Birth Defects

Birth defects are one of the things women worry about the most during pregnancy. While there is an increased risk for women who are over age 35 of delivering a baby with birth defects, these risks are not overwhelming. Many problems can be diagnosed during pregnancy using screening tests.

Chromosomal Abnormalities

Women over 35 years of age are at increased risk for having babies with chromosome problems. The primary point to remember is that while these risks are elevated, the odds are that you will have a healthy baby because only 3 percent of all babies are born with birth defects. Understanding these risks can help you make decisions about prenatal tests.

Chromosome problems are referred to as trisomies since they are associated with an extra chromosome of a specific pair. For example, a baby with Down syndrome has a total of 47 chromosomes instead of the usual 46; in this case, there are three number 21 chromosomes instead of two; hence, the term trisomy 21.

Women over 35 are at risk for several trisomies, including trisomy 21, trisomy 31, and trisomy 18, as well as having babies with extra sex chromosomes. For example, instead of XX (girl) or XY (boy), one could have XXY, a special type of trisomy called Klinefelter's syndrome.

Babies with trisomy 13 and 18 have a high mortality rate, with 90 percent having died from their disorder by one year of life; survivors are usually profoundly handicapped and often have multiple birth defects. More than half of the children with trisomies born to women over 35 will be Down syndrome babies.

Down Syndrome

Down syndrome is a chromosomal abnormality in the trisomy category, which means the child is born with three copies of a certain chromosome instead of the normal two. Children with this disorder are born with an extra 21st chromosome. This occurs in one out of every 733 births.

The risk of Down syndrome increases with the mother's age. At age 30, the risk is one in 1,000. At age 35, the risk is one in 400. At age 40, the risk is one in 100. Interestingly, even though older moms have a higher risk of Down, 80 percent of Down babies are actually born to women under age 35; this is simply because there are more women having babies under 35. Once you have a baby with Down syndrome, your risk of having another is about one in 100.

For information and support about Down syndrome, contact the National Down Syndrome Society.

Down syndrome is associated with a heart defect (50 percent of Down babies have this) and hearing and vision difficulties. These children have an identifiable look, with eyes that slant up and ears that fold over. They often have short necks, small noses, and small hands. Mental retardation can range from mild to serious.

Down syndrome, as well as trisomy 13 and 18, can be detected during pregnancy through a combination blood test and ultrasound, or through amniocentesis or chorionic villus sampling (CVS). Recent studies have shown that women who have had a Down syndrome baby do not process folic acid normally, but studies into the causes of Down syndrome are ongoing.

Other Birth Defects

There are a wide range of birth defects, some of which are chromosomal and some of which are not. In general, older women are more at risk for all types of birth defects, but the increase in risk is small. Women ages 35 to 39 have an increased risk of 1.4 and women over 40 have an increased risk of 1.7 of having a baby with a congenital birth defect of any kind.

Again, it is important to remember that this is relative risk; a younger woman has a risk of 1 percent (1 in 100) of having a baby with a birth defect. If you are 39, your risk is 1.4 times that, or 1.4 percent (14 in 1000). There is not an identifiable increase in any specific birth defect, though, just a slightly increased risk of any birth defect.

Most birth defects can be identified during pregnancy through screening methods available today. Some birth defects are minor. Some can be corrected after birth, while others are serious or life threatening.

Coping with a Diagnosis

Learning that your baby has or may have a birth defect can be devastating. It is often difficult to know what to do or where to turn. Get as much information as you can from your health-care provider and genetic counselor. Get details about how severe the defect is or is thought to be. Learn about the implications of the birth defect.

Take some time to consider what you want to do. What kind of life would this child have? What would your life be like as the parent of a child in this situation? Are you able to cope with this defect? How would you cope? Contact the associations that are set up to support parents of babies with specific birth defects for information about support and education that is available to you.

If you are considering terminating the pregnancy, ask questions about that procedure, your risk of having another baby with a similar defect, and your chances of conceiving again.

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