How are the forty days that permit abortion in cases of medical necessity calculated: Is it from the day of ovulation or from the time of menstruation?

There must be no leniency regarding abortion in the first forty days except under the conditions stipulated by the Fiqh Councils. Physicians begin calculating pregnancy from the first day of the last menstrual period before conception, but the true age of the fetus begins approximately 14 days after the end of that period, which is the ovulation period. This calculation is the basis for determining the forty days, the ensoulment, and the ruling concerning the blood discharged after an abortion.