Aristoteles held that the embryo had a basic soul from conception on, but only received the full version on day 40 for males, 90 for females. Which is terribly sexist customer service. Apparently the 90 days made their way into Christianity when someone (Thomas of Aquin?) amalgamated the Septuaginta with Greek philosophy (Ex 21,22 of course considers the fruit of the womb something else but life, as accidentally aborting it is to be punished by another principle than the "a life for a life" one established in the subsequent verses). When capital punishment for abortion was abolished in Prussia under Frederick the Great, the three-month-distinction nevertheless was continued. It's interesting how ancient traditions continue in modern law; or the ancients got it right already, depending on your view.