Contraceptive Pill - Reproduction
About sixty million women in the world are currently using oral steroid contraceptives. These contraceptives usually consist of a synthetic estrogen combined with synthetic progesterone in the form of pills that are taken once each day for three weeks after the last day of menstrual period. This procedure causes an immediate increase in blood levels of ovarian steroids (from the pill), which is maintained for the normal duration of a monthly cycle. As a result of negative feedback inhibition of gonadotropins secretion ovulation never occurs. The entire cycle is like a false luteal phase, with high levels of progesterone, estrogen and low levels of gonadotropins.
Since the contraceptive pills contain ovarian steroid hormones, the endometrium proliferates and becomes secretory just as it does during a normal cycle. In order to prevent an abnormal growth of the endometrium, women stop taking the pill after three weeks. This causes estrogen and progesterone levels to fall, and permits menstruation to occur. The contraceptive pill is an extremely effective method of birth control, but it does have potentially serious side effects-including an increased incidence of thromboembolism, cardiovascular disorders, and endometrial and breast cancer. It has been pointed out, however, that the mortality risk of contraceptive pills is still much lower than the risk of death from the complications of pregnancy or from automobile accidents.