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Prenatal and preimplantation diagnosis

Raymond Lepage, PhD
Raymond Lepage, PhD
Senior Scientific Advisor

A prenatal diagnosis (PND) identifies fetal abnormalities or genetic diseases during pregnancy. In the context of a disease already identified in your family, before doing this test, we need to identify whether you have the mutation or, in the case of a recessive transmission disease, whether this mutation is present in both parents. Depending on the disease, even if the mutation is known, the PND can determine whether or not the fetus is affected, but it is not possible to predict the severity of the symptoms.

You can choose one of two procedures for a prenatal diagnosis:

Chorionic villus sampling (placenta biopsy)

  • Done using the DNA extracted from this sample.
  • Undertaken between the 10th and 12th week of pregnancy.
  • An associated risk of fetal loss (miscarriage) of about 1% (1 in 100).
  • An approximately 2% risk of the sample being contaminated with cells of maternal origin. In such cases, the test would not be reliable and an amniocentesis would be required to establish a diagnosis.
  • The accuracy of this prenatal test is assessed at 98%.
  • Results are available 2-3 weeks after the procedure.

Amniocentesis

  • Consists of an amniotic fluid sample.
  • Done using the DNA extracted from this sample.
  • Usually undertaken after the 15th week of pregnancy.
  • An associated risk of fetal loss (miscarriage) between 0.25% (1 in 400) and 0.5% (1 in 200).
  • The accuracy of the test is 99.8%.
  • Results are available 2-3 weeks after the procedure.

As for the Preimplantation Diagnosis (PID), it can detect the presence of potential genetic or chromosomal abnormalities in embryos conceived after in vitro fertilization. In this case, a genetic test is done on a few cells taken from each embryo. Embryos carrying the mutation can therefore be excluded and only unaffected embryos are implanted in the uterus.

The disadvantages of the PID include the associated costs, the ovarian stimulation process, in vitro fertilization, the possibility that few (or no) embryos will be available for transfer and the implantation rate of approximately 30-35%.

If you have any questions or need more information, please don’t hesitate to call our customer service number at 1 833 590-2715.