Experts believe caffeine may damage the DNA of unborn children and make them more susceptible to the disease.
Previous research has shown that caffeine can induce changes to DNA that reduce the ability of cells to withstand cancer triggers such as radiation.
Changes of just this kind have been seen in the blood cells of children with leukemia. Scientists have determined that they occur before birth in the womb, but no one knows why.
Dr Marcus Cooke, from the University of Leicester, who is leading the research, said, "It's been known for years that caffeine is a radiosensitizer that enhances the effects of DNA-damaging agents. It does this in two ways, by interfering with the process of DNA repair and by pushing cells through the cell replication cycle so they don't have time to make repairs.
"Although there's no evidence at all of a link between caffeine and cancer, we're putting two and two together and saying: caffeine can induce these changes, and it has been shown that these changes are elevated in leukemia patients. I wonder if caffeine can somehow sensitize cells or increase the risk of leukemia?
"The idea seems plausible. People have looked at the blood of children with leukemia and seen that these DNA changes are more prevalent than they are in children without leukemia. We know they occur in utero (in the womb), but we don't know the cause."
Leukemia affects the bone marrow and white blood cells. Around 7,000 cases of the disease are diagnosed each year in the U.K., but only one in 10 leukemia patients are children. Nonetheless, it is still the most common type of childhood cancer, accounting for 35% of all cases.
There is no single proven cause of childhood leukemia. Two possible triggers are thought to be pre-birth exposure to man-made or natural radiation, or an unusual response to a common infection. However the evidence for both is inconclusive.
Cooke's team is undertaking a year-long pilot study working with a group of 1,340 pregnant women.
DNA tests will be carried out on blood samples taken from the newborn babies, and the results matched against their mothers' caffeine intake.
The scientists will look for correlations between caffeine consumption levels, and the frequency at which DNA changes of the sort that are associated with leukemia occur.
If a pattern emerges, the scientists will seek further funding to see whether babies with caffeine-linked DNA changes are more likely to develop leukemia. This longer study, lasting three years, will also examine evidence of exposure to other DNA-damaging agents and collect more lifestyle and dietary data from the mothers.
The research is supported by the World Cancer Research Fund (WCRF).
Cooke said, "Caffeine might or might not be acting on its own, and we could be looking at very subtle effects. Whether or not we will be able to spot them is hard to say. You just have to go ahead and do the study and see what the frequencies of these changes are, but we've done a statistical analysis which shows there's a good likelihood that we will see an effect."
The Food Standards Agency advises pregnant women not to consume more than 200mg of caffeine a day, equivalent to two cups of coffee. It says there is evidence that excessive caffeine consumption during pregnancy can affect fetal growth and lead to low birth weight.
From the February 2, 2009, Prepared Foods E-dition