Hormonal Birth Control and Invasive Breast Cancer Risk
Contemporary hormonal contraception was found to increase the risk of invasive breast cancer in women, with the duration of use correlating to the increased risk. A study led by Lina S. Mørch, PhD, of the University of Copenhagen, looked at 1.8 million women in Denmark and found that any use of contemporary hormonal birth control—whether past or present—increases the risk of invasive breast cancer compared with no use, although the absolute increases in risk were considered to be small. The results were published in The New England Journal of Medicine.
The nationwide study included all women between the ages of 15 and 49, who had not had cancer, venous thromboembolism, or received infertility treatment. The study assessed the connection between the use of hormonal birth control and the risk of invasive breast cancer utilizing nationwide registries to provide updated information.
Duration of contraception use was a key factor in the determination of risk, with the relative risk of breast cancer increasing from 1.09 in women who used hormonal birth control for less than 1 year, up to 1.38 with use longer than 10 years. It was found that women who used contemporary hormonal contraception for more than 5 years were at an increased risk for a following 5 years, even after discontinuing use of the birth control. However, the increased risk rapidly disappeared after stopping the use of hormonal birth control after less than 5 years.