PGD – Pre-implantation Genetic Diagnosis

Pre-implantation Genetic Diagnosis or PGD is the process of testing the embryos, created through IVF treatment for patients at risk of having a baby with an inherited illness or condition.

For Whom is PGD Testing Performed

If a patient has a family history of a serious genetic condition, a history of terminations due to discovering their baby has an inherited condition, or perhaps already has a child with the inherited condition, then pre-implantation genetic diagnosis is a technique which is seriously considered. This avoids the probability of passing an inherited condition onto their baby.

PGD clinics are only able to test for conditions that are deemed “sufficiently serious.” There are over one hundred registered conditions, these include but not exclusively;

1. Alpers Syndrome
2. Early onset of Alzheimers Disease
3. Battens Disease
4. Carney Complex
5. Coffin-Lowry Syndrome
6. Cystic Fibrosis
7. Downs Syndrome
8. Hunters Syndrome
9. Muscular Dystrophy
10. Niemann Pick Disease
11. Retinoblastoma
12. Sickle Cell Anaemia
13. Turners Syndrome

There are also conditions which are being considered for PGD testing, which include;

1. Calpainopathy
2. Dravet Syndrome
3. Noonan Syndrome

This kind of testing can be incredible controversial, as the results may often determine whether or not an embryo is allowed to develop. However the long term effects of a child born with an inherited condition can be devastating, for the child and also the parent. For this reason, conditions need to be carefully considered by officials within the government in order to determine the morality of such decisions.

Most approved conditions can be tested by request of the patient, however occasionally the HFEA (The UK’s Human Fertilisation and Embryology Authority) will consider the individual case, prior to making a decision.

What Are the Risks For the Mother and the Fetus?

There are risks associated with PGD treatment, which are similar to those of traditional IVF treatment. These include;

1. Irritability or headaches as a result of the fertility drugs
2. Ovarian hyper-stimulation syndrome or OHSS
3. Miscarriage
4. Multiple Births
5. Embryos may be damaged during cell removal
6. The results cannot be guaranteed to be 100% reliable

Pre-implantation genetic diagnosis can be a lengthy and complicated process, particularly frustrating for a patient waiting for the results of the tested embryo.

Prior to the collection of eggs, medication may be given to prevent the premature release of the eggs, before collection. IVF would then be carried out on the patient in order to collect the eggs and to fertilize them. The patient would be heavily sedated, and the procedure usually takes around 20 minutes. The patient would then be taken to a recovery area, whilst the eggs are transferred to a special incubator ready for testing.

The next stage takes approximately three days as the embryo is grown in specific conditions. However, if the embryo is left to develop for a slightly longer period, this can ensure more accurate results of the testing. An embryologist then carefully removes cells from the embryo for testing. This is a highly specialised process, often using a weak acid to dissolve the outer shell of the embryo in order to collect the cells. The cells are then tested for any abnormalities.

There is a certain risk of damaging the embryos during the testing, as above. This author does not know clearly what are the percentage rates for damage. I saw one site that claimed that the chance for damage was less than 1%, and another site expressed itself that the risk is minimal, but present. I recommend that you discuss this point with your medical professional.

During this time, uterus in preparation for the embryos. The test results then determine whether or not the embryo is then transferred to the womb.

Certain conditions are sex linked disorders, such as Duchenne muscular dystrophy. This means that the embryo’s sex is determined at the testing stage to ensure that only the unaffected sex embryos are transferred to the womb.

When it is time for the transfer of unaffected embryos, an instrument is used similar to that in a smear test, in order to clearly see the cervix. The embryos are then injected into the best possible area of the uterus. This process is much simpler than the extraction of eggs and usually takes no longer than around 15 minutes to complete. Usually no more than 2 embryos are transferred.

It is difficult to determine the success rate of having a child through PGD, as individual circumstances vary enormously. It may be that no embryos are clear of the genetic condition, or the removal of cells has damaged the embryos. And of course, if successful the patient still carries the same risk with pregnancy as anybody else.

The entire process can be rather difficult and frustrating, but the results can be the best possible outcome. Also if there are any remaining unaffected embryos, they may be frozen and stored for future use. This prevents the necessity for further genetic testing or hormone injections for ovary stimulation.

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