Menstruation is a natural process that affects women's bodies in many ways, including their sex drive. During this time, several physiological factors can contribute to an increased sexual desire for some women. Hormones play a big role in influencing libido during menstruation. Levels of estrogen and testosterone naturally rise during the follicular phase (days 1-14) of the menstrual cycle—the two weeks leading up to ovulation—which can lead to higher levels of arousal and libido. During this same period, progesterone levels decrease which can also contribute to an increase in sex drive and sensitivity. Fluctuations in body temperature may also cause heightened sexual desire during menstruation.