Chorionic Villus Sampling During Pregnancy


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Modern technology allows parents to be an opportunity to look into the health of an unborn child well in advance of birth. While this raises some ethical develop in medical circles, these tests are broadly being used at present to monitor the health of embryos and foetuses during the early stages of both pregnancy and artificial reproductive techniques like IVF (in vitro fertilisation). Chorionic Villus Sampling is one example of such techniques, and this article should provide you with more information about how to proceed with the test if you wish to do so.

What is Chorionic Villus Sampling?

Chorionic Villus Sampling, also known as CVS, is a method of testing a foetus for genetic illnesses at very early stages of development. CVS can’t detect every possible developmental issue, but can provide an insight into whether the faulty genes causing conditions like Down’s Syndrome are present in a developing foetus.

What conditions can Chorionic Villus Sampling detect?

CVS can detect a range of different disorders with a genetic basis like:

  • Cystic fibrosis – a genetic illness in which cells lining the airways produce copious amounts of a thick, viscous secretion.
  • Down’s syndrome – where a foetus has an extra chromosome which causes impairments in mental and physical development.
  • Muscular dystrophy – a genetic illness which is characterised by a steadily worsening muscular weakness which ultimately results in disability.
  • Phenylketonuria – a metabolic illness caused by a genetic defect which means your body can’t produce important enzymes (important biological molecules with many important roles).
  • Thalassemia and Sickle Cell Anaemia – common blood conditions which can limit the ability of your red blood cells to effectively transport oxygen around the body. How does Chorionic Villus Sampling work?

A CVS test basically involves an experienced medical professional extracting a small sample of cells from a part of the placenta. These cells are where the test derives its name from as they are called the chorionic villi, and upon a study of the genes in these cells, the genetic health of a developing embryo can be determined.

How is Chorionic Villus Sampling performed?

There are two different methods of extracting chorionic villi safely for study, these are the transabdominal and transcervical methods. In both cases, an ultrasound machine is used to guide the procedure, allowing the medical practitioner performing the study a means by which to see what exactly is going on and keep the procedure safe.

The transabdominal method of CVS involves going through the stomach, while the transcervical method involves a different route through part of the female reproductive tract called the cervix. This is essentially the base of the womb/uterus.

If the transabdominal method is used then you can expect your stomach to be cleaned with antiseptic before a needle is passed through the wall of your abdomen (guided by an ultrasound scan). The needle is extremely fine and is used to extract cells via an attached syringe.

The transcervical approach is very similar, but takes a slightly different route as mentioned previously. This time the antiseptic treatment will be applied to the cervix and vagina, and a specially designed tube will be passed through the vagina under guidance from an ultrasound scan and used to extract chorionic villus cells.

Once cells have been extracted safely, they are screened for genetic anomalies for illnesses like cystic fibrosis, Down’s syndrome, and many other debilitating and lifelong conditions that can have a huge impact on both the future child and family.

The route or method of CVS chosen depends on the position of your placenta, but generally speaking transabdominal CVS is used more often because it is known to be more safer.

What are the risks involved in Chorionic Villus Sampling?

Because CVS involves getting a sample from the cells of a vulnerable, developing embryo, there is an element of risk involved. Between 1% and 0.5% of CVS tests can result in a miscarriage, and on top of that there are other risks like the chances of an infection or amniotic fluid leakage. Amniotic fluid is found within the womb and is an important protective substance which, when leaked, can be detrimental the health of both mother to be and foetus.

Should I have Chorionic Villus Sampling?

You will only be offered a CVS test if there is a strong incidence of life changing genetic illnesses like Down’s Syndrome in your family. Because of the potential for miscarriage and infection, CVS is not a routine test, and you can expect your doctor to go through all the pros and cons in detail prior to any testing.

What should I do if a CVS test comes back positive for a genetic illness?

The choice of what to do after a CVS test has been performed is yours and your partners. Since the test is designed to look for genetic disorders that can severely impinge on a developing embryo’s potential future health, many parents are faced with a major decision about whether to proceed with the pregnancy or not. This is a very personal decision, and one which your doctor and/or midwife won’t be able to help you with beyond providing any support you need.

CVS testing provides parents to be with a chance to ascertain the health of a developing embryo. However the choice of what to do with a positive result can be very difficult, and moreover the potential risks of a miscarriage or infection mean that the decision about whether or not to proceed with the test itself is a major step in itself. Whether you are receiving your care through the NHS or Privately, you should consider whether you want to proceed with Chorionic Villus Sampling carefully.


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