A: Despite remarkable advances in medical knowledge and technology, birth defects cannot be entirely prevented. Even with the best care, there's a small chance of having a baby with a problem.

On the other hand, there are many birth defects that can be prevented by optimizing your health before and during pregnancy. A preconception visit to your healthcare provider can identify factors in your personal or family medical history that could put you at risk for birth defects or inheritable genetic conditions. It also provides a chance to review current behavior and lifestyle factors that increase the risk for pregnancy problems.

If you already have a medical condition, such as diabetes or high blood pressure, a preconception visit is especially important. Women with poorly controlled diabetes, for example, have an elevated risk of delivering a baby with severe birth defects. Diabetic women who attain excellent sugar control prior to conception markedly reduce the risk of birth defects.

Certain infectious diseases, such as rubella or chicken pox, increase the risk of congenital problems. If you're not already immune to rubella (German measles) or chickenpox your doctor may advise you to obtain a vaccine prior to becoming pregnant. You'll need to postpone conception for at least one month after a vaccination, but you'll protect yourself from these risky infections during pregnancy.

Good nutrition is central to good pregnancy health. Folic acid, a B-vitamin, can prevent a birth defect called spina bifida. To lower the risk, women are advised to take a vitamin with at least 400 micrograms of folic acid for three months before they conceive and during early pregnancy. Women with a prior history of spina bifida should take a higher dose.

If you're already pregnant, remember that engaging in a healthy lifestyle is another way to increase your chances for a healthy baby. Eat a healthy diet and engage in exercise daily. Avoid smoking, alcohol and street drugs. Even secondhand smoke should be avoided. Some medications have been shown to increase the risk of birth defects. Discuss the use of all prescription and over-the-counter medications with your healthcare provider. Also find out if your work or hobbies expose you to potentially dangerous chemicals or to radiation.

By following the above guidelines, you'll be able to enhance your chances for delivery of a very healthy baby.