Preimplantation Genetic Diagnosis (PGD) or Preimplantation genetic screening(PGS)
Preimplantation Genetic Diagnosis (PGD) is an advanced technique used in
IVF treatment. In this process embryos are analysed for any genetic
abnormalities prior to embryo transfer and before they are implanted in the
uterus. This procedure helps to eliminate embryos with chromosomal
abnormalities or known genetic disorders and thus it increases the chances
of conception after IVF treatment and the chances of having a healthy
child. The method was initially developed as an alternative to prenatal
diagnosis for couples who are at risk of passing on serious genetic diseases
to their children. It thus avoids the need for the termination of
pregnancy.
An increasing number of genetic disorders and chromosomal abnormalities can
now be diagnosed by this technique.
The procedure involves doing an embryo biopsy on day 5 (at the blastocyst
stage of the embryo). Usually 6-10 cells are removed from the outer layer of
cells. The procedure needs high expertise and is carried out by trained
embryologists. The biopsied cells are then analysed for any genetic
abnormalities. Only the embryos found to be normal are used for embryo
transfer later. The abnormal embryos are discarded.
PGD/ PGS is recommended for-
- Couples who have a genetic disorder or are known carriers of genetic disease which can be transmitted to the child.
- Couple who have a child with genetic disorder
- Couples who wish to identify a tissue match for a sick sibling.
- Advanced age of the female partner.
- Recurrent implantation failures after IVF Treatment
- Recurrent abortions
Adequate counselling is needed before PGD/PGS. There is possibility that none of the embryos may be detected as normal and so none will be available for transfer. Also, transferring a normal embryo doesn’t guarantee a successful IVF treatment as there are many other factors which can affect the IVF treatment outcome.