what are substances that cause birth defects?
Besides the known risks, there lurks a vast gray area in which the research is inconclusive. According to the March of Dimes web site, the cause of about 70% of birth defects is unknown. And most known defects are due to genetic or other unpreventable causes -- not to mom's exposure to toxic chemicals, foods, drugs, or infections. So is there any way to lower the risk? The following information should help you separate the facts from the likely fiction. Known Risks . Substances that can cause birth defects are called teratogens. Exposure to them does not automatically put your fetus at risk. The level and length of time of exposure, as well as the stage of the pregnancy at time of exposure, can come into play.