A large and growing number of tests are available to detect birth defects. Women who are considering becoming pregnant should consult with their obstetrician-gynecologist to find out what tests they should have and other steps they can take to reduce their risk of having a baby with birth defects, says Olga Tusheva, MD, an obstetrician-gynecologist with Highland Medical, P.C.
“Many birth defects are spontaneous, which means they are not caused by an underlying genetic mutation, and sometimes we don’t know why they occur,” Dr. Tusheva says. “Others are associated with genetic mutations or extra chromosomes, such as Down Syndrome.”
There are more than 4,000 types of birth defects. Some are minor and need no treatment, while others cause disabilities or require medical or surgical treatment. Some birth defects involve a part of the body that is missing or malformed, such as a heart defect, spina bifida, cleft palate, clubfoot, or a congenital dislocated hip.
Other types of birth defects involve the baby’s body chemistry. These are called metabolic birth defects. They include Tay-Sachs disease, which affects the central nervous system, and phenylketonuria (PKU), which affects the way the body processes protein.
Most babies with birth defects are born to parents without risk factors. However, the risk of birth defects is higher when certain factors are present. You are at increased risk if you:
- have a genetic disorder
- already have a child who has a genetic disorder
- have a family history of a genetic disorder
- belong to an ethnic group that has a high risk of certain genetic disorders
- are older
- use certain medicines around the time you become pregnant
- have a medical condition such as diabetes or obesity
- use recreational drugs or drink alcohol during pregnancy
There are three types of prenatal tests that can detect birth defects:
- Carrier tests can show if a person carries a gene for an inherited disorder, such as cystic fibrosis.
- Screening tests assess the risk that a baby will have Down syndrome and other chromosome problems, as well as major birth defects of the baby’s brain and spine called neural tube defects. These tests do not tell whether the fetus actually has these disorders.
- Diagnostic tests such as fetal DNA testing provide information about whether the fetus has a genetic condition.
“For women over age 35, we highly recommend fetal DNA testing, in which we extract the baby’s DNA from the mother’s blood as early as 10 weeks into pregnancy,” Dr. Tusheva says. “This testing can detect genetic mutations associated with Down Syndrome in as many as 99.9% of cases.” She adds, “The number of genetic mutations we test for is growing every year.”
Certain women are more likely to have babies with inherited disorders, which are caused by defective genes. Some inherited disorders are more common in certain races and ethnic groups, such as sickle cell disease (African American), cystic fibrosis (non-Hispanic white), and Tay–Sachs disease (Ashkenazi Jewish, Cajun, and French Canadian). “The doctor will go over a woman’s family history and ethnic background and determine the most appropriate screening tests for them to undergo,” Dr. Tusheva says.
All women considering becoming pregnant should take prenatal vitamins that contain folic acid, she recommends. Taking 400 micrograms of folic acid daily for at least one month before pregnancy and during pregnancy helps prevent neural tube defects. “Folic acid is essential for the normal formation of the nervous system. Lack of folic acid is associated with spina bifida and other malformations of the nervous system,” Dr. Tusheva says.
To reduce the risk of birth defects, it is important to avoid alcohol, smoking and taking drugs not prescribed by your doctor while you are pregnant, Dr. Tusheva emphasizes. “If you are taking prescribed medication, you should ask your doctor whether it may increase the risk of birth defects,” she says. “This is especially important in the first trimester, when the baby’s organs are developing. Even if you are taking a common medication that seems harmless, ask your doctor if it is safe to continue taking it during pregnancy.”