The World Health Organization listed combined (estrogen plus progestin) oral contraceptives and combined hormone replacement therapy as "Group 1 carcinogens" in July 2005. [7,8] These findings provide additional biological support for an independent link between abortion and breast cancer because the biological basis for all three breast cancer risks is the same. | The World Health Organization listed combined (estrogen plus progestin) oral contraceptives and combined hormone replacement therapy as "Group 1 carcinogens" in July 2005. [7,8] These findings provide additional biological support for an independent link between abortion and breast cancer because the biological basis for all three breast cancer risks is the same. |