What is PGD ?
PGD is a technique used throughout IVF-ET, wherever embryos square measure tested for malady genes and solely healthy embryos square measure transferred into a female internal reproductive organ.
PGD – however may be a diagnosing created ?
Embryos square measure obtained by combining eggs and sperm cell within the laboratory. From every embryo, one or 2 blastomeres are removed and tested. If the embryo is judged to be freed from the disorder, are transferred to the cavum.
What square measure the indications for PGD ?
Indications for PGD square measure –
Advanced maternal age ( > thirty nine years)
Repeated IVF/ICSI –ET failure cycles
Unexplained physiological condition
Known genetic causes.
What does PGD/PGS involve?
All couples requesting PGD must first undergo an IVF cycle to stimulate the ovaries to produce a number of eggs. These eggs are collected and fertilised using the male partner’s sperm. The resulting embryos are cultured in the laboratory. Embryo biopsy can be performed either on Day 3 or Day 5 after egg collection. Embryos that have developed to at least 5-6 cells are suitable for biopsy. A hole is drilled in the outer shell of the embryo using laser and 1 or 2 cells are removed for genetic analysis. This procedure which is done at the 3rd day gives us the chance of having fresh transfer on the 4th or 5th day. The embryos are kept in culture while the testing of the biopsied cells proceeds. Genetic test results are usually obtained within 24 hours of embryo biopsy. Our embryologists will discuss the PGD results with the couple at the completion of testing. When available, one or two unaffected embryos can be transferred on Day 4 or Day 5. When a number of embryos are identified as being genetically suitable for transfer, morphological criteria are used to determine the best embryo/s for transfer. Surplus unaffected embryos will be grown in culture to Day 5 or Day 6. If they reach an appropriate stage of development (ie: form a good quality blastocyst) they will be frozen. These embryos may be used in a subsequent IVF cycle if the couple do not achieve a pregnancy with the fresh embryo/s. Embryos that are affected or have a chromosome abnormality are discarded.
However, For the last two years, we prefer performing PGS (Preimplantation Genetic Screening ) procedures ( not targeting a specific disease ) at the 5th day instead of the 3rd day. We wait until the 5th day after the egg collection to choose the best ones and make the embryo biopsy from the trophectoderm cells instead of the embryo itself. So, the risk of damaging the embryo becomes virtually zero ( which was estimated to be around 5 % with the Day 3 biopsy) and also the number of the embryos to be screened decreases causing a lower cost. We use NG-CGH (Next Generation Comparative Genomic Hybridization ) technology to check all ( 24 pair ) the chromosomes of the embryos for screening purposes such as advanced maternal age or repeated implantation failures.
A debatable disadvantage about this procedure ( Day 5 biopsy ) is that we should freeze the embryos since the results will be available in 24 to 36 hours which can be too late for the fresh transfer. The only problem is that couples come to our centre again in two or three months for only a few days for the transfer of the healthy embryos found. Besides, our statistics shows that the pregnancy rates are exactly the same as the fresh ones. Furthermore, some recent studies reveals that transferring the frozen embryos may give even higher implantation rates since ovarian stimulation with high dosage of hormones may impair the endometrial receptivity. It is very easy to have frozen embryo transfer. Otherwise, transfer is cancelled. But we think that this is much better than realising the baby is not healthy during the pregnancy with a probable miscarriage..