Recent research has revealed that many aspects of female sexuality change across the menstrual cycle. Samantha J. Dawson, Kelly D. Suchinsky, and Martin L. Lalumiere from the Department of Psychology at the University of Lethbridge decided to examine this by looking at changes in sexual fantasies across the menstrual cycle.
Here’s one of the key findings of the study: The number of males in the fantasies increased during the most fertile period, with no such change for the number of females. Or in other words…
Women fantasized more about multiple male partners when they were most fertile, whereas at other times of the month almost all fantasies featured a single man.
The abstract of the study can be found here: https://link.springer.com/article/10.1007%2Fs10508-012-9939-1