procedure does have a higher risk of miscarriage than other prenatal diagnostic tests, which is why its popularity is declining.

Other possible risks of cordocentesis can include:

Before deciding to go through with the procedure, talk with your doctor about all of the possible risks and what this might mean for you. Depending on your medical situation, location of the placenta, the health of the fetus, and your medical history, your doctor will be able to discuss whether this is an appropriate procedure to undergo and what risks are most pertinent to you.


People decide to have cordocentesis performed for a variety of reasons, especially if the other prenatal diagnostic tests are unable to be done for any reason. Although the procedure cannot test for neural tube defects, it can detect chromosomal abnormalities, blood disorders, fetal malformations, fetal infection, and fetal anemia.

An important thing to remember is that though the test is able to detect any abnormalities or issues with a high degree of accuracy, the test does not measure the severity of these issues. Your maternity care provider, along with a genetics professional, can help you navigate any results you get, answer questions you might have, and provide you with all of the information and options available to you.

If you decide to have the procedure done, the results can help you start planning for a child with different needs, find support groups and resources, or start exploring medical treatments for your child. You might also choose not to have the procedure done, which is also a valid decision.

Cordocentesis can be a valuable prenatal diagnostic test when other tests are not able to be performed. As with any medical procedure, it does have its risks. If your provider mentions cordocentesis, talk with her about why the test is being recommended, the particular risks and benefits to you and your situation, and what other options are available to you.

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By Jaime R. Herndon, MS, MPH
Jaime Rochelle Herndon, MS, MPH, MFA, is a former writer for Verywell Family covering fertility, pregnancy, birth, and parenting.