Waist-hip ratio (WHR) is a tool to assess the distribution of body fat. The ideal number is 0.7, which means that the circumference of a woman's waist is 70% the circumference of her hips.
A ratio under 0.6 may signal hips that are not well suited to childbirth, and a ratio in excess of 0.8 could suggest fertility difficulties related to being overweight.
The smaller the waist in relation to the hip, the more desirable a woman is seen to be.