Chromosome Abnormalities

Chromosome abnormalities are problems that exist in the genetic structure of a baby's chromosomes. Also referred to as chromosome disorders, these abnormalities can appear in different ways in your baby. Most chromosome abnormalities involve an extra copy of a particular chromosome. Sometimes chromosomes might be broken or arranged in the wrong order. Gene abnormalities, though rare, also occur, especially if the parent also has that gene abnormality.

How They Affect Your Baby
Abnormal chromosomes are caused by a problem in the development of the sperm or egg cell. No one really knows what causes these problems, but chromosomal abnormalities due seem to appear more frequently as a mother ages.

Typically, chromosomal abnormalities cause abnormal phsycial appearance though they can also cause delayed mental development. The effects of the chromosomal abnormality depends upon what actually went wrong with baby's chromosomes.

Get the facts about chromosome abnormalities.

There are no cures for chromosomal abnormlities but treatments are available to those suffering from them. Many of these treatments allow the patient to live a happier life. However, most baby's with a chromosal abnormality will be miscarried early on in the pregnancy. In fact, about 70% of miscarriages in the first trimester are thought to be the result of chromosomal abnormalities.

Tests are now available to check whether or not your baby may be born with a chromosomal abnormality. These tests are called chromosomal screens and may indicate whether a couple is more likely to have a baby with a chromosomal disorder. These tests do pose a slight risk of miscarriage, though.

What is a Chromosome?
Chromosomes are made up of DNA, the building blocks of life. Chromosomes are almost like strings, and they contain every piece of information about our genetic makeup.

Everybody has 23 pairs of chromosomes, or 46 chromosomes in total. Each pair is inherited from your parents - one from your mother and one from your father. Two of your chromosomes are responsible for determining what sex you are - for males the sex chromosome is XY and for females it is XX.

What are Genes?
Every one of our chromosomes is filled with thousands of gene pairs. Genes contain information like the color of our hair, the color of our eyes, our weight and our height. Genes are also responsible for our traits and behaviors.

Am I at Risk?
It is important to know if your baby is at risk for a chromosomal abnormality. Risk level seems to depend upon your age - the older you are, the more chance you have of delivering a baby with a chromosomal abnormality.

Maternal Age

< Risk of chromosomal abnormality

Risk of Down’s Syndrome
















These statistics only take into account live births.  Most chromosomal abnormalities result in miscarriages early in the pregnancy.

If you have already had a child affected by a chromosomal abnormality, you are at increased risk for passing along another chromosomal abnormality.

What Different Disorders are There?
There are a variety of different chromosomal disorders, depending upon what is actually wrong with the chromosome. A very common abnormality is trisomy. A trisomy occurs when a baby has 3 copies of a chromosome instead of just two. A trisomy abnormality can bring on Downs syndrome, Patau’s syndrome, and Edward’s syndrome

Sometimes a baby will be born without the second sex chromosome (has chromosomes 45X0 in stead of 46XX or 46XY). This baby will be a girl and suffer from Turner’s syndrome.  Other babies are born with too many X chromosomes, resulting in Klinefelter syndrome.

Molar pregnancies occur when abnormal chromosomes prevent a proper pregnancy. Instead of an embryo forming, a strange mass will begin to grow in the uterus.

A Place to Begin
Where do you start when you find out your child has a chromosomal abnormality?  Pour over all the research you can get your hands on and speak with other parents.  If there is a history of chromosomal abnormalities in your family or in your partner’s family, you will be referred to a genetic counselor.

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Does your baby have chromosomal abnormalties? Visit our Pregnancy Complications forum to speak with other women.


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i was so nervous about having a baby with some sort of syndrome like down\'s but i wasn\'t sure if i wanted to have that test where they take some of the fluid so i did all these blood tests and ultrasounds instead and they said based on the results of these tests combined the chances of me having a baby with downs syndrome would be something like 1 in 18,000 so that made me feel much better and none of the tests for checking were intrusive.
4 years ago