http://www.cdc.gov/ncbddd/bd/faq1.htm
National Center on Birth Defects and Developmental Disabilities
A birth defect is a problem that happens while the baby is developing in the mother’s body. Most birth defects happen during the first 3 months of pregnancy. This page presents frequently asked questions about birth defects, including information on most common birth defects and role of genetic factors in causing birth defects.