My neighbor is five months pregnant and still smoking a pack of cigarettes every day. Perhaps she is unaware that nicotine is a(n) for the fetus of a mother who smokes heavily.

Teratogen

Explanation:

Teratogen -

It is the cause of danger to the life of he fetus , and can even damage the body of the women and the embryo , is referred to as the Teratogen .

Hence , from the question ,

Smoking even during the stage of pregnancy , can cause harm to the unborn life , as the mother smokes very heavily .

Hence , from the given scenario of the question ,

The correct answer is Teratogen .

you get into a car crash and die