Women who are trying to conceive will know that with TTC comes the fertile window—the magic moment when you should have sex to get pregnant. But is timing a problem?
When you're trying to get pregnant, you focus on having sex around the time you're ovulating—in fact, there's a whole industry of ovulation tests and kits to help you determine the magical time of the month when sperm can meet egg. But new research shows that actually, having sex throughout your cycle—even when you're not fertile—can change your body's immune response, making it more receptive to an eventual pregnancy.
Sex sends a message
Two Indiana University studies published in the journals Fertility and Sterility and Physiology and Behavior looked at 30 women, about half of whom were sexually active. The researchers discovered that the women who were having sex had altered T-cells and antibodies that would make a pregnancy more accepted by the immune system, which normally wards off foreign threats to the body. "Having sex seems to be a signal to the woman's immune system to focus on the kinds of immune response that promote conception," lead author Tierney Lorenz, Ph.D., a research scientist at IU's Kinsey Institute, tells Fit Pregnancy. "Essentially, it changes the immune system's priority from defending against disease and repairing tissues, to helping along conception and implantation, and preparing for a possible pregnancy."
So how does this change happen? T-cells and antibodies help the body decide what outside invaders it should accept (for example, a pregnancy) and what it should attack. "Both antibodies and T-cells work by directing other parts of the immune system in what to do," Lorenz says. "That's why they are so important for changing how the immune system as a whole responds to different environmental cues—for example, sexual activity."
Changes in body chemistry
Previous research has shown that the immune system changes throughout the menstrual cycle, allowing pregnancy to happen after ovulation, and that sexually active women have different immune patterns than women who aren't having sex. "But no one has put those two ideas together—that sexual activity may be the necessary cue to engage these shifts, and that sexually abstinent women would have no reason to lower their defenses at any point of the cycle for a pregnancy that won't occur," Lorenz says.
Basically, having sex even when you're not ovulating prompts the body to get ready for a pregnancy. "If you were sexually abstinent and then had sex just one time during the fertile window, your fertilized egg would encounter an immune system that wasn't ready and might get in the way of the fertilized egg surviving and implanting," Lorenz says. "But, if you had primed the immune system with the frequent information that reproduction was possible—by having sex regularly—it would already be engaging in pro-pregnancy responses."
It's not clear exactly how sex tells the body this, but Lorenz has some theories. "Sex might trigger changes in hormone patterns across the menstrual cycle, or change rates of ovulation," she says. "Getting exposed to your intimate partner's microbiome, the combination of bacteria, yeasts, and other very tiny organisms that live inside and on all of us, might challenge the immune system differently than if it were not exposed to that microbiome. There might be something in ejaculate that stimulates or suppresses immunity in the female reproductive tract, or sends a signal to the rest of the immune system to change in some important way. Or there may be some other factor that is different between women who are and are not having sex, such as diet, sleep, or simply social interactions. There is a lot of research that needs to be done to figure out how sexual activity influences women's immune function."
It's also hard to say whether these findings could help women who have autoimmune disorders, which make it even more difficult for their bodies to accept a pregnancy, because the studies were only done on women with normal immune function. Although it seems promising, Lorenz says much more research in that area is needed as well.
How often to get it on
In terms of how much sex you need to have in order to receive immune benefits, "there was no magic number," Lorenz says. "In some instances just being sexually active at all in the month prior had an effect on some parts of the immune system." Because baby-making sex can sometimes feel like a chore, don't let this new info put even more pressure on you and your partner. "Ultimately, my advice is to do what works right in your relationship," Lorenz says. "But, our findings do suggest that the more frequently a woman engages in sexual activity, the more often her immune system gets the message that it's time to reproduce. Even when an individual act of sex happens outside of the 'fertile window,' it is still useful for sending that message to the immune system, and thus could potentially increase your chances of getting pregnant eventually."