Answer:
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.