Basic outline of genetic testing of the embryo :

1st step –Genetic counselling to determine if the couple needs genetic test of the embryo & which type of test should be done.

2nd step –IVF /ICSI procedure to get embryos.

3rd step –Blastocyst culture to get embryos with best implantation potential.

4th step –Embryo biopsy : Collection of 5-7 cells from blastocyst stage embryo using special microsurgical instruments.

– Implantation & future growth potential of the embryo is not compromised when biopsy is done on blastocyst stage embryos.

5th step – The genetic material , DNA is extracted from these cells & tested for genetic diseases using specially made genetic test probes.

6th step – Transfer of normal embryo in womb

-In most cases cryopreservation of embryo is required till the final result of genetic test is available

There are 3 type of embryo genetic testing :

(1) Preimplantation Genetic Testing for Aneuploidies ( PGT-A):

• Earlier it was called Preimplantation Genetic Screening ( PGS ).

• The aim is to look for presence of any aneuploidies ( extra or missing chromosome ) of the embryo.

• It can help to select the embryos with normal chromosomal pattern which will have highest chance of becoming healthy babies.

• It is done when there is no known evidence of a genetic abnormality in either parent.

Who can benefit from PGT-A ?

• Female partner age 38 or older.

• Couples interested in single embryo transfer.

• History of repeated pregnancy loss.

• History of repeated failed IVF.

• Couple with more number of embryos can choose to select the normal embryo to decrease ‘ time to pregnancy ‘.

(2) Pre Implantation Genetic Testing for Monogenic Diseases (PGT-M):

• It was earlier called Preimplantation Genetic Diagnosis( PGD ).

• It is recommended when there is known risk of passing down a genetic abnormality to future offspring.

• Genetic test report of affected family member is analysed in details to plan treatment for the couple.

Who can benefit from PGT-M ?

• Personal or family history of single-gene defects—such as cystic fibrosis, haemophilia, sickle cell anaemia, muscular dystrophy, citrullinemia , multiple exostosis etc.

(3) Pre Implantation Genetic tests for Structural Rearrangement ( PGT- SR )

• Chromosomal structural rearrangements are translocations , inversions ,duplications or deletions of part of chromosome.

• Many time carriers of structural rearrangement are apparently healthy individuals.

• Most of the times structural rearrangements are suspected & detected only when such individual suffer from repeated IVF failure, repeated miscarriage or birth defects in their babies.

Who can benefit from PGT-SR ?

• In known carriers of chromosomal structural rearrangement normal embryos can be selected by PGT SR.