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Chromosomal Abnormalities and Miscarriage
In the world of fertility treatment, pregnancy and miscarriage are delicate topics. We strive to reach the end of the first trimester, so we can finally exhale ever so slightly after 12 weeks of carrying our eggs in one basket, literally.
But what happens if we don’t get there? What happens if we miscarry? The fact of the matter is, 1 in 5 pregnancies will end in miscarriage and more than 50% of those are due to chromosomal abnormalities. It is important to keep in mind that not all chromosomal abnormalities cause miscarriage.
Chromosomes are the genetic material inside the nucleus of each cell in the body. There are typically 46 chromosomes in a human cell which match up like puzzle pieces to form 2 pairs of 23. One pair is inherited from the mother and the other from the father.
However, the transition isn’t always a smooth one and there is room for error. Chromosomal abnormalities can be inherited or “de novo” which means they are new to the individual.
Structural abnormalities can occur as follows:
- Monosomy- full or partial deletion of one of the chromosomes in a pair. Turner Syndrome is an example of monosomy.
- Trisomy- full or partial duplication of one of the chromosomes in a pair, creating an excess of genetic material. Down Syndrome is an example of trisomy.
- Translocation- whole or part of one chromosome breaks off and is transferred to another chromosome. This can result in reciprocal translocation where two chromosomes exchange broken parts, or Robertsonian translocation where a full chromosome attaches to another complete pair. About 1 in 500 people will have a translocation.
In a reciprocal, or balanced, translocation there is no extra or missing genetic material. There are typically no outward signs of a balanced translocation.
In an unbalanced translocation, there is too much or too little genetic material. This may result is miscarriage or future disability in the child.
People with a balanced translocation are considered carriers and may pass the translocation to their children. Balanced translocation carriers may have children with an unbalanced translocation if the inherited chromosome has too much or too little genetic material.
- Inversion- part of the chromosome breaks off, inverts, and reattaches.
- Rings- part of a chromosome breaks off and forms a ring.
If you suspect chromosomal abnormalities in yourself or your partner or you have suffered multiple miscarriages, you should consider genetic testing.