Sex at Any Time May Spur Immune System Changes That Boost Fertility

(HealthDay News) — Sex at any time in a woman’s menstrual cycle may trigger immune system changes that boost the likelihood of getting pregnant, a new study suggests. 

The findings were published recently in the journals Fertility and Sterility and Physiology and Behavior.

The findings are based on information from 30 women who participated in the Kinsey Institute’s Women, Immunity, and Sexual Health Study. Half of the women were sexually active and half were abstinent.

The researchers found clear differences in immune system regulation between women who are sexually active and those who are not. The findings could eventually prove useful for couples trying to conceive, the researchers said.

“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 ‘nonfertile’ periods — although it’s unclear how this works,” lead investigator Tierney Lorenz, PhD, from the Indiana University at Bloomington’s Kinsey Institute, said in a university 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?”


  1. Lorenz TK, Heiman JR, Demas GE. Sexual activity modulates shifts in TH1/TH2 cytokine profile across the menstrual cycle: an observational study. Fertil Steril. 2015;doi:10.1016/j.fertnstert.2015.09.001.
  2. Lorenz TK, Heiman JR, Demas GE. Interaction of menstrual cycle phase and sexual activity predicts mucosal and systemic humoral immunity in healthy women. Physiol Behav. 2015;152(Part A):92-98.