Of the non-genetic causes of birth defects, medications are a well-known offender. Early in the first trimester, many women don’t yet know that they are pregnant. This is a high-risk time to be taking certain medications as this is the major period of organogenesis or development of the organs.
While the science is very limited (pregnant women are generally not included in medication safety studies) there are a handful of medications that are considered category X drugs, or drugs that should not be taken in women who are or may become pregnant. See More