"Plan B will NOT cause a miscarriage"
I think we can agree that an abortion is the same thing as causing a miscarriage?
The difference is that one is deliberate and one is unintentional.
Miscarriages are abortions; however, it is widely recognized that this happens and is usually not intended. An accidental homicide. Yes, a person is dead, but not usually because someone intended for him/her to die.
Abortions, the way we commonly think of them, is the deliberate act of snuffing out the embryo or fetus. Emergency contraception thus qualifies because the uterine lining is hostile to a fertilized ovum, and because that fertilized ovum cannot attach to the lining and develop, it is ejected from the body and dies.
This, of course, notwithstanding the controversy over other methods of artificial contraception.
Technically yes - abortion is short-hand for "abortion of pregnancy."
Pregnancy is a condition experienced by the mother, which begins at implantation within the uterine wall.
However, the life of the baby, or fetus if you prefer, begins at conception - when sperm fertilizes ovum.
So it is technically correct to say that preventing implantation does not cause abortion, since pregnancy has not yet occurred. It is just as correct to say that preventing implantation DOES intentionally snuff out the life of the child, which is what we pro-lifers are opposed to.