A monogamous relationship means that both you and your partner engage in sexual activity with no one but each other. While monogamy is not an effective method of birth control, it does minimize the risk of contracting sexually transmitted diseases. As long as both you and your partner are free of diseases and remain committed to each other, you will remain free of diseases. Abstinence and monogamy are both highly effective safe sex methods. Abstinence is effective at preventing both pregnancy and diseases while monogamy helps to prevent diseases only.