What the deceptive Mayo Clinic drug description below doesn't tell us is the "woman's egg" they refer to is FERTILIZED which means you ARE pregnant, so this drug DOES HARM existing pregnancies! Egg's don't develop in the womb that already happened in the ovary. But once the egg is fertilized in the womb it is a DEVELOPING embryo. Also it will "attach to the all of the uterus" only after it is fertilized! The first stages of a pregnancy.

"It works by preventing a WOMAN'S EGG from fully developing. It may also prevent the attachment of the WOMAN'S EGG to the wall of the uterus (womb)."
https://www.mayoclinic.org/drugs-supplements/levonorgestrel-oral-route/side-effects/drg-20074413?p=1