Chromosomal abnormalities are a random occurrence, but very common in women over 35 years. Chromosomal abnormalities occur due to various reasons out of which only 5% are genetic.
An abnormal sperm, abnormal egg, an improper fertilization and exposure to toxic environmental factors can be a potent cause of chromosomal abnormalities. There are two types of chromosomal abnormalities that result in miscarriages.
Embryo Chromosomal Abnormalities
Majority of miscarriages are an outcome of unnaturalness of a number of chromosomes in the embryo. Sometimes, embryos have a pair of chromosomes that are either more than or less than 23 (actual no.) thus, becoming vulnerable to miscarriage. Due to chromosomal abnormalities, the embryo may not be able to develop properly and its survival in the womb may end. Sadly, there is no treatment preventing the development of chromosomal abnormalities in the embryo. It is not necessary that all embryos with chromosomal unnaturalness will end up in miscarriage. Few can reach delivery, but such babies are born with some birth defects. Types of chromosomal abnormalities in embryos include:
- Nullisomy: It occurs when an embryo is missing a pair of chromosome. Nullisomic embryos do not survive thereby, ending in miscarriages.
- Monosomy: This occurs when one chromosome of the foetus lacks its homolog. Monosomies do not survive and if at all they do survive, they have a number of birth defects such as Down syndrome or do not live for longer than a few days or weeks.
- Trisomy: This occurs when one extra copy of a chromosome is present in the foetus. Trisomies have few chances of survival. Most trisomies are born with Down syndrome. They have distinct facial features, altered body shape and short stature.
- Tetrasomy: It is a rare case and occurs when a total of four chromosome pairs are present.
In pregnancy through IVF process, chromosomal abnormalities can be identified using pre-implantation genetic diagnosis. No matter what the cause is, a miscarriage is always painful and emotionally devastating.
Parental Chromosomal Abnormalities
Miscarriages due to parental chromosomal unnaturalness are rare. In this form of abnormality, one of the parents has some abnormality in his/her chromosomes. Also known as translocation abnormality, the chromosome of any parent (say chromosome 15) changes or swaps its place with another chromosome (say chromosome 23). Such parents can have a completely normal baby. A baby born with same chromosomal pattern or a foetus with chromosomal abnormalities will result in miscarriage.
Nothing can be done to prevent chromosomal abnormalities in your embryos, but to alleviate the chances of miscarriage due to chromosomal unnaturalness, take the adequate nutrition. Consult your doctor to increase the consumption of folic acid, which is helpful in preventing chromosomal abnormalities.
Recurrent Miscarriage and Chromosomal Abnormalities
According to the Oxford Journal, Human Reproduction, “Chromosomal abnormalities are an important cause of spontaneous abortion and recurrent miscarriage (RM).” Genetic problems in an embryo increase the chances of repeated miscarriage by 3 per cent to 5 per cent. The pregnancy naturally terminates in its early stages. According to the Textbook of Gynaecology by Kamini A Rao, chromosomal abnormalities are the direct cause of spontaneous abortion and autosomal trisomy, polypliodi and monosomy X are most commonly found abnormality in cases of recurrent miscarriage.
Maternal Age and Chromosomal Abnormalities
The Advanced Fertility Center of Chicago states that, “We do not know exactly why there is an increase in chromosomal abnormalities in the eggs of women as they age. However, research studies have clarified some of the issues involved. The meiotic spindle is a critical component of eggs that is involved in organizing the chromosome pairs so that a proper division of the pairs can occur as the egg is developing. An abnormal spindle can predispose to development of chromosomally abnormal eggs.”
The older women have more chances of having abnormal functioning of chromosome spindles and therefore, are at an increased risk of developing embryo chromosomal abnormalities/problems.
Testing for Chromosomal Abnormalities
Couples who have had recurrent miscarriages are advised to undergo chromosomal abnormalities to determine the genetic fault in the parents or in the foetus. Foetus’s genetic makeup can be traced using Chromosome Testing on Foetal (Miscarriage) Tissue and parents’ genetic pattern can be tested using Karyotyping of Parents.
Chromosome Testing on Foetal (Miscarriage) Tissue: This test is conducted immediately after the miscarriage has happened. The genetic pattern of the foetus is studied deeply to determine any chromosomal abnormality it had which inhibited its survival in the womb.
Karyotyping of Parents: The chromosomal pattern of blood of both the parents are analysed to determine any genetic problem in the either of them. For better understanding of chromosomal anomaly that caused miscarriage, parents’ genetic pattern is studied in conjunction with foetus’s makeup.
Chromosomal abnormalities are among the key causes of miscarriage in the first trimester of pregnancy and unfortunately, these cannot be controlled.
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