What Is Preimplantation Genetic Diagnosis (PGD)?
PGD is used to diagnose embryos for known genetic disorders in both partners such as:
- Beta Thalessemia Trait
- Sickle Cell
- Cystic Fibrosis
- SMA 1
- Tay Sachs
- Fragile X
- Downs Syndrome
What Is Preimplantation Genetic Screening (PGS)?
Preimplantation genetic screening (PGS) screens embryos to ensure 23 pairs of chromosomes (22 autosomes and the sex chromosomes X & Y) are present and there is no aneuploidy. PGS is done in:
- Women of advanced maternal age
- Couples with history multiple miscarriages
- Couples with previous IVF failure
- Male factor infertility
How is PGS/PGD performed?
- The PGS treatment involves the basic steps of IVF
- Hormonal injections to grow multiple eggs in the ovaries
- Removing the eggs through trans vaginal aspiration
- Fertilization of eggs with sperms in IVF laboratory
- Biopsy of embryos on day 3 or day 5 (preferable)
- In day 3 embryo, blastomere is extracted from the 6-8 cell embryos and sent for the PGS/PGD in the genetic lab. If the results are good, healthy embryos can be transferred in the uterus on day 5.
- In day 5 blastocyst, the biopsy of the trophectoderm is sent for the PGS/PGD. If the results are good, the embryos are frozen for the next cycle.
What are the risks involved with PGS/PGD?
- PGD and PGS requirein vitro fertilization (IVF), which in itself is associated with certain risks such as ovarian hyper stimulation syndrome, multiple pregnancy, and increased risk of birth defects.
- Biopsy or freezing that is done during the process may harm the embryo(s).
- False negative results can occur i.e. genetic abnormalities are there in the embryo but cannot be detected during the testing. This can lead to the transfer of abnormal embryo in the uterus causing miscarriage. Also, healthy embryos are discarded, reducing the chances of a healthy pregnancy.
- There is no guarantee of a healthy baby since this test does not screen for all possible genetic diseases or disorders.
What are the benefits of PGS/PGD?
- PGD and PGS can help detect known genetic diseases or chromosomal abnormalities in the embryo. This can prevent unhealthy embryos from being transferred to uterus.
- Decreases risk to couples or individuals with serious inherited disorders of having children affected with same problem.