Hm, very good question and I can see why you question that. https://www.webmd.com/drugs/2/drug-5186/estradiol-oral/details. Femoston is the brand name of estradiol. And I don't see it used in that way. For heavy periods, it's not uncommon for girls to be put on birth control. But this one? Weird choice it appears. Some birth control pills use estrogen to decrease period issues and prevent pregnancy. But Femoston seems to be used more for peri menopausal and post menopausal women. If it were me I'd either speak to the doctor who prescribed it for further clarification or a pharmacist where you go. I agree, odd choice.