Birth defects: What they are and how they happen

Birth defects are problems that happen while a baby is growing during pregnancy. These problems can cause physical or mental disabilities, and in some cases, death. There are thousands of different birth defects. About 120,000 babies in the United States are born each year with a birth defect. The most common birth defects are heart defects, cleft lip and cleft palate, Down syndrome and spina bifida. While there's been lots of research, we still don't know the causes of some birth defects.

If a woman drinks alcohol during pregnancy, her baby may have a birth defect. Some illegal drugs and some prescription drugs can cause birth defects, too. Also, if a woman gets certain infections during pregnancy, such as cytomegalovirus or a sexually transmitted infection, her baby may develop a birth defect.

Some birth defects are causes by genetic factors. The baby could get something from his mother, his father, or both parents that can cause a defect. .

Certain birth defects affect a baby's body chemistry. These are called metabolic disorders. Phenylketonuria (PKU) is an example.

There are several steps you can take before and during pregnancy to help prevent birth defects. One important thing to do is have a medical checkup, or preconception visit, before getting pregnant.