Couples trying to have a baby may have a big question mark in their thought clouds. Seemingly so basic but there is that big -- how?

Findings of a new study revealed that sexual activity sets off physiological changes in the woman's body that boost her chances of getting pregnant even outside of her fertile period.

The study may possibly influence recommendations on how often couples should engage in sexual intercourse if they are trying to conceive a child.

Doctors have long recommended that couples who want to have a baby have sex as often as possible but the new study finally revealed why this could actually improve a couple's odds of conceiving.

The body's immune system fights invading microbes and other pathogens by activating antibodies. In order to get pregnant, the female body has to bypass this autoimmune response so the sperm can successfully fertilize the egg.

For the study, which involved 30 women, 14 of whom were sexually active and 16 were not, researchers found that the sexually active participants were more likely to have higher levels of type 2 helper T cells that help the body accept foreign bodies that may help in reproduction such as sperm and developing embryos.

The sexually active participants were also observed to have higher levels of immunoglobulin G, an immune system cell often found in the blood and is known to fight diseases without interfering with the uterus.

The researchers found higher levels of type 2 helper T cells and immunoglobulin G in sexually active women during the period when the uterine lining thickens to prepare for pregnancy. They also observed higher levels of type 1 helper t cells and immunoglobulin A during the period when the follicles of the ovaries are maturing.

"We're actually seeing the immune system responding to a social behavior: sexual activity," said study researcher Tierney Lorenz, from Kinsey Institute. "The sexually active women's immune systems were preparing in advance to the mere possibility of pregnancy.

These changes in the immunity though were not observed in women who were not sexually active.

"These results support the hypothesis that shifts in immune response across the menstrual cycle may reflect tradeoffs between reproduction and immunity. These findings point to the need for further research on the interaction between sexual behavior, the menstrual cycle, and immune response," the researchers wrote in their study, which was published in Fertility and Sterility on Sept. 15. 

Photo: Anthony Easton | Flickr 

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