E-Mail IMAGE: Fluorescence stereo micrograph of a mouse mammary gland intraductally injected with normal human breast epithelial cells. Credit: Marie Shamseddin (EPFL). view more Credit: EPFL Hormonal contraceptives, e.g. the pill, the patch, and the vaginal ring, contain synthetic hormones that prevent pregnancy by either stopping ovulation, changing the cervical mucus to stop sperm from passing through the cervix and finding an egg, or changing the womb's lining to prevent a fertilized egg from being implanted in it. Despite their widespread use, hormonal contraceptives are known to increase the risk of breast cancer, which is the most common cause of cancer-related death among women worldwide, and also topped the list of most commonly diagnosed cancers in 2020.