Being a twin may reduce the risk of developing childhood cancer, research suggests.

A study has found that twins are 20% less likely to develop childhood cancer than the rest of the population.

At this stage the results are preliminary, and Cancer Research UK scientists are to carry out a larger scale international study to try to confirm the findings.

The researchers looked at 13,000 twins born in or around Oxfordshire between 1963 and 1989.

They found just 15 cases of childhood cancer - four fewer than would be expected in an average population of this size.

The team will now analyse other data sets, including a much larger one of children born within the Mormon community in Utah to see if they can confirm their findings and measure the risk reduction more precisely.

They will study 50,000 babies born as twins, together with non-twin siblings, and 50,000 non-twins as a comparison group.

Surprising results

Lead researcher Dr Mike Murphy, of the Cancer Research UK general practice research group in Oxford, said: "Because children's cancer and twinning are both comparatively rare, really large studies are needed to investigate the relationship."

He said the team were "surprised and intrigued" by the results and it would be exciting to take the work to a much larger sample.

"Of course the really interesting question is why twins should be at reduced risk," he said.

"Answering that could give us some important information about the factors that contribute to childhood cancer, which in turn could help us with prevention or treatment."

Twin pregnancies have different foetal and placental mass and associated hormone levels compared to standard pregnancies.

It could also be that, as twins are typically smaller than single new-borns, they have a greater tendency to die of something else so the cancer does not get a chance to appear.