There are a host of novel technologies available in the fertility space. Each of these plays a unique role in augmenting the chances of pregnancy for couples unable to conceive. Today, I will spotlight two of the most popular technologies that have taken centrestage in recent years: preimplantation genetic screening (PGS) and preimplantation genetic diagnosis (PGD).
PGS is a test that examines the chromosomal construct of an embryo. It allows embryologists to determine whether the number of chromosomes present in an embryo are adequate. PGS does not necessarily trace for specific diseases; it only aims at gauging the number of chromosomes housed in an embryo. As a result, it increases the chance of a healthy pregnancy for couples across age groups.
PGD involves the examination of an embryonic cell produced during an in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) procedure. It is tailored to test for specific genetic conditions (cystic fibrosis, for example) before transferring the embryo to the uterus.
All pregnancies run the risk of a chromosomal abnormality. In fact, it is estimated that half of human fertilisations carry the wrong number of chromosomes, which is a leading cause of miscarriage. The risk of having a pregnancy with a chromosomal abnormality increases as females age. Unlike men, who produce millions of sperm daily, a woman is born with all her eggs already created. The ability of her eggs to produce a healthy child decreases as she gets older. That is why a woman’s age is critical when considering the probability of getting pregnant.
Any couple undergoing IVF/ICSI can opt for PGS/PGD in order to select a chromosomally normal embryo. If a carefully studied embryo is transferred, the chances of conception increase. Also, the odds of miscarriage and of bearing a child with abnormalities automatically reduce. By and large, PGS/PGD are recommended in the following cases:
A biopsy is usually done at the expanded blastocyst stage after the embryo has split into an inner cell mass, a trophectoderm component and a fluid-filled cavity. For this, a small hole is made in the shell of the embryo and several cells that are precursors to the placenta (trophectoderm) are removed for testing.
A genetic evaluation is performed using PCR, FISH or a comparative genomic hybridisation (CGH) technique. Nonaffected or normal embryos are then transferred into the uterus for implantation, potentially resulting in pregnancy.
Dr. Uma Maheswari
M.B.B.S., D.G.O., Fellowship in Reproductive Medicine
Cloudnine Fertility, JP Nagar, Jayanagar, Bellandur.
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