Research has found that women at their monthly peak of fertility unconsciously engage in certain self-embellishing behaviors, such as shopping and more provocative dressing [source: University of Minnesota]. Evolutionary biologists attribute these ovulation-specific patterns to humans' innate imperative to reproduce. By that logic, when the female body is most primed to become impregnated, it sends out readiness signals to surrounding men and also heightens the woman's awareness of potential suitors.
For instance, psychologists at the University of Trom in Norway tracked women's pupil dilation, a physiological response to attraction, at multiple intervals during their menstrual cycles. Viewing a series of sexually stimulating photographs each time, participants' pupil dilation was most pronounced during the women's ovulatory phase -- unless they were taking oral birth control [source: Laeng and Falkenberg]. Women on the pill demonstrated no such additional stimulation, even in response to a photo of their current sexual partner. Granted, pupil dilation or lack thereof likely doesn't make or break a someone's love life, but it's nevertheless a benign indicator of how hormonal contraception possibly trifles with sexual response.