Birth Defects

Reviewed by James Brann, MD

Reducing the Risk of Birth Defects

Also called a congenital disorder, there are more than 4,000 types of known birth defects, all ranging from mild defects to severe ones. Present at birth, a birth defect will affect how your child functions, looks, or possibly both.
For instance, a birth defect such as clubfoot, or too many toes and fingers, is obvious as soon as a baby is delivered. Other defects, however, like hearing loss and heart defects, may need special tests to uncover. Still, some birth defects are present, but may not be noticed until later.

The cause of birth defects

Sometimes a birth defect may be inherited. For instance, an error in chromosomes or genes may be something a parent passes down to their child. In other cases, a birth defect is caused by something harmful a fetus is exposed to. This may include infections, medications or chemicals. The harm is likely dependent on how much a pregnant woman and her child are exposed to, at what point it happened during pregnancy, and the length of exposure. In other cases, a number of different factors contribute to the problem. Still for many cases, it’s difficult to figure out an exact cause.

The risk of birth defects

Some women are at greater risk than others are, though, in having a child with a birth defect. Risk factors include:
  • Personal history or family history of birth defects
  • You are 35 or older at the time your baby is full-term
  • You used certain medications about the time you conceived
  • You gave birth to another child with a birth defect
  • You drink alcohol or use illegal drugs
  • You have diabetes


While a majority of birth defects happen with no family history of problems, you may want to consider testing or counseling if you do have a family or personal history of birth defects.

Vitamin supplements and birth defects

One of the most recommended things a pregnant woman can take in helping to prevent certain defects is folic acid, a type of B vitamin. Folic acid helps to prevent neural tube defects. To be most effective, though, you need to take it well in advance of getting pregnant and then through the first trimester.

When it comes to vitamin A, you need to watch how much you take. Severe birth defects have been linked to extremely high levels of vitamin A. When it comes to your prenatal multivitamin, make sure it doesn’t have more than 5,000 international units of vitamin A. In the case of certain supplements, you may find way too much. Some have 25,000 international units in just one does.

Obesity and birth defects

What about obesity? In medical terms, obesity means you have a body mass index, or BMI, of 30 or more. If you’re obese before you become pregnant, you already have a higher risk of having a baby born with birth defects. The most common types of obesity-related defects include heart defects, abdominal wall defects and neural tube defects. There’s another problem with obesity, too. It’s harder to spot fetal defects during an ultrasound with an obese mother. In addition, there are also links between obesity and gestational diabetes, infections, cesarean deliveries and preeclampsia.

Medical conditions and birth defects

It’s important to see your doctor before becoming pregnant if you have any type of medical condition. You’ll want to find out what you need to do in terms of medication, diet, or simply controlling your condition before trying to get pregnant. A diabetic has a high level of glucose, or sugar, in their blood. Having too much glucose can do damage to a mother’s organs, and her baby. It’s possible to keep your glucose in check with exercise, medication, and diet before getting pregnant so that you can help lower the risk of having a child with a birth defect.

Alcohol and birth defects

Alcohol is not a good idea during pregnancy. This is because using alcohol while you’re pregnant is the leading cause of birth defects including mental retardation. Fetal alcohol syndrome is among the most serious. Pregnant women need to avoid alcohol because it’s not clear how much alcohol is safe during pregnancy, if any at all.

Smoking and pregnancy

As far as smoking, it’s linked to a number of problems during pregnancy including premature rupture of membranes and problems with the placenta. A child delivered by a woman who smoked while pregnant is also a risk of developmental problems, hospitalization and sudden infant death syndrome. Secondhand smoke is risky, too. Exposure may be harmful before delivery, and to a newborn.

Illegal drugs and birth defects

Illegal drugs may cause a number of problems during pregnancy, too, including growth problems, long-term behavioral, emotional and learning problems, or even brain injury. Many of these types of drugs can increase the chance of serious birth problems including preterm birth. This is why it’s so important to both a mother and her baby to avoid illegal drugs both before and during a pregnancy.

Over-the-counter/prescription drugs and birth defects

Certain medications are also responsible for birth defects. If you’re trying to get pregnant, or you are pregnant, make sure you tell your medical provider. This means not only the doctor who prescribes the drugs to you, but also your dentist, mental health provider, or any other doctor or nurse you see for something non-pregnancy related. If you already have a prescription drug you’re taking, don’t stop until you talk to your doctor about it. Do, however, check with your doctor before you take any type of over-the-counter drug. This includes cold and allergy remedies, herbal products, vitamins, skin treatments, laxatives and pain relievers.

Infections and birth defects

There are certain types of infections, such as rubella, that may increase the risk of birth defects. Also called the German measles, this infection may lead to mental retardation, blindness, deafness or heart defects in your child. While there’s a vaccine for rubella, you can’t be vaccinated against it when you’re pregnant.

Another infection comes from eating undercooked or raw meat, eating unwashed vegetables or coming in contact with animal feces, especially cats. Toxoplasmosis is actually caused by a parasite in the soil, and it is transmitted to people in these ways. Toxoplasmosis may cause birth defects including vision problems, hearing loss and mental retardation. To protect yourself, only eat well-cooked meat. Also, wear gloves if you garden and while holding unwashed vegetables. If your outdoor cat uses a litter box, make sure someone else is emptying it. If this isn’t possible, make sure you are wearing gloves, and thoroughly wash your hands when you’re finished.

Additionally, sexually transmitted diseases, or STDs, can also cause some serious birth defects. Herpes or syphilis may lead to infant problems including death or blindness.

The most common type of viral infection for newborns is cytomegalovirus, or CMV. While most of the time CMV infections don’t cause significant problems, it may lead to vision loss, deafness or retardation in severe cases.

Environment and birth defects

Other birth defects may be tied to exposure from toxic agents including radiation, mercury or lead. Sometimes women find themselves exposed to things like this while working. In other situations, it is at home. Still, sometimes it’s the food supply. Some harmful agents aren’t even known.

What about fish?

That brings us to the question of fish. You need to avoid eating certain types of fish while you’re pregnant due to the high levels of mercury. While mercury is a natural substance, it builds up in some fish. If you eat large amounts of the fish, it can harm a pregnant woman and her child. You’ll want to avoid things like swordfish, shark, tilefish and king mackerel.

Additionally, you’ll want to limit other types of fish. Pregnant women shouldn’t eat more than 12 ounces of fish per week that are low in mercury. That’s about two meals of things like canned light tuna, Pollock, shrimp, catfish and salmon. As for tuna steaks and Albacore tuna, or white tuna, the mercury levels are higher. For these types of fish it’s advised a pregnant woman only eats six ounces or less per week.


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