Which device can allow sexually transmitted diseases to move from the vagina into the uterus and may lead to pelvic inflammatory disease?

The correct answer is an intrauterine device (IUD). This device can facilitate the movement of bacteria and other pathogens from the vaginal environment into the uterus. The presence of an IUD can create a pathway for these microorganisms, which may lead to pelvic inflammatory disease (PID) if pathogens ascend from the vagina into the upper reproductive tract. PID is a serious condition that can result in long-term health issues or infertility.

Other options are not associated with the same risk. Condoms act as a barrier to prevent the exchange of bodily fluids during sexual activity and are effective in reducing the risk of transmitting sexually transmitted infections. Diaphragms also serve as a physical barrier, whereas birth control pills primarily work by altering hormonal levels to prevent ovulation; they do not create a direct pathway for pathogens into the uterus. Thus, while other contraceptive methods have their specific functions, an IUD uniquely poses a risk for allowing the introduction of pathogens to the upper reproductive tract, making it a potential contributor to pelvic inflammatory disease.