Factors like smoking, drinking or overweight during pregnancy play a key role in determining the risk of the child developing cancer, says a new study.
Professor Ricardo Uauy, an adviser to the United Nations and the World Health Organisation, said that although cancer risk is usually associated with people's genes and their behaviour as adults, women's lifestyles before getting pregnant and while carrying their baby have a major impact on whether their child will develop the disease.
"Someone's risk of developing cancer starts from before the time of conception. The risk factors are already operating in the mother's eggs before conception," The Guardian quoted Uauy as saying.
Uauy advised that women should stop smoking before they start trying to conceive, because that increases the chances of the child having a low birth-weight. They should not drink alcohol, take an iron tablet if necessary, and ensure they get at least 400mg of folate every day.
Children born lighter than average often then put on weight quickly, but in the form of fat rather than muscle, and develop fat around the middle, which raises cancer risk.
"Mothers-to-be only need to consume an extra 150 calories a day during the nine months of pregnancy, and should not 'eat for two'," stressed Uauy.
Babies should not eat any solid food until they are six months old, nor be given any sweet drinks such as fruit juices in case that encourages an appetite during childhood for sugar-laden drinks, which promote weight gain.