This answer may surprise you: no! Research has found that rates of STIs don’t differ when you compare people in monogamous and consensually non-monogamous relationships. Of course, monogamy in theory should prevent STIs, but monogamy is often implemented imperfectly. For example, people may enter a monogamous relationship without getting tested first, which means they could be bringing an STI into the relationship. Likewise, many monogamous people cheat, and when infidelity occurs, people often don’t use protection or tell their partner about it afterwards, which creates more opportunities for STIs to spread. By contrast, people in open relationships take more precautions: they practice safer sex more often, communicate more about their sexual activities with others, and get tested more frequently.