PGD is a type of test that is performed on embryos in the laboratory 5 or 6 days after egg retrieval. A small sample from each appropriately-developing embryo is removed for the purposes of testing. PGD gives us information about each embryo tested. The chromosomal information obtained in the PGD results indicates whether the embryo is male or female, or if there are any chromosome abnormalities such as Down syndrome or types of chromosomal abnormalities that can often be the cause of miscarriage. Our test includes information about the 24 different chromosomes with 98% accuracy. PGD can never be 100% accurate at any laboratory due to the limitations of working with embryos.
PGD is a form of early prenatal diagnosis that is used to detect chromosomal abnormalities in the resulting embryo. It identifies embryos at risk and allows for the prevention of transmission of inherited diseases to the next generation and/or a possible miscarriage during the pregnancy. The embryos used in PGD are created through either IVF or ICSI treatment.
Who should be treated with PGD?
PGD should be offered for 3 major groups of disease: (1) sex-linked disorders, (2) single gene defects, and (3) chromosomal disorders.
These include the following:
Genetic causes
Couples with a family history of X-linked disorders (Couples with a family history of X-linked disease have a 25% risk of having an affected embryo [half of male embryos].)
Couples with chromosome translocations, which can cause implantation failure, recurrent pregnancy loss, or mental or physical problems in offspring
Carriers of autosomal recessive diseases (For carriers of autosomal recessive diseases, the risk an embryo may be affected is 25%.)
Carriers of autosomal dominant diseases (For carriers of autosomal dominant disease, the risk an embryo may be affected is 50%.)
Primary candidates for PGS can include the following:
Women of advanced maternal age more than 35
Couples with a history of recurrent pregnancy loss/abortions
Couples with repeated IVF failure
Male partner with severe male factor infertility
For Gender selection (also gender-based hereditary diseases )
These patient populations are at risk of failure with IVF because of a high proportion of aneuploid embryos. PGD is believed to decrease this risk by selecting chromosomally normal embryos that have a higher chance of implantation.
How is the PGD performed?
Pre Implantation genetic diagnosis (PGD) starts with the standard process of egg retrieval following Ovulation Induction and then fertilization of the eggs in a laboratory through IVF or ICSI. The resulting embryos undergo cell division that is monitored. By means of a state-of-the-art laser, a hole is drilled into a 3-day-old embryo and a single cell is harvested for biopsy purposes. Once biopsied and approved, the embryo may be transferred into the woman’s uterus.