Larger babies have higher risk of developing certain cancers in adulthood, research suggests.
Hormones may be the key
UK and Swedish researchers found higher rates of digestive and lymphatic cancer among people who were big at birth.
Bigger female babies went on to have significantly higher rates of breast cancer - but much lower rates of cancer of the womb lining.
Details are published by the online edition of the International Journal of Cancer.
The researchers, from the London School of Hygiene and Tropical Medicine and the Universities of Uppsala and Stockholm examined the records of 11,166 babies born between 1915 and 1929 in Sweden.
Of these one in four was diagnosed with cancer between 1960 and 2001.
The researchers found that each increase in birth weight of 450g was associated with a 17% increase in lympathic cancers, and a 13% increase in digestive cancers, including stomach, colorectal and pancreatic cancer.
Women in the highest category of birth weight (4kg or greater) were four times as likely to get breast cancer before age 50, than those who weighed less than 3kg.
In contrast, women who were large at birth were only half as likely to get endometrial cancer as their smallest counterparts.
The researchers accept that some of their findings may have arisen by chance.
They also stress that birth weight only seems to be associated with an increased risk of certain cancers - and by no means all forms of the disease.
However, they speculate that the conditions inside the womb - for instance the levels of circulating hormones - may have a direct impact on the later chances of developing cancer.
Researcher Miss Valerie McCormack told the BBC News website: "In utero levels of some hormones may affect cancer risk just as adult levels of growth hormones are correlated with risk.
Previous studies have found associations between smaller birth size and increased risks of adult heart disease and diabetes.
Professor John Toy, medical director of Cancer Research UK, said: "This study's findings are intriguing and, if totally correct, suggest that the susceptibility of developing certain types of cancers could be linked to the very early development of the cells of the body and its organs.
"The statistical analysis of the results are less robust than is usual and therefore there is room for doubt about the overall accuracy of the paper's findings."