New research reveals that women take greater care over their appearance when they are at peak levels of monthly fertility. The research, published in the forthcoming issue of a British journal, suggests that a genetic drive prompts women with high fertility to feel attracted to men other than their primary partners.

Researchers at the University of California worked with a group of 30 women aged 18 to 37. Full-body photographs of each volunteer were taken during various phases of their ovulation cycle. One picture was taken when the woman was close to ovulation and highly fertile, and the other at a point of low fertility in the menstrual cycle.

According to AFP reports, the observers were then asked to inspect the photos and guess which of the two showed the woman trying to look more attractive. The results indicated that the woman in her "high fertility" photograph looked nearly 60 per cent more attractive than their other counterparts.

"Though not in the same class as the obvious physical cues other primate females give when they are ovulating, it is the first evidence that women openly advertise their fertility," the British journal says. The complete paper appears in a specialist U.S. journal, hormones and behavior, published by the Society for Behavioral Neuroendocrinology.