A woman´s hips are shaped at puberty when the growth of the hip bones is controlled by sex hormones but is also influenced by the level of nutrition. Every woman has a unique sex hormone profile which is established at puberty and persists through her reproductive life. The study´s findings show for the first time that the pubertal growth spurt of girls is strongly associated with the risk of breast cancer in their daughters.

The authors of the study followed up on 6,370 women born in Helsinki from 1934 to 1944 whose mothers´ pelvic bones were measured during routine prenatal care. The study found that breast cancer rates were more than three times higher among the women in the cohort, born at or after term, whose mothers had wide hips. They were more than seven times higher if those mothers had already given birth to one or more children.

A woman´s vulnerability to breast cancer, the study found, was greater if her mother´s intercristal diameter - the widest distance between the wing-like structures at the top of the hip bone - was more than 30 centimetres. The risk also was higher if these wing-like structures were round. The breast cancer risk was 2.5 times higher for the daughters of women in whom the widest distance was more thanthree centimetres greater than the distance at the front.

The authors of the study could only speculate, they said, on the exact nature of this adverse effect but pointed out: “Catechol estrogen, a metabolite or estradiol, is thought to cause chromosomal instability by breaking DNA strands. High catechol estrogen concentrations in the maternal circulation could produce genetic instability in differentiating breast epithelial cells, which would make the breast vulnerable to cancer in later life.”