Washington, July 4: High-fat diet in pregnancy may increase the risk of breast cancer over generations, a new study has revealed.Feeding pregnant female mice a diet high in fat derived from common corn oil resulted in genetic changes that substantially increased the susceptibility of breast cancer in three generations of female offspring, according to the study published online in the journal Breast Cancer Research on Monday."It is believed that environmental and life-style factors, such as diet, plays a critical role in increasing human breast cancer risk, and so we use animal models to reveal the biological mechanisms responsible for the increase in risk in women and their female progeny," senior author Leena Hilakivi-Clarke, professor of oncology at the Georgetown University, said.The new study revealed a number of genetic changes in the first and third female generations of mice that were fed high-fat diets during pregnancy, including several genes linked in women to increased breast cancer risk, increased resistance to cancer treatment, poor cancer prognosis and impaired anti-cancer immunity.In the new study, the amount of fat fed to the experimental mice matched what a human might eat daily. But both the experimental mice and the control mice ate the same amount of calories and they weighed the same.The experimental mice got 40 per cent of their energy from fat, and the control mice got a normal diet that provided 18 per cent of their energy from fat. The typical human diet now consists of 33 per cent fat, according to the study."Studies have shown that pregnant women consume more fat than non-pregnant women, and the increase takes place between the first and second trimester," Hilakivi-Clarke said."Of the 1.7 million new cases of breast cancer diagnosed in 2012, 90 per cent have no known causes," she said, adding "Putting these facts, and our finding, together really does give food for thought."