PGD and Gender selection (Pre-implantation diagnosis) in Iran
Pre-implantation diagnosis (PGD) allows the parents to detect the embryos with inherited genetic disorders and to select their baby's gender.
PGD and Gender selection (Pre-implantation diagnosis) in Iran :
- Duration : 3 Days
• To detect genetic disorders before fertilization and transferring the embryo to the mother’s womb
• To detect and select the embryos with the parent's preferred gender before implantation in the mother's womb
PGD AND GENDER SELECTION (PRE-IMPLANTATION DIAGNOSIS) IN IRAN: ALL YOU NEED TO KNOW
PGD or PGT is a technique of prenatal diagnosis to gain information about the genetic structure of blastocysts created in vitro. A blastocyst is an embryo (5th day of formation). In PGD, 3 to 8 cells are removed through biopsy. Then, the gens are tested in the lab. The embryo then will be frozen for future use. PGD is used to detect around 200 inherited single-gene disorders. Accordingly, affected and unaffected embryos are diagnosed with 98% accuracy.
PGD is not a therapeutic procedure so it doesn’t change the DNA or genetic structures. In contrast, it is a diagnostic procedure that can identify whether the embryo has inherited a single-gen disorder or a chromosome abnormality that could cause physical and developmental disability, miscarriage or unsuccessful implantation of the embryo. Besides, this technique can identify the gender of the baby.
Other prenatal diagnosis techniques are performed during an ongoing pregnancy where the parents should decide whether to abort the fetus or keep it. However, in PGD the level of decision-making is that of choosing the most viable embryos to be transferred to the uterus. For many parents that is the only acceptable decision. Since PGD is done on several embryos in IVF, it has a numerical advantage, which leads to a higher chance of identifying embryos with normal genetic structures.
What are the causes to implement PGD?
PGD is commonly used in the following situations:
• The parents are carriers of genetic diseases such as sickle cell anemia and cystic fibrosis accordingly, they don’t want to inherit it to their child.
• There is a family history of sex-linked disease such as Duchenne muscular dystrophy.
• Maternal age is high and egg quality is low.
• Identifying the cause of unexplained infertility and unsuccessful IVF.
• Selecting the sex of the baby to avoid genetic disorders in males or simply according to parent’s preference which is known as “social sexing”.
• Finding the immunological match embryos for the siblings in need of stem cells for bone marrow transplantation (stem cells from the baby’s cord blood). This baby is called “savior baby”.
What are the preparations for PGD?
Some parameters can influence the success rate of PGD and pregnancy:
• Weight of the female partner: overweight women may not respond to ovulation stimulating medication, the scan pictures during egg retrieval aren’t clear in this condition and there is a higher chance for complications during pregnancy including miscarriage. Therefore, losing weight is strongly recommended for obtaining better results.
• Smoking: Smoking reduces the number and quality of sperms and lowers the success rates of IVF.
• Alcohol consumption: consuming alcohol decreases the number of moving sperms in men. There is no evidence of alcohol affecting women's fertility. However, since alcohol consumption is prohibited during pregnancy, the preparation time for PGD can be a good chance to limit your alcohol intake.
What are the possible risks of the PGD?
The possible risks that are specific to PGD may include:
• IVF possible risks accompanied by PGD
• Ovarian hyper stimulation syndrome
• Pelvic infection after egg retrieval
• Multiple pregnancies
• Birth defects that are not associated with genetic tests
• Damaging the embryos during biopsy or freezing process (rarely and not significant compared to not testing the embryos because the odds of having a healthy child increases with transferring of genetically viable embryos)
• False-negative results which lead to discarding healthy embryos and transferring genetically defective embryos
• This is considerable that PGD cannot screen the embryos for every possible genetic disease.
What to expect from a PGD?
All of PGD types require IVF to obtain the embryos, biopsy of embryos for the test and then thawing the selected embryos to be transferred to the uterus. Following ovulatory stimulation and retrieving of eggs and sperms, the eggs are fertilized with the sperms through ICSI procedure. After 5 to 6 days of culture, the fertilized eggs reach the blastocyst stage. In this stage, the embryo is comprised of 100 to 150 cells. The embryologist extracts 2 to 10 cells through biopsy and prepares it for genetic testing.
PGD has been presented in three types:
• Preimplantation genetic testing for single-gene disorders (PGT-M): the aim of this test is providing a pregnancy with unaffected embryos by genetic mutation carried by one or both parents. This test is also used for gender selection and selecting embryos with specific immunological characteristics (HLA testing for finding the match to the sibling's cells). PCR is a common diagnostic method in PGT-M. Couples who are carriers of a specific genetic disease are more likely to pursue this method. The results will be ready after 7 to 10 days.
• Preimplantation genetic testing for structural rearrangements (PGT-SR): this method aims to establish a pregnancy unaffected by a structural chromosomal abnormality in couples with balanced deletion/duplication and translocation. This technology can distinguish normal noncarrier embryos from balanced carriers. NGS is the newest technology to analyze the chromosomal structure of the cells. This method benefits from bioinformatics and data analysis.
• Preimplantation genetic testing for aneuploidy (PGS): In this method the number of chromosomes is determined. A healthy embryo has 23 chromosomes. This method aims to identify embryos affected by de novo aneuploidy (chromosomal defects) comprising sub chromosomal deletions and additions (duplications) in embryos of normal couples. The abnormal number of chromosomes can be originated from congenital conditions or age (for example Dawn syndrome). The results are often ready following 7 to 10 days.
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