Environmental substances that can contribute to birth defects include alcohol, certain drugs/medications and infections. Women who drink heavily during pregnancy are at risk of having a baby with a pattern of mental and physical birth defects called fetal alcohol syndrome. Because even moderate or light drinking may harm a baby, women who are pregnant or planning pregnancy should not drink any alcohol. They also should avoid illegal drugs such as cocaine and Ecstasy, and ask their health care provider about the safety of any prescription and over-the-counter medications they take. Women also can take steps to help prevent certain infections such as toxoplasmosis
that can cause birth defects.