text: Fingerprints may provide important clues about life in the womb, and may even become useful as predictors of disease risk. US researchers, in Atlanta and New York, have now shown that differences in fingerprints between the thumb and little finger are associated with likelihood of developing diabetes later in life.
  A person’s fingerprints are set for life by around the 19th week of gestation, roughly halfway through a normal pregnancy. Most organs, including the pancreas, are also formed by that time. Henry Kahn at the Centers for Disease Control and Prevention in Atlanta and colleagues decided to look at quantitative differences in ridges between the first and last fingertips – the thumb and pinkie.
  The team speculated that any disturbances during their formation might also say something about the state of the pancreas, and possibly the likelihood of a person developing diabetes as they age. Diabetes results from the failure of the pancreas to produce insulin, or enough insulin, which the body needs to help it take up glucose.
  The researchers studied 569 Dutch people, some of whom were in the womb during the Dutch famine of 1944 and 1945, dubbed the “hunger winter”. Kahn and his team tested the volunteers’ glucose tolerance – a measure which is abnormally high in people with diabetes – and also counted the number of ridges on their thumbs and little fingers by rolling the inked digits onto paper.
  Fingerprint ridges are counted in a specific way – prints with a large whorl often have a higher ridge count. The researchers found that people with normal glucose tolerance had an average difference of 6.4 ridges between the two digits, whereas people with diabetes had a much higher “ridge count gradient”, at about 8.3.
  “The field needs a way to assess how the human fetus was doing before the end of pregnancy,” says Kahn, who reported the findings at a meeting on Developmental Origins of Health and Disease in Toronto, Canada in October. “This is a tool that could give us a glimpse at the early fetus. It’s accessible and it’s cheap.”
  He believes the some of the signalling factors which influence organ growth may also affect formation of the fingertips, giving an insight into conditions in the womb.
  The team also analysed the data according to the month of conception and found that there was a seasonal effect: normal and diabetic participants conceived in late winter had lower ridge count differences between them compared with those conceived in late summer.
  But the seasonal pattern was wiped out in people exposed to the famine, they found . This suggests that environmental factors must play a role. “Was it the food? Maternal stress hormones?” Kahn asks.
  “I think there’s probably something in this,” says John Manning, a psychologist at the University of Central Lancashire in Preston, UK, who studies finger-length ratios. “There’s a lot of information in the fingers, in terms of what happens prenatally. We don’t know what kinds of conditions control them.” He agrees with Kahn that signalling factors, such as a group of proteins known as “sonic hedgehog”, may be involved, but he also suspects a role for hormones.