Final answer:
Oral contraceptives are effective because they prevent ovulation by maintaining constant levels of hormones, which inhibit FSH and LH release, thus preventing egg maturation and release.
Step-by-step explanation:
Oral contraceptive pills work by delivering daily synthetic progestins to a woman’s reproductive system. This is an effective method of birth control because it inhibits ovulation by maintaining constant hormone levels. The presence of constant levels of estrogen and progestin provides negative feedback to the hypothalamus and pituitary gland, which in turn prevents the release of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). Without FSH and LH, ovarian follicles do not mature and the LH surge, which triggers ovulation, does not occur. Moreover, oral contraceptives also cause changes in the uterine lining, making it less favorable for implantation, and thicken the cervical mucus to prevent sperm from reaching any eggs that may have been released.