Hereditary Birth Defects

If you are thinking about becoming pregnant, it is important to be aware about the possibilities of having a child with a birth defect. Though discussing birth defects can be very upsetting, having the proper knowledge could help to prevent your baby from developing one. Many birth defects are actually hereditary in nature. This means that you or your partner could possibly pass along a genetic disorder. This article will outline some of the more common hereditary birth defects and ways that you can prevent passing them to your child.

What are Birth Defects?
Birth defects are defined as abnormalities of the structure or function of a baby at birth. Some birth defects can cause physical abnormalities, while others can cause mental or developmental delays. Birth defects can be passed on through a family or they can result from environmental hazards or certain infections. There are over 4,000 known birth defects and every year 150,000 babies in the United States are affected. Unfortunately, many birth defects cause emotional and physical hardship, and some can be fatal.

Hereditary Birth Defects
Hereditary birth defects are those disorders passed down to a child by its parents. Your baby has 46 chromosomes, which carry his genes and DNA. These chromosomes dictate what your baby will look like and how he will function. 23 of your baby�s chromosomes come from your egg, while the other 23 come from your partner�s sperm. However, if you or your partner has a defective or missing chromosome, a chromosomal abnormality could be passed on to your baby. This could result in a genetic birth defect. It is though that up to 20% of all birth defects are hereditary in nature.

How are Hereditary Birth Defects Passed Down?
There are a number of different ways that a hereditary birth defect can be passed on to your child. Some birth defects are passed on to a child by the mother, while others are passed along through the father. Some other disorders are passed on by both parents. There are three main ways of inheriting a birth defect:


    Dominant Inheritance:
    Some genetic defects are passed to a child through a process called dominant inheritance. This means that only one parent needs to have the genetic defect in order to pass it along to the child. Marfan Syndrome and Achondroplasia are dominant inheritance birth defects.


    Recessive Inheritance:
    Sometimes, both parents need to have a faulty gene in order for defects to be passed on to a child. This is referred to as recessive inheritance. Both Tays-Sachs disease and Cystic Fibrosis are recessively inherited birth defects.

    X-linked birth defects are passed from mothers to sons. This is because these genetic defects affect only the X-chromosome. Unlike girls, boys only have one X chromosome; if this X-chromosome is defective, the boy will be born with a genetic defect.

Common Hereditary Birth Defects
Some hereditary birth defects are more common than others. However, the chances of your child having a hereditary birth defect depends upon your own family history.


  • Tay-Sachs Disease: Tay-Sachs disease affects your baby�s central nervous system, causing seizures, blindness, and dementia. Common is Ashkenazi Jews, the disease is typically fatal. If both parents carry the defective gene, there is a 25% chance your baby will be born with the disease.
  • Muscular Dystrophy: Muscular dystrophy is a degenerative muscle disease that causes muscle weakness. Duchenne and Becker�s muscular dystrophy is inherited from the mother, with a 50% chance of a son developing the disease.
  • Sickle Cell Anemia: Sickle cell anemia is a disorder of the red blood cells, causing fatigue, pain, and other health complications. It is commonly found in people of African American and Latin American descent. Sickle cell anemia is a recessive disorder � if both parents carry the gene, there is a 25% chance of having a child with the disease.
  • Fragile X Syndrome: Fragile X syndrome can cause hyperactivity, mental development disorders, and autism. It typically affects more boys than girls, and causes the development of a long face, flat feet, and flexible joints. Fragile X is caused by a repeated DNA sequence, which can be passed down by the father or mother.

Diagnosing Hereditary Birth Defects
It is sometimes possible to diagnose hereditary birth defects before birth. Prenatal testing can successfully identify some genetic birth defects, including:


  • Down�s Syndrome
  • congenital heart defects


Babies are also screened for many of the more common birth defects, including Tay-Sachs and Sickle Cell anemia. Unfortunately, not all birth defects are tested for, so if you have a family history for a specific birth defect, be sure to ask for the proper testing. Some hereditary birth defects do not appear immediately after birth. Some can take up to 30 years (or more) to manifest. This can make diagnosis difficult and could prolong necessary treatment.

Preventing Hereditary Birth Defects
Hereditary birth defects can be prevented through knowledge and action.


    Know Your Medical History:
    Before you get pregnant, it is important to outline your own medical history as well as that of your partner. You should also inquire about the medical history of the rest of you family. Because hereditary disorders are passed down through families, you may be able to tell if your family is affected by a defective gene.


    See a Genetic Counselor:
    If you are at risk, speak with a genetic counselor. Genetic counselors are knowledgeable about various birth defects and how they are passed down. A genetic counselor will be able to assess your risk of having a baby with a genetic birth defect. She will also be able to make suggestions as to how you should proceed with pregnancy.


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