Ethinyl estradiol is a synthetic form of the female sex hormone estrogen that is commonly used in combination with a progesterone hormone in birth control pills. These hormones prevent the release of an egg during ovulation. They also change both the cervical mucus and the uterine wall to keep sperm from fertilizing an egg. Combined, these measures vastly reduce the likelihood that you’ll get pregnant. These combination pills may also contain an iron or B vitamin supplement.










