That is, they prevent the new human being from adhering to the wall of the womb and drawing nourishment.
Oral contraceptives have three mechanisms of action.
Two of the mechanisms are contraceptive in that their actions do not destroy human life. First, OC's often do prevent ovulation by suppressing a critical area of the hypothalamus, in the brain. Second, they cause changes in the cervical mucus, delaying movement of sperm, and sometimes preventing the sperm and egg ever uniting. The frequent failure of OC's to prevent conception is not their only aspect that is little known. Two significant events point to the very real danger of using OC's.