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Birth Control Pills : Oral contraceptives (OCs) are medications that prevent pregnancy. They are one type of birth control. OCs may contain combinations of estrogen and progestin or progestin alone. Combinations of estrogen and progestin prevent pregnancy by inhibiting the release of the hormones LH and FSH from the pituitary gland in the brain. LH and FSH play key roles in the development of the egg and preparation of the lining of the uterus for implantation of the embryo. Progestin also makes the uterine mucus that surrounds the egg more difficult for sperm to penetrate and, therefore, for fertilization to take place. In some women, progestin inhibits ovulation (release of the egg). The combination OCs are called "monophasic," "biphasic," or "triphasic." Monophasic OCs deliver the same amount of estrogen and progestin every day. Biphasic OCs deliver the same amount of estrogen every day for the first 21 days of the cycle. During the first half of the cycle, the progestin/estrogen ratio is lower to allow the endometrium to thicken as it normally does. During the second half of the cycle, the progestin/estrogen ratio is higher to allow normal shedding of the lining of the uterus to occur. The triphasic OCs have constant or changing estrogen concentrations and varying progestin concentrations throughout the cycle. There is no evidence that bi- or tri-phasic OCs are superior to monophasic OCs, or vice-versa. OCs are prescribed for the prevention of pregnancy. When taken as directed, OCs fail in less than 1 in every 200 users over the first year of use. OCs also are prescribed to treat mid-cycle pain which some women experience with ovulation. OCs, while regulating the menstrual cycle, reduce menstrual cramps and heavy bleeding, and, because of the reduced bleeding, they may prevent the anemia that can develop in some women. Doctors sometimes prescribe higher doses of OCs for use as "morning after" pills to be taken up to 72 hours after unprotected intercourse to prevent fertilization and pregnancy. |
20th August 2008