Chromosomal Abnormalities in Embryos | Dr Kaushiki Dwivedee

Chromosomal Abnormalities in Embryos: 

Chromosomal Abnormalities in Embryos stimulated during IVF is encounters more common

The possible reason for the stimulation of eggs which were abnormal and meant to have atresia and not grow further. We tend to stimulate them with a high level of FSH than normal and thus a lot of embryos which grow in culture are chromosomally abnormal. That’s the reason the IVF success rate is 35 % and not 100%.

Also chromosomal abnormalities like Down’s syndrome increase with increasing maternal age. With the passage of time, the egg quality isn’t as good.

Most of the women undergoing IVF in the higher age group and thus increased chance of aneuploidy.

There are ways to detect chromosomally abnormal cells Preconception by PGT-A as well post conception by getting tested for it by NIPT which tests placental DNA

A chromosomal abnormality occurs when an embryo has the wrong number of chromosomes, the wrong amount of DNA within chromosomes, or structurally flawed chromosomes. These abnormalities can translate into the development of congenital abnormalities, disorders such as Down syndrome, or possibly miscarriage.

Understanding Genes And Chromosomes

Your body is made up of cells. In the middle of each cell is a nucleus, and inside the nucleus are chromosomes. Chromosomes are essential because they contain genes that determine your physical characteristics, your blood type, and even how susceptible you will be to certain diseases. Each cell in the body typically includes 23 pairs of chromosomes—46 chromosomes in total—each containing approximately 20,000 to 25,000 genes.

Half of a person’s chromosomes come from the egg of one biological parent and the other half from the sperm of the other biological parent.

What are Chromosomal Abnormalities?

Chromosomal abnormalities are differences in chromosomes that can occur during development. They can be “de novo” (unique to the fetus) or inherited from either parent.  Abnormalities are divided into two categories: numerical and structural.3

Numerical abnormalities

Numeric refers to the fact that there are more chromosomes than expected; it Could be more or less. It is also called aneuploidy. Each scenario has a specific word:

Monosomy: One chromosome is missing from a pair.

Trisomy: There are three chromosomes instead of two.

Structural abnormalities

When the makeup of chromosomes presents a problem, it is known as a structural abnormality.  There are many ways in which structural abnormalities can occur.

Transfer: One piece of chromosome gets transferred to another. (This can be a Robertsonian translocation, where one chromosome attaches itself to another, or a reciprocal translocation, where the two chromosomes are traded.)

Deletion: A deleted or missing part of a chromosome.

Duplication: A chromosome is copied, resulting in additional genetic material.

Ring: A ring/circle is formed due to the rupture of a part of a chromosome.

Inversion: A piece of chromosome breaks off and turns upside down, then attaches itself to the parent structure.

Why do chromosomal abnormalities occur?

Chromosomal abnormalities are caused by cell division that does not go as planned. Specific cell division occurs either by mitosis or meiosis.

When a cell containing 46 chromosomes splits into two cells, it is called mitosis. New cells should also have 46 chromosomes each. The human body is made up of cells that are produced by mitosis. In meiosis, a cell also divides into two halves, but each of these halves contains 23 chromosomes. Meiosis produces sperm and eggs in the reproductive organs.

If mitosis or meiosis results in a different number of chromosomes than expected, it is considered a chromosomal disorder.