Common Relationship Structures

• Asexual or non-sexual: Asexual people do not generally have sexual feelings, and/or they choose not to have sex. People who identify as asexual may want emotional relationships, including long-term committed, loving, non-sexual partnerships. Others do have sexual feelings but do not want or do not feel ready for sexual activity with another person, so they are completely or selectively abstinent.
• Lifetime mutual monogamy: In these relationships, each person has only one sexual partner in a lifetime. Both partners only have sex with each other.
• Mutual serial monogamy: This is a common relationship structure among many adults. When someone is serially monogamous, they may have sexual contact with more than one person over a lifetime, but they only maintain one long-term sexual partnership at a time, in which both partners are monogamous (have sex only with each other).
• Mutual fidelity: Mutual fidelity is similar to mutual monogamy except that there may be more than two people involved in this kind of relationship. Groups or families of three, four or more may have sexual relationships with one another but not have sex with anyone outside the group.
• Sexually non-monogamous relationships: Sexually non-monogamous relationships include consensual/honest non-monogamy such as “casual dating,” swinging, polyamory, and open relationships, as well as non-consensual/dishonest non-monogamy, also known as cheating. There are a wide variety of sexually non-monogamous relationship structures that people may choose, in which one or more members of a couple or group have sex with others.

Though at first glance it may seem like a sexually non-monogamous person is at a higher risk of STI infection than a serially monogamous one, remember that relationship structure is only one risk factor for STIs. Other things that increase the chance of getting an STI are a high number of lifetime sexual partners, irregular STI testing and treatment, sharing needles for IV drug use, having sex with strangers or sex workers, and incorrect and/or irregular use of sexual barriers. A sexually non-monogamous person who correctly and regularly uses sexual barriers such as condoms may be less likely to get an STI than a mutually serially monogamous person who does not use barriers or has a partner of unknown STI status.