While yawning maybe a sign of tiredness or boredom in adults, in foetus’ it might be a trigger for brain development! Making this complex muscle movement could send nerve impulses to the brain, helping it function normally. Others however feel that all this hogwash and the babies are simply opening their mouth. But now Durham University researchers claim to have resolved the debate after scanning 15 healthy foetuses four times between 24 and 36 weeks’ gestation.
By timing how long the mouth spent opening to its widest point, compared with how long it spent closing, they were able to distinguish between a yawn and a simple mouth opening. This is surprising because while yawning is contagious among adults, the tendency to follow someone else’s yawn doesn’t show in children at least till they are five.
Previous studies have suggested that there is a ‘U-shaped’ developmental progression in yawning, because premature babies yawn more than those born on term, but primary schoolchildren yawn more than kindergarteners. The new paper supports this theory, demonstrating that yawning episodes among foetuses decreased from an average of two an hour at 24 weeks’ gestation to none by 36 weeks.
Dr Nadja Reissland, who led the study, said the results ‘seem to suggest that yawning and simple mouth opening have this maturational function early in gestation’. ‘The yawn itself might target certain parts of the brain to develop. As an adult you might yawn because your brain is telling you are tired, but here it is the other way around, the yawn is triggering the brain maturation,’ she explained.
‘[Next] I would like to look at compromised foetuses, for example foetuses that have been exposed to drugs in the womb or which have some sort of genetic defects, and see if they yawn in a different way or at a different time. Then you could use it as an indicator for doctors to have a look at – it could be a measure of healthy development.’