Not that you really need it, but here’s another reason to have sex: It’s great for your immune system. According to new research, frequent coitus triggers the body’s natural defenses in positive ways and may jumpstart physiological changes that boost a woman’s chance for conceiving.

The results of the study were published Tuesday in two papers, one in the journal Fertility and Sterility and another in the journal Physiology and Behavior. The papers suggest that having sex during points of infertility in a woman’s cycle could still help improve her chance of conceiving.

Sex and immune systems

For years, physicians have known that sex outside of a woman’s fertile period could increase her chances for getting pregnant, but they weren’t sure why. The study sought to make sense of this biological conundrum. “It’s a new answer to an old riddle: How does sex that doesn’t happen during the fertile window still improve fertility?” Tierney Lorenz, a visiting research scientist at the Kinsey Institute and lead researcher on the study, said in a press statement.

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