Which of the following mechanisms best explains the contraceptive effect of bih control pills that contain both synthetic estrogen and progestin?
The primary effect is to suppress gonadotropins at the time of the midcycle LH surge, thus inhibiting ovulation. The prolonged progestational effect also causes thickening of the cervical mucus and atrophic changes of the endometrium, thus impairing sperm penetrability and ovum implantation, respectively. Thus, the Progestational agents in oral contraceptives work by a negative feedback mechanism to inhibit the secretion of LH and, as a result, prevent ovulation. They also cause decidualization and atrophy of the endometrium, thereby making implantation impossible. Progestins do not prevent irregular bleeding. Estrogen in bih control pills enhances the negative feedback of the progestins and stabilizes the endometrium to prevent irregular menses.
Direct inhibition of oocyte maturation
Inhibition of ovulation
Production of uterine secretions that are toxic to developing embryos
Impairment of implantation hyperplastic changes of the endometrium
Contraceptives