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When in pregnancy do birth defects happen?


Updated January 16, 2005

Question: When in pregnancy do birth defects happen?
Answer: Birth defects happen before a baby is born. Inherited or genetic factors; things in the environment, such as smoking or drinking alcohol or not getting enough folic acid; and a woman's illness during pregnancy can cause birth defects. Most birth defects happen in the first 3 months of pregnancy, when the organs of the baby are forming. This is the most important stage of development. However, some birth defects happen later in pregnancy. During the last six months of pregnancy, the tissues and organs continue to grow and develop.

Some birth defects can be found before birth. If you want to know more about your risk of having a baby with a birth defect, contact a genetic counselor.

More About Birth Defects

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