(Abstracted from N Engl J Med 2017;377:2228–2239)
It is estimated that worldwide 13% of women between the ages of 15 and 49 years use hormonal contraception. In Denmark, this percentage was 24% in 1995 and increased to 39% by 2012. Use of estrogen promotes the development of breast cancer; the role of progestin is unclear. A large number of studies have reported inconsistent findings of breast cancer risk among women who receive hormonal contraceptives. Whether contemporary hormonal contraception is associated with an increased risk of breast cancer is unknown.