Birth Defects: Causes, Risks, Diagnosis and Prevention

A birth defect is a problem that arises while a baby is developing in the mother's body, most often during the first 3 months of pregnancy. In the United States, one of every 33 babies is born with one.

Birth defects can change how the body looks, how it works, or both, and they range from mild to severe. Some, such as cleft lip or neural tube defects, are structural problems that are easy to see; others, such as heart disease, are found with special tests. How a defect affects a child's life depends mostly on the organ or body part involved and how severe it is.

Causes

The causes of some birth defects are known, but for many the exact cause is not. Researchers think most result from a complex mix of factors:

• Genetics. One or more genes may carry a change that stops them working properly, as in fragile X syndrome, or a gene or part of one may be missing.
• Chromosome problems. A chromosome or part of one may be missing, as in Turner syndrome, or there may be an extra one, as in Down syndrome.
• Exposure to medicines, chemicals or other toxic substances. Alcohol misuse, for example, can cause fetal alcohol spectrum disorders.
• Infections during pregnancy. Zika virus infection during pregnancy can cause a serious defect in the brain.
• Missing nutrients. Not getting enough folic acid before and during pregnancy is a key factor in neural tube defects.

Who is at higher risk

The chance of having a baby with a birth defect may be higher with:

• smoking, drinking alcohol or using certain "street" drugs during pregnancy;
• medical conditions such as obesity or uncontrolled diabetes before and during pregnancy;
• certain medicines;
• a family member with a birth defect; and
• being an older mother, typically over 34.

A genetic counselor can help assess an individual's risk.

Diagnosis

Some birth defects can be found during pregnancy through prenatal testing, which is one reason regular prenatal care matters. Others are found after birth, through newborn screening. Some, such as club foot, are obvious right away; others may not be discovered until later in life, when symptoms appear.

Treatment

Children with birth defects often need special care. Because the problems vary, so do the treatments, which may include surgery, medicines, assistive devices, physical therapy and speech therapy. Many children need several services and specialists, and their primary health care provider can coordinate that care.

Prevention

Not every birth defect can be prevented, but these steps before and during pregnancy improve the chance of a healthy baby:

• Start prenatal care as soon as you think you might be pregnant, and see your provider regularly.
• Get 400 micrograms of folic acid every day, ideally starting at least one month before becoming pregnant.
• Don't drink alcohol, smoke or use "street" drugs.
• Talk to your provider about any medicines you take or are considering, including over-the-counter medicines and dietary or herbal supplements.
• Learn how to prevent infections during pregnancy.
• Get any medical conditions under control before becoming pregnant.

Sources

• MedlinePlus, U.S. National Library of Medicine, "Birth Defects" (summary from the Centers for Disease Control and Prevention): https://medlineplus.gov/birthdefects.html