Which method of contraception involves the use of a barrier to prevent sperm from entering the uterus?

The method of contraception that involves the use of a barrier to prevent sperm from entering the uterus is a condom. Condoms are designed to fit over the penis or line the vagina and serve as a physical barrier that blocks sperm from reaching the egg, thereby preventing fertilization. They are one of the most commonly used forms of barrier contraception and also provide additional benefits such as protection against sexually transmitted infections (STIs).

In contrast, other methods listed do not act as barriers. An intrauterine device (IUD) is a small device inserted into the uterus that alters the environment to prevent fertilization. The birth control pill works hormonally to prevent ovulation, and while the sponge does contain spermicide, it functions as a more generalized barrier method rather than specifically blocking sperm entry like a condom does.