Preimplantation Genetic Diagnosis (PGD) in Delhi, India

According to the National Institute of Health, Preimplantation Genetic Diagnosis (PGD) in Delhi, India is defined as the “ testing of the preimplantation stage embryos or oocytes for genetic defects”. Couples having a high risk of passing on structural chromosomal abnormalities, genetic disorders to their offspring can choose PGD.

Indications of PGD

PGD in India is considered when one or both the parents have any genetic abnormality and want to determine if the embryo also carries it. Some of the indications of PGD are:

• Parents having single-gene conditions such as cystic fibrosis, sickle cell anemia, or BRCA mutations.
• Couples having chromosomal aberrations including translocations, deletions, inversions, changes in chromosome numbers, etc that can cause implantation failure, recurrent pregnancy loss, or physical/mental defects in the offspring.
• Couples with autosomal recessive or autosomal dominant conditions have the risk of affecting the embryo to 25% and 50% respectively.
• Couples with X-linked disorders have a 25% risk of affecting the child. Fragile X syndrome is one such disorder.
• PGD is done for almost all inherited conditions where the exact mutation is known.

How is the procedure performed?

PGD in Delhi, India technique is performed in the laboratory along with In vitro fertilization (IVF) or Intracytoplasmic Sperm Injection (ICSI) procedures. The embryos formed during the IVF/ICSI procedures are allowed to develop to a 6-8 celled stage. One or two cells of embryos developed through IVF/ICSI are isolated, biopsied, and tested either through a polymerase chain reaction (PCR) or fluorescent in-situ hybridization (FISH) methods.

Polymerase chain reaction (PCR): PCR is also known as DNA Amplification where the single strand of DNA is multiplied into several billion copies in less time. The enzyme DNA polymerase helps create similar copies of DNA for easy identification of mutations.

Fluorescent in-situ hybridization (FISH): In FISH, small fluorescent-labeled fragments of DNA also known as probes are used to attach with the cell biopsy sample. These probes attach to the specified chromosomes that are viewed under a fluorescent microscope. This allows the geneticist to distinguish between a normal and abnormal chromosome. Chromosomes analyzed through the FISH technique include X, Y, 1,13,161,18, and 21.

The embryos without genetic variations are transferred into the uterus of the woman for further development. PGD allows the selection of embryos without genetic defects. By doing so, the risk of passing on the genetic defect to the child is reduced