All that waiting around to be born can be a drag – so it’s little wonder that babies yawn in the womb.
New research using 4D scans shows that as well as hiccupping, swallowing and stretching, unborn foetuses also engage in frequent fits of yawning.
But these episodes decrease from 28 weeks, suggesting that they are part of helping the nervous system to mature.
Until now, there has been some dispute over whether babies are simply opening their mouths rather than actually yawning, but the study from Durham and Lancaster universities seems to prove – based on the duration of mouth opening – that more than half are, indeed, classic yawns.
As well as being rather endearing, the findings may also have positive health benefits for unborn children.
Researchers studied eight female and seven male foetuses from 24 to 36 weeks gestation. Yawning was found to decline after 28 weeks to nothing by 36.
The study, published today in the prestigious academic journal PLOS ONE, posits that yawning could be linked to foetal development and so could provide further medical indication of the baby’s health.
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Lead researcher Dr Nadja Reissland said: “The results of this study demonstrate that yawning can be observed in healthy foetuses and extends previous work on foetal yawning. Our longitudinal study shows that yawning declines with increasing foetal age.
“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.
“Given that the frequency of yawning in our sample of healthy foetuses declined from 28 weeks to 36 weeks gestation, it seems to suggest that yawning and simple mouth opening have this maturational function early in gestation.”
She said yawning could be related to the maturing of the central nervous system but that further research was needed: "It may be that, in order to get part of the brain to mature in the correct way, you need a certain stimulus, and yawning might be that stimulus.”
Last year the same group of scientists published work that showed expressions that looked like babies crying and laughing in the womb.