Everybody has heard of the fertile days in the woman's cycle . Having intercourse during this period, greatly increases chances of conception because it is closest to the day of ovulation or egg release. It is now evident that increasing the frequency of sexual intercourse through out the cycle can boost up chances of getting pregnant. Research shows that couples who had intercourse very frequently through out the cycle had a much higher chance to get pregnant compared to those who tried getting pregnant only during the mid cycle ovulation time. Several reasons have been postulated. Frequent intercourse may have favorable effects on the woman's immune system, and this may promote egg-sperm interaction as well as preparation of the womb for conception. In men, frequent ejaculation may improve sperm integrity and capacity to impregnate the egg. 

Although there is no clear recommendation on exactly how often a couple need to have intercourse in a month to improve conception, it's clearly beneficial to try as regularly as is comfortable for each couple.