If there’s one thing we know, it’s that having sex increases your chances of getting pregnant. But, there’s actually scientific evidence that more sex increases your fertility, and not just right before or after your period. Two recent studies indicate that your immune system is the key. One study revealed that women who were more sexually active had greater changes in their T cells, an essential component in our immune systems, and the proteins that T cells communicate with. Women who were sexually active had higher levels of immunoglobulin G during the luteal phase (where the uterine lining thickens in preparation for pregnancy) and higher levels of immunoglobulin A during the follicular phase (when ovaries’ follicles are maturing). Your body may be readying itself to get pregnant, whether you’re watching the calendar or not.