Preimplantation Genetic Diagnosis & Screening
Used to identify potential chromosomal disorders
Preimplantation Genetic Diagnosis & Screening
Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS) are advanced techniques used in conjunction with in vitro fertilization (IVF) to assess genetic information of embryos before they are transferred into the uterus. These techniques help identify embryos that are free of certain genetic disorders or chromosomal abnormalities, thereby increasing the chances of a successful pregnancy and reducing the risk of passing on genetic conditions to offspring.
Preimplantation Genetic Diagnosis (PGD) :
PGS is a broader screening technique used to assess the chromosomal health of embryos, particularly looking for numerical abnormalities (aneuploidy) that can lead to implantation failure, miscarriage, or genetic disorders. Here’s how PGS works:
- During IVF, embryos are cultured in the laboratory until they reach the blastocyst stage (typically around day 5 or 6 after fertilization). A few cells are then biopsied from each embryo, and these cells are tested for genetic abnormalities.
- PGD is used when one or both parents carry a known genetic disorder, such as cystic fibrosis, sickle cell disease, or Huntington's disease. It can also be used to screen for chromosomal abnormalities like Down syndrome (trisomy 21), Turner syndrome, or structural chromosomal rearrangements.
- PGD allows for the selection and transfer of embryos that are free from the specific genetic condition or chromosomal abnormality being tested for, potentially reducing the risk of passing on genetic disorders to offspring.
- PGD does not guarantee a healthy pregnancy or eliminate all genetic risks, as it only tests for specific conditions that are targeted in the genetic analysis. It also involves embryo biopsy, which carries a small risk of harm to the embryo.
Preimplantation Genetic Screening (PGS) :
PGD is a procedure used to test embryos for specific genetic conditions known to be present in the parents or to screen for chromosomal abnormalities. Here’s how PGD works:
- Similar to PGD, embryos are biopsied at the blastocyst stage, and the cells are tested to determine if they have the correct number of chromosomes (euploid) or if there are abnormalities (aneuploid).
- PGS is primarily used in cases of advanced maternal age (over 35 years), recurrent miscarriages, previous unsuccessful IVF cycles, or when there is a concern for chromosomal abnormalities.
- PGD allows for the selection and transfer of embryos that are free from the specific genetic condition or chromosomal abnormality being tested for, potentially reducing the risk of passing on genetic disorders to offspring.
- PGS does not detect all genetic disorders or guarantee a successful pregnancy. It also involves embryo biopsy, which carries a small risk to the embryo, and false positive or false negative results can occur.
