A teratogen is a(n): Group of answer choices fertilized egg that undergoes rapid cell division. unborn child with one or more physical defects or abnormalities. chromosomal abnormality. substance that can cross the placental barrier and harm an unborn child.

SUBSTANCE THAT CAN CROSS THE PLACENTA BARRIER AND AN THE UNBORN CHILD.

Explanation:

In an embryo, any substance that can cause its irregular growth or harm is called teratogens. These substances affect the development of the embryo or fetus. It can also cause birth defects in a child. Teratogens can be radiations, drugs, chemicals and other harmful substances. They have the ability to cross the placenta barrier and harm the embryo.