An embryo has no rights. Rights do not pertain to a potential, only to an actual being. A child cannot acquire any rights until it is born. The living take precedence over the not-yet-living (or the unborn).
Abortion is a moral right—which should be left to the sole discretion of the woman involved; morally, nothing other than her wish in the matter is to be considered. Who can conceivably have the right to dictate to her what disposition she is to make of the functions of her own body?