Scientists have shown conclusively for the first time that unborn babies yawn repeatedly in the womb.
But it is not because they are sleepy or bored. The most likely explanation is that foetal yawning is an essential process linked to brain development.
While it is well known that foetuses open and close their mouths, experts have disagreed over whether or not they are actually yawning.
The new study, using high resolution ultrasound footage, confirms that they really do yawn, and do it often.
Dr Nadja Reissland, from the University of Durham, who led the study of seven male and eight female foetuses from six to nine months of pregnancy, said: "The results of this study demonstrate that yawning can be observed in healthy foetuses and extends previous work on foetal yawning.
"Unlike us, foetuses do not yawn contagiously, nor do they yawn because they are sleepy. Instead, the frequency of yawning in the womb may be linked to the maturing of the brain early in gestation."