A zygote on its own has zero chance of surviving and therefore has no life to speak of. It has to implant itself in uterine endometrium (zygote at this stage is now called blastocyst) to have a chance to survive. This is the reason why the American Medical Association (AMA), American College of Obstetricians and Gynecologists (ACOG), British Medical Association (BMA) and other equivalent medical authorities in other countries define blastocyst as the beginning of life (conception) and not zygote.
Hormonal birth pills prevents zygote and/or blastocyst formation. IUD is spermicidal and/or ovicidal. None of them kills a blastocyst that is already formed and therefore are NOT abortifacient.
Dr. Wilfredo Garcia
New Orleans, USA