A fat-laden diet during pregnancy may lead to an increased risk of breast cancer that is passed down generations, say scientists. Pregnant women who dine on junk food could unwittingly be risking the future health of not only their daughters but also their grand-daughters, research suggests.

The US study, conducted on rats, provides further evidence that environmental factors can cause inheritable genetic changes. Scientists believe the findings have an important message for humans. "The implications from this study are that pregnant mothers need to eat a well balanced diet because they may be affecting the future health of their daughters and granddaughters," said lead researcher Dr Sonia de Assis, from Georgetown University in Washington DC.

The researchers fed a group of mother rats either a high-fat or normal diet and looked at what happened to their offspring and the subsequent generation.

They found that not only did a high-fat diet increase the risk of daughters having breast cancer, but also granddaughters: the risk was not only passed on by daughters but also sons.

Daughters of male and female rats who both had fat-consuming mothers had an 80% chance of developing breast cancer.

But the risk fell to 69% if the mother of one parent - either father or mother - had a high-fat diet and the other grandmother had a normal diet during pregnancy.