Polycystic ovarian syndrome, or PCOS, is a condition in which a woman’s levels of the sex hormones estrogen and progesterone are out of balance. This leads to the growth of ovarian cysts (benign masses on the ovaries). PCOS can cause problems with a women’s menstrual cycle, fertility, cardiac function, and appearance. Irregular periods is the most common characteristic. Examples include menstrual intervals longer than 35 days; fewer than eight menstrual cycles a year; failure to menstruate for four months or longer; and prolonged periods that may be scant or heavy. To regulate your menstrual cycle, you may recommend combination birth control pills — pills that contain both estrogen and progestin. These birth control pills decrease androgen production and give your body a break from the effects of continuous estrogen, lowering your risk of endometrial cancer and correcting abnormal bleeding.