Differentiate between combination oral contraceptives (COCs) and progest in-only pills. Briefly ...

Combination oral contraceptives (COCs) are pills containing two hormonessynthetic estrogen and progestinthat play important roles in controlling ovulation and the menstrual cycle.COCs can be monophasic pills, which release a constant dose of estrogen and progestin throughout a woman's menstrual cycle, or multiphasic pills, which mimic normal hormonal fluctuations of the natural menstrual cycle by providing different levels of estrogen and progesterone at different times of the month.(Multiphasic pills reduce total hormonal dose and side effects.) Both monophasic and multiphasic pills block the release of hormones that would stimulate the process leading to ovulation. They also thicken and alter the cervical mucus, making it more hostile to sperm, and they make implantation of a fertilized egg in the uterine lining more difficult.

Progestin-only pills, also called mini pills, contain only a small amount of progestin and no estrogen. They work some what differently than combination pills. Women taking mini pills probably ovulate, at least occasionally.In those cycles, the pills prevent pregnancy by thickening cervical mucus, making it hard for sperm to penetrate, and by interfering with implantation of a fertilized egg.

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