blood clots and certain other rare adverse effects.

Ethinylestradiol was developed in the 1930s and was introduced for medical use in 1943. The medication started being used in birth control pills in the 1960s. Ethinylestradiol is found in almost all combined forms of birth control pills and is nearly the exclusive estrogen used for this purpose, making it one of the most widely used estrogens. In 2023, the combination with norethisterone was