Looking to get pregnant? According to a new study, having lots of sex as often as possible may up your chances of getting a visit from the Stork. A team of researchers from Indiana University recently found that sexual activity, even during non-fertile periods, triggers physiological changes in the body that can overall increase a woman’s chances of getting pregnant.

Although doctors have long advised couples looking to become pregnant to have sex as often as possible, a new study recently published in both Fertility and Sterility and Physiology and Behavior may have finally revealed why this practice can actually help increase a couple’s chances of conceiving. The study consisted of 30 healthy premenopausal women who were not taking hormonal or immunoactive medications. A total of 14 were sexually active and 16 were not. To investigate the link between sexual activity and fertility, the team took the women’s saliva samples at four time points: menstrual, follicular, ovulatory, and luteal phases.

Results revealed that sexually active women were significantly more likely to express distinctive changes in the immune system’s helper T cells and immunoglobulin during their non-fertile periods. The immune system works to fight off invading pathogens and microbes by activating antibodies. In order to get pregnancy, the female’s body needs to bypass this autoimmune response, and let down its defenses in order to allow the sperm to successfully fertilize an egg. According to the study, the shift in immunity that women experience after having sex may be a direct response to this dilemma.

"This research is the first to show that the sexual activity may cause the body to promote types of immunity that support conception," lead researcher Dr. Tierney Lorenz explained in a recent statement. "It's a new answer to an old riddle: How does sex that doesn't happen during the fertile window still improve fertility?"

According to the press release, there are several types of helper T cells and immunoglobulin in the immune system, and levels of those specifically associated with aiding in pregnancy were seen to have risen in sexually active non-pregnant women. Higher levels of type 2 helper T cells, which help the body accept foreign bodies that may aid in reproduction, such as sperm and developing embryos, were observed in the sexually active non pregnant women. Sexually active women also had higher levels of immunoglobulin G, an immune system cell typically found in the blood which helps to fight disease without interfering with the uterus.

"The sexually active women's immune systems were preparing in advance to the mere possibility of pregnancy," Lorenz said.

Along with helping us to better understand human reproduction, this finding may be especially useful in helping doctors identify the reasoning behind changes in natural blood test results found in women with certain autoimmune disorders. This is not the first new major immune system finding of the year. In June, researchers discovered a “missing link” between the immune system and the brain — a finding that could change the way we study disease. These new studies have added to growing consensus that suggests that the immune system is not just a passive system waiting to be activated by invading pathogens, but actually an interactive network that reacts to external cues.

Source: Lorenz TK, Heiman JK, Demas GE. Sexual activity modulates shifts in TH1/TH2 cytokine profile across the menstrual cycle: an observational study. Fertility and Sterility. 2015.