Pre genetic diagnosis( PGD ) is an advanced technique in IVF /ICSI treatment. It basically involves taking biopsy from the embryo generated by IVF and testing it for a specific genetic disease. It is done in those couples where the husband or wife is suffering from a genetic disease that can be transmitted to their newborn child.
PGD involves IVF OR ICSI procedure. To prepare the patient for IVF or ICSI injections are given to the mother to produce multiple eggs in the ovary. The eggs are taken out in the OT by a procedure called Ovum Pick up, done under General Anaesthesia and ultrasound guidance. It is a painless, Daycare procedure which involves no cut or stitch.
Each egg is then injected with sperm ( known as ICSI procedure ). The embryos are then made inside the laboratory and biopsy is done on the embryos to obtain a cell which is then sent for genetic analysis. This is known as PGD ( pre genetic diagnosis). Biopsy is usually done at the Blastocyst stage (D5). After the biopsy, blastocysts are frozen as biopsy reports take 2-3 weeks.
Genetic evaluation is performed using PCR, FISH, or comparative genomic hybridization (CGH). Once the report is generated, then the patient is prepared for frozen embryo transfer and normal embryos are then transferred into the uterus for subsequent implantation/pregnancy.
The genetic diseases which can be detected with the help of PGD can be single-gene disorders like thalassemia, sickle cell disease, or sex-linked disorders like hemophilia or chromosomal disorders which involve inversions, translocations, or deletions.
PGD is a diagnostic test that confirms whether a specific genetic abnormality which is present in one or both the parents is transmitted to their embryo. Before doing a PGD IVF cycle, the couple should consult a geneticist to evaluate the risk of transferring their genetic abnormality to their offspring. The geneticist confirms the diagnosis. The risk of transmission is ascertained and also it is ensured whether currently, available technology can identify that genetic change in a polar body, cleavage state, or blastocyst embryo biopsy.
Embryos can be taken up for biopsy to day 3 or day 5. Each stage for biopsy has its own limitations. Although the blastocyst biopsy is more convenient and safe, the risk of contamination, inadequate D.N.A to detect the genetic disease in question, or mosaicism (i.e, the embryos may be composed of more than one population of the cell) are potential limitations.
The patient also has to be mentally prepared that after the biopsy report, they may not have any healthy embryo for transfer. Even with a successful IVF and PGD procedure, pregnancy is not guaranteed after the transfer, and a term or near-term delivery is also not guaranteed.
PGD technique has few technical limitations and is costlier affair.
The alternative treatments such as donor gametes are also an option for the patients who can not afford or don’t want to try for PGD.
Its always better to understand the entire procedure, associated cost, and success rate in detail from your treating doctor before advancing for the procedure.
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