Hormone-based methods cause changes in a woman’s body that inhibit ovulation and implantation. Another group of contraceptive devices c works in a different way—by preventing sperm from reaching an ovum. In this section, we look at condoms and four cervical barrier devices. In

CD

addition, we include vaginal spermicides in this section because their effect is also to prevent sperm from reaching an egg. Other than the con­dom, barrier methods do not protect against STIs, including AIDS and genital warts (Winer et al., 2006).