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The Relationship Between Pregnancy Age and Chromosome Abnormality

written by: DulceCorazon•edited by: Leigh A. Zaykoski•updated: 6/13/2010

Increasing maternal age is one of the factors associated with the development of chromosome abnormality in a child. Find out more about the relationship between chromosome abnormality and pregnancy age of the mother.

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    When is the Right Age to Become Pregnant?

    Women’s fertility usually begins at the age 18 and reaches its peak at the age of 25, after which it gradually declines for the succeeding years until the age of 35, where the decline progresses rapidly. At 40, it is expected that women will have difficulty getting pregnant. However, all these statistics are just numbers. As soon as a woman starts menstruating and as long as the woman has not reached the menopausal stage, getting pregnant is possible.

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    What are Chromosomal Abnormalities?

    Chromosomes are structures in the nucleus of the cell that carries the genetic make-up of a person. There are 23 pairs of chromosomes in each cell and they are inherited from both parents. Of the 23 pairs, 22 pairs are autosomes which dictate most of the characteristics of a person. One pair contains the sex chromosomes, an X and a Y. Sex chromosomes determine the sex of an individual.

    About 50 percent of miscarriages are the result of chromosomal abnormalities. Chromosomal abnormalities occur when there is a mutation in one or two genes during the development of the fetus. Some chromosomal abnormalities are inherited from either one or both parents, while there are random mutations which can occur in children without the history of the disease in their families. Factors which may cause these mutations include age of the mother, radiation exposure during pregnancy, and other environmental influences.

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    What are the Common Chromosome Abnormalities Related to Late Pregnancy?

    Down syndrome, or trisomy 21, is a common chromosomal abnormality that has a strong link with maternal age. In Down syndrome, instead of having only two chromosome number 21, the baby has three of these chromosomes. The distinct features of Down syndrome are short limbs, small head, upward slant of the eyes and abnormally-shaped ears. Children with Down syndrome may also suffer from mental retardation and heart defects.

    The possibility of having a child with Down syndrome increases with maternal age. For a pregnant 20 year-old, the risk is 1 in every 1500 live births, while for a 35 year old, the risk is 1 in every 50. For a woman who gets pregnant after 40 years old, the risk 1 in every 50 births. The chances of having a child with Down syndrome or other genetic syndrome usually increase as the woman ages.

    Other genetic syndromes associated with increasing maternal age are Patau's syndrome and Edward's syndrome. These, however, are rare compared to Down syndrome.

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    What is the Relationship Between Chromosome Abnormality and Late Pregnancy?

    Maternal age is one of the factors contributing to the risk of having a child with chromosomal abnormality. At birth, women already have all the egg cells inside their body and as she ages, so do the eggs. Researchers believe that the genetic materials of the eggs also change over time. Because of these changes, the chances of having a child with genetic problems increases as women also advance in age. There are also studies that explore the link between genetic syndromes and the age of the father.