...recent studies have found large changes in cues and behavior when a woman is at this stage of peak fertility. Lap dancers get much higher tips (unless they’re taking birth-control pills that suppress ovulation, in which case their tips remain lower). The pitch of a woman’s voice rises. Men rate her body odor as more attractive and respond with higher levels of testosterone.I would recommend reading the whole article, which describes experiments supporting rather elaborate evolutionary psychology theories about maintaining breeding relationships while also enhancing genetic diversity, such as:
...the “good genes” evolutionary explanation for adultery: a quick fling with a good-looking guy can produce a child with better genes, who will therefore have a better chance of passing along the mother’s genes. But this sort of infidelity is risky if the woman’s unsexy long-term partner finds out and leaves her alone to raise the child. So it makes sense for her to limit her risks by being unfaithful only at those times she’s fertile....By that same evolutionary logic, it makes sense for her partner to be most worried when she’s fertile.