Birth defects are often detected prior to a baby's birth through advanced medical procedures: ultrasound, lab tests, prenatal screenings, and diagnostic tests. The doctor may increase the number and type of tests based on genetic history, the mother's health, or her age.

Your doctor may choose to conduct one or more ultrasounds during the course of your pregnancy. According to the U.S. Department of Health and Human Services website, an ultrasound is effective in detecting many of the major birth defects, including neural tube defects such as spina bifida and anencephaly. Certain blood tests are more effective in identifying Down syndrome.

Your doctor may order lab screenings or diagnostic tests that will indicate the risk of certain conditions. Diagnostic lab tests offer more specific information about whether or not the baby actually has a certain condition. Amniocentesis and chorionic villus sampling (CVS) are two of the most common diagnostic tests used during pregnancy.