Cordocentesis, also sometimes called Percutaneous Umbilical Cord Blood Sampling (PUBS), is a diagnostic test which examines blood from the fetus to detect fetal abnormalities.
How is cordocentesis performed?
An advanced imaging ultrasound determines the location where the umbilical cord inserts into the placenta. The ultrasound guides a thin needle through the abdomen and uterine walls to the umbilical cord. The needle is inserted into the umbilical cord to retrieve a small sample of fetal blood.
The sample is sent to the laboratory for analysis, and results are usually available within 72 hours.
The procedure is similar to amniocentesis, except the objective is to retrieve blood from the fetus versus amniotic fluid.
When is cordocentesis performed?
Cordocentesis is usually done when diagnostic information cannot be obtained through amniocentesis, CVS, or ultrasound, or if the results of these tests were inconclusive. Cordocentesis is performed after 17 weeks into pregnancy.
What does the cordocentesis test look for?
Cordocentesis detects chromosome abnormalities (i.e. Down syndrome) and blood disorders (i.e. fetal hemolytic disease.).
Cordocentesis may be performed to help diagnose any of the following concerns:
- Malformations of the fetus
- Fetal infection (i.e. toxoplasmosis or rubella)
- Fetal platelet count in the mother
- Fetal anemia
This test is different from amniocentesis in that it does not allow testing for neural tube defects.
What do cordocentesis results mean?
Cordocentesis is a diagnostic test that detects chromosome abnormalities and certain blood disorders with high levels of accuracy. Although the probabilities of identification are high, this test does not measure the severity of these disorders. This test also does not help identify neural tube defects.
What are the risks and side effects to the mother or baby?
Although cordocentesis is considered a safe procedure, it is recognized as an invasive diagnostic test that does pose potential risks. Miscarriage is the primary risk related to cordocentesis, occurring -1-2 times out of every 100 procedures.
Other potential side effects include:
- Blood loss from the puncture site
- Drop in fetal heart rate
- Premature rupture of membranes
Contact your healthcare provider if these symptoms remain or get worse.
You should also contact your healthcare provider if you experience:
- Leaking of amniotic fluid
What are the reasons to test or not test?
The reasons to test or not vary from person to person, couple to couple, and physician to physician.
Performing the tests and confirming the diagnosis provides you with certain opportunities:
- Pursue potential medical interventions that may exist
- Begin planning for a child with special needs
- Start addressing anticipated lifestyle changes
- Identify support groups and resources
Some individuals or couples may elect not to pursue testing or additional testing for various reasons:
- They are comfortable with the results no matter what the outcome is
- Because of personal, moral, or religious reasons, making a decision about carrying the child to term is not an option
- Some parents choose not to allow any testing that poses any risk of harming the developing baby
It is important to discuss the risks and benefits of testing thoroughly with your healthcare provider. Your healthcare provider will help you evaluate if the benefits from the results could outweigh any risks from the procedure.
Compiled using information from the following sources:
1. Danforths Obtsetrics and Gynecology Ninth Ed. Scott, James R,et al, Ch.6
2. William’s Obstetrics Twenty-Second Ed. Cunningham, F. Gary, et al, Ch. 13.