Prenatal testing can be a scary time for parents. While discovering any birth defects as early as possible allows the best chance for treating them, the prospect of discovering that your developing fetus may have serious health problems is nerve wracking.

Cordocentesis, also known as fetal blood sampling and Percutaneous blood sampling (PUBS), is a method of prenatal testing that’s being used to diagnosis in utero complications, including Down syndrome and heart defects. It’s also becoming a commonly used method of treating defects while the baby is still in utero.

What is Cordocentesis?

Cordocentesis, (not to be confused with amniocentesis, in which amniotic fluid is removed from the area surrounding the developing fetus), is a process in which an advanced ultrasound is used to guide a thin needle directly into the umbilical cord.

Once the needle is inserted, a small sample of fetal blood is retrieved and sent to the lab, where it is checked for red blood cell count, fetal infections, fetal oxygen levels and other markers that indicate the health of the fetus. Results usually become available within 72 hours.

When and Why is Cordocentesis Performed?

Cordocentesis is performed when amniocentesis, or a CVS, is unsuccessful or inconclusive in tracking fetal abnormalities. It is usually performed later in pregnancy, between 18 and 24 weeks, when the umbilical cord is sufficiently developed.

If it is performed after 26 weeks and the baby is in distress, an emergency C-section will be performed, although this is very rare.

Cordocentesis looks for fetal malformations; chromosomal irregularities, such as: Down's Syndrome; blood disorders; fetal anemia, isoimmunization; and infections, such as toxoplasmosis.

Benefits of Cordocentesis

Cordocentesis testing can help parents in many ways. For example, it can be used in the diagnosis of heart defects in utero. It can help expectant mothers prepare for a special needs child, explore medical interventions that might be needed, and in some cases help parents decide whether to carry the child to term.

Risks of Cordocentesis

Cordocentesis does not have a consistent success rate. False positives are a possibility.
While it’s generally considered a safe procedure, it is invasive, and is generally reserved for life and death scenarios.
There is a 1 to 2% risk of miscarriage, with a small risk of infection.
Side effects for the fetus can include: decreased heart rate, infection and blood loss.
Side effects for mom include fever, chills, and leaking of amniotic fluid.
While an anesthetic isn’t required for this process, it can lead to slight discomfort, including cramps and contractions both during the procedure or for a couple of days after.

Cordocentesis: In Utero Treatment

In one instance, a fetus in utero with an irregular heartbeat (called a heart arrhythmia) was administered anti-arrhythmic medication through an injection directly in the his blood stream. This was done after oral medication prescribed to the baby’s mother failed to regulate the his heart rate, which should be an average of 110 to 160 beats a minute.

Cordocentesis has also been used successfully to treat parvovirus in a twin pregnancy.

In utero treatment has been used to repair a congenital heart valve disorder at twenty weeks. In this case, the defect led to a severe narrowing of the aortic valve (a condition which accounts for 8 to 11% of all congenital defects) and left ventricle. The baby wouldn’t have survived had doctors not performed the cordocentesis.

Cordocentesis provides hope that congenital heart defects can be treated before birth, thereby reducing the need for heart surgery during the first years of an infant’s life. It may also be used to treat respiratory problems.

Costs of Cordocentesis

Prenatal tests can be very expensive, the average cost being $255, not including physician’s fees for sample collection or shipping.