Sex outside of ‘optimal' ovulation window changes immune system, increases fertility

Previous research suggests having sex boosts immunity and that doing so during the optimal ovulation window improves a couple’s likelihood of conceiving. But a new study sheds light on the relationship between those findings— and alters the second, suggesting an increased chance of fertility regardless of when a woman has sex.

Researchers at Indiana University found that sexual intercourse, even when performed outside the window of ovulation, causes physiological changes in a woman’s body that make her more fertile. 

"It's a common recommendation that partners trying to have a baby should engage in regular intercourse to increase the woman's chances of getting pregnant— even during so-called 'non-fertile' periods— although it's unclear how this works," study author Tierney Lorenz, a visiting research scientist at the Kinsey Institute at Indiana University, said in a news release. "This research is the first to show that the sexual activity may cause the body to promote types of immunity that support conception.

"It's a new answer to an old riddle: How does sex that doesn't happen during the fertile window still improve fertility?"