A teratogen is anything that can disrupt a baby's healthy development during pregnancy. When a pregnant person is exposed, it can increase the risk of birth defects, growth problems, developmental delays, or long-term health issues.

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How serious the effects are depends on several factors - including when during pregnancy the exposure happens, how much of the teratogen is present, and the baby’s genetic vulnerability.

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Teratogens are generally grouped into the following categories. For clarity, we have separated medications from chemicals, since chemicals are more often encountered as environmental exposures.

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