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 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 heritable genetic changes.

Scientists say the findings could have important implications 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.

The researchers found that not only did a high-fat diet increase the risk of direct offspring having breast cancer, but also the next generation.

The risk was not only passed on by daughters, but also sons.

Female offspring of male and female rats which had fat-consuming mothers had an 80% chance of developing breast cancer.

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

Granddaughters of grandmother rats given a normal diet had a 50% chance of breast cancer.

Genetic changes caused by the environment that can be passed on to future generations of offspring are thought a possible cause of the increased cancer risk.