Q: Please explain to me what the primary Orthodox Jewish position is toward abortion. I have read that after 40 days (the period of completion) it is absolutely forbidden in any circumstances.
A: Abortion is totally forbidden even before the period of formation, which takes place 40 days from conception. The process of conception and pregnancy corresponds in Kabbalah to the three lower Divine worlds. Conception corresponds to the world of Creation. The 40-day period from conception corresponds to the world of Formation. Birth takes place after the subsequent period, which corresponds to the world of Action.
Early Kabbalah refers to three crucial moments in pregnancy: The moment of conception, the moment of formation and the moment of birth, which is the moment of the full development of the fetus in the womb. In Hebrew this moment is called Asiyah. It also means "completed being." The fetus is complete and now can be born into the world and continue to grow.
Above these three worlds, the union of the father and mother corresponds to the world of Atzilut, which is the level of Divine Consciousness, total and absolute unity. This gives birth to the three lower worlds. The union is expressive of Divine union. If the seed is properly conceived, then the Divine process of progeneration is taking place. It is absolutely forbidden to destroy this Divine process that actually begins from the moment of conception. This is the secret of creation, as it were, ex nihilo. These topics are discussed at length in the book, The Mystery of Marriage, which is to be published soon.
(note: This does not apply when the pregnancy threatens the life of the mother).