New pictures show, for the first time, that babies yawn in the womb.
Durham University researchers were curious if foetuses yawned and, if so, why. They gave 15 pregnant women 4D ultrasound scans four times during their pregnancy. The last was done at 36 weeks, just a few weeks before the eight girls and seven boys were born.
Rather then the grainy, flat images produced by the 2D scanners usually used, a 4D machine stitches together pictures taken from a variety of angles to create clear three-dimensional images.
These are then recorded on video - the fourth dimension. Researchers painstakingly analysed these highly detailed videos frame by frame to see how the foetuses moved their mouths.
Some academics believe that rather than yawning, the babies are simply opening and closing their mouths.
But researcher Nadja Reissland said the scans provided clear evidence that they yawn.
On some occasions, a baby would slowly open their mouth, before quickly snapping it shut - characteristics of a yawn.
The analysis revealed that the youngest babies yawned the most, but there was no difference between the sexes.
Dr Reissland calculated that if she had been able to monitor the babies for longer, she would have caught them yawning an average of six times an hour.
She was not sure why they yawned, but said it was unlikely to be because they were tired. Instead, she believes that the long, slow stretch could help the development of brain regions involved in the movement of the jaw.
If yawning is a sign of brain development, Dr Reissland believes it could one day be added to the indicators doctors use to determine whether a foetus is developing normally.
Her findings were published in the journal PLoS ONE.
- DAILY MAIL