The first orally active semisynthetic steroidal estrogen, EE (17α-ethynylestradiol), the 17α-ethynyl analog of E2, was synthesized in 1938 by Hans Herloff Inhoffen and Walter Hohlweg at Schering AG in Berlin.
A study in the BMJ, with over 1.6 million women, found that users of vaginal rings with ethinyl estradiol and etonogestrel have a 6.5 times increased risk of venous thrombosis compared to non-users.