Understanding Risk of Birth Defects and Genetic Conditions

Planning a pregnancy is an exciting experience, but it may also come with worries about how to keep you and your baby as healthy as possible. You may be thinking about congenital anomalies—also known as birth defects—which may be present when a baby doesn’t develop in the usual way.

“‘Birth defects’ refer to conditions in any area of a baby which did not follow the usual path of development—it does not mean the condition occurred at birth,” says Louise E. Wilkins-Haug, MD, PhD, a Mass General Brigham obstetrician-gynecologist. “Birth defects happen for many different reasons. There are steps you can take before and during pregnancy to help reduce risk.”

Dr. Wilkins-Haug cares for patients and is medical director of the Fetal Therapy Program at Brigham and Women’s Hospital, which offers advanced treatments for certain conditions found before a baby is born. She explains more about what causes birth defects and what you can do with the help of your health care team to prepare for a healthy pregnancy—and healthy baby.

What causes birth defects (congenital anomalies)?

Birth defects occur because of different reasons, and for many, the cause isn’t known. It may also be a combination of different factors.

Birth defects (also called congenital anomalies) are structural changes in the development of the baby, which are present at birth. They aren’t caused by the birth process itself. Birth defects may affect how the body looks, works, or both. They can impact any part of the body, such as the brain or heart.

“I want to be clear that having a birth defect doesn’t mean a baby is ‘defective.’ This is a medical term that describes certain health conditions that develop in a baby during pregnancy,” says Dr. Wilkins-Haug. “Some are mild, and others are more severe.”

What increases risk of birth defects and genetic conditions?

Certain factors increase the chance that an infant will have a birth defect or genetic condition, such as:

• Genetics. Parents pass down genes—the “instruction manual” for how each person grows and functions throughout life—to their children. Some genetic changes may make certain birth defects more likely. These include conditions like Down syndrome and spinal muscular atrophy.
• Having a family history of birth defects
• Exposure to substances during pregnancy, like alcohol, nicotine, illicit drugs, and some medications
• Having certain medical conditions or infections during pregnancy
• Environmental factors

Can you prevent birth defects?

Not all birth defects can be prevented, but there are steps you can take before and during pregnancy to help reduce risk.

When planning a pregnancy, talking with your health care provider is an important step. Tell your primary care provider (PCP) you’re planning to get pregnant. They may refer you to an obstetrician-gynecologist (OB/GYN), and they can help you prepare for a healthy pregnancy.

Here are some steps you can take before and during pregnancy to help prevent birth defects:

• Meet with your PCP or OB/GYN before getting pregnant. They can answer any questions you may have about your health and medications, order any special tests you may need, or suggest lifestyle changes you can make to help reduce your risk of having a baby with a birth defect.
• Take folic acid and other prenatal vitamins. Daily multivitamins containing vitamins A, C, and D, folic acid, and minerals like iron help lower the risk of birth defects when taken before and during pregnancy.
• Get existing medical conditions under control. Chronic conditions like diabetes and obesity are associated with an increased risk of having an infant with a birth defect. Optimizing glucose (blood sugar) management and weight loss before pregnancy can significantly lower this concern. Work with your health care team to manage any existing conditions before you get pregnant, and partner with them to stay as healthy as possible throughout your pregnancy.
• Talk to your provider about medications you take. Ask them before starting or stopping any medication before or during pregnancy to make sure it’s safe. Certain medications may increase the risk of having a birth defect. For example, the acne drug isotretinoin increases the risk of birth defects. If you take a medicine that may be harmful for your baby, your provider may change it to one that’s safer before or during pregnancy. But some medicines may be really important to your own health, even if they may affect your baby. You and your provider can weigh the benefits and risks of medicine.
• Don’t use certain substances. Drinking alcohol and using marijuana, nicotine products (such as smoking cigarettes or vapes), or illicit drugs like opioids during pregnancy can harm your baby and increase risk of birth defects. Talk to your health care provider if you want help quitting or use other resources, like Alcoholics Anonymous or calling 1-800-QUIT-NOW.
• Maintain a healthy weight. You can work with a provider before or during pregnancy to manage your weight.
• Treat fevers and avoid overheating. Treat any fevers over 101 degrees, and avoid environments where you may overheat, like hot tubs.
• Prevent infections. Certain infections, like rubella (measles) or sexually transmitted infections (STIs), increase the risk of your baby developing certain conditions during pregnancy. Getting recommended vaccines can help prevent infection, and screening tests (like those for STIs) can help providers catch and treat infection early.
• Get recommended vaccinations before and during pregnancy. Talk to your provider about staying up to date on your vaccines.

What does folic acid do?

Folic acid is a B vitamin that helps your body make new cells.

Having enough folic acid in your body before and during pregnancy helps prevent certain birth defects that affect the brain and spine, called neural tube defects (NTDs). The Centers for Disease Control and Prevention (CDC) recommends getting 400 mcg of folic acid every day, even if you’re not planning to get pregnant. You can take supplements or eat certain foods, like leafy greens, beans, or oranges, to get enough folic acid in your diet.

Screening and treatments for birth defects or genetic conditions

Screening tests during pregnancy help show how likely your baby is to have certain birth defects or genetic conditions. These include blood tests and ultrasound exams.

Sometimes, a screening test raises a concern about an abnormality, but the baby may not have a birth defect. Your provider orders a diagnostic test to be sure. Providers can diagnose some birth defects during pregnancy, while others aren’t found until after the baby is born.

If your baby is diagnosed with a health condition before birth, fetal therapy—where doctors treat your baby while it’s still inside you, or “in utero”—may be an option. These treatments range from the pregnant person taking medication, to doctors treating the baby through the umbilical cord or with surgery in utero for some birth defects. 

“We’ll work closely with you through each step, from diagnosis to treatment to specialized care after birth,” says Dr. Wilkins-Haug. “We listen to your concerns and do whatever we can to keep you and your baby as healthy as possible.”