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Chromosome Abnormalities & Pregnancy
Pregnancy is a period in a woman’s life where she carries an unborn offspring from the time of conception until the time of birth. A small number of these pregnancies may result in chromosome abnormalities. These are often inherited from the mother or from the father or even from both of them. Chromosome abnormalities may also occur even in children with no known family history of genetic disorders. These are usually due to random genetic mutations. Advancing age of the mother may also factor in the devlepment of some chromosome abnormalities. As a woman gets older, the chromosomes inside her eggs are also aging. Hence, the possibility that these gene-carrying structures have undergone changes is also high.
Chromosomes contain the genetic characteristics of an individual. When one undergoes a mutation or goes missing, or when there is the presence of an extra number, genetic syndromes usually occur. Some can present with mild to moderate disorders and the pregnancy may even reach full term. There are also severe chromosome abnormalities in pregnancy that usually lead to miscarriage or the termination of pregnancy especially during the first and second trimesters.
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Common Types of Chromosome Abnormality In Pregnancy
Common chromosomal abnormalities during pregnancy are as follows:
Down syndrome is the most common genetic disorder that causes mild to moderate developmental and intellectual disabilities. It is also referred to as trisomy 21 because of the presence of a third copy of chromosome number 21. Identifying features of the disorder are short stature, wide neck with excess skin and fats, short limbs, small ears and a single palmar crease in the hands.
Turner syndrome is a genetic abnormality affecting girls where, instead of having two X chromosomes, one of them is deleted or missing. Girls with Turner syndrome usually are shorter than average, have broader shoulders, and usually experience delayed sexual development.
Klinefelter syndrome is a chromosomal abnormality affecting boys. An extra X chromosome appears in their genetic make-up. Affected boys are often taller, less masculine, have less facial hair, larger breasts, broader hips and are less active compared with other boys.
Edward's syndrome is a rare chromosomal abnormality where an affected child has an extra chromosome 18. In every 3000 live births, 1 child may have the condition. Babies with Edward's syndrome, however, rarely survive after birth. Distinct facial features are small head, small wide-set eyes and small lower jaw. Serious medical conditions are also present, such as mental and growth retardation.
Patau syndrome is an uncommon disorder where there is an extra copy of chromosome 13. Distinct physical attributes are small head size, small eyes and cleft lip or palate. Another deformity usually seen is having extra hand or foot digits.
Aside from these, there are other chromosomal abnormalities that may occur. However, most of these often end up in miscarriage early in the pregnancy. Examples are Trisomy 8 and Trisomy 22.