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.

Alternatives to Cordocentesis: Non Invasive DNA Testing

Cordocentesis is sometimes used to confirm whether a woman is carrying a Down syndrome child. It is however, carried out very late during pregnancy and has a higher risk of miscarriage than other invasive tests carried out earlier. In most countries, terminating a pregnancy at 26 weeks is illegal and thus, a woman who seeks to know whether or not her unborn baby has Down’s is probably only doing so to prepare for the birth of a Down syndrome child and to start learning about how to care for one of these special need children.

The risk of miscarriage does remain an issue and is of primary concern for the mother or couple. Miscarrying can result in health complications for the mother not to mention, the emotional turmoil it can create, all the more in such an advanced stage of pregnancy when the emotional bond is stronger.

NIPT testing or Non Invasive Prenatal testing is an ideal test to use to help know whether or not the unborn baby suffers from Down syndrome. It is a 0% risk test done with blood samples. The maternal blood supply will, at any stage during pregnancy, carry varying amounts of fetal DNA.

This DNA finds its way in the maternal blood stream through the placenta which brings the blood supply of the mother and of the fetus almost into direct contact with each other. Through the placenta, dead fetal cells find their way into the maternal blood supply and certain laboratories can isolate the fetal DNA in a maternal blood sample using highly advanced methodologies.

NIPT testing means an expectant mother does not need to undergo any invasive prenatal testing methods like percutaneous umbilical cord sampling, amniocentesis and CVS. Although the non invasive DNA is highly sensitive and can effectively detect Down’s in most cases, there is a small chance (around 2%) of having a false positive result.

In this case, the test results will confirm the presence of a Down’s baby when in fact, the baby will not have Downs. Equally, there is also a chance of false negatives.

Paternity Testing and Non Invasive Testing

It is possible to carry out non invasive prenatal paternity DNA testing. The sampling method is exactly like the non invasive prenatal paternity test for Down’s syndrome – a blood sample needs to be withdrawn from the mother. However, being that the aim of a non invasive prenatal paternity test is to determine the paternity of the baby, it is clear that a blood sample will also need to be collected from the father. Non invasive prenatal paternity testing is 99.9% accurate and possible to carry out at just 10 weeks starting from the first day of the last menstrual cycle. A number of laboratories, including Genetic Testing Laboratories provide non invasive DNA testing for paternity whereby clients receive a sample collection kit containing blood collection tubes, set an appointment with a professional to collect the blood samples and send these off to the lab for analysis.

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.
  • Occasionally, vaginal bleeding or leaking of the amniotic fluid will occur. Women are told to allow for a 24-hour period of complete rest after undergoing cordocentesis.

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.

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