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Foetus yawning may be developmental marker

New research finds a foetus does yawn but not because it's sleepy
WebMD UK Health News
Medically Reviewed by Dr Farah Ahmed

22nd November 2012 - Ultrasound scans of the faces of babies in the womb have shown they don't just open their mouths - they yawn. The study, by Dr Nadja Reissland from the University of Durham and colleagues at other institutions, suggests that trends in yawning behaviour may potentially be used to track healthy foetal development.


Image: Dr Nadja Reissland/PLoS ONE

A real yawn

The research published in the journal PLOS ONE used 4D scans. Dr Reissland told us via email: "Other researchers have "discovered" yawning in the womb. However, there are very few studies and we added to the literature: first we used 4D scans and hence were able to analyse frame by frame movement of the lips and jaw; we coded from the time the lips started to part to the time they closed and could show that the difference between opening the mouth widely and yawning lies in the dynamics of the movement with yawning having a longer opening part of the movement cycle compared with the closing part."

She says in contrast wide mouth opening with jaw drop has an equal opening and closing duration.

The researchers found that between 24 to 36 weeks of gestation they were consequently able to distinguish between yawns and simple mouth openings on ultrasound images of foetal faces.

They carried out 58 scans and observed 56 yawns and 27 non-yawn mouth openings.

More research needed

Yawning is poorly understood but is often said to be infectious so that thinking or reading about yawning results in a yawn. The study reports that children are immune from the contagious nature of yawning until around five years of age which suggests the social context of yawning has a developmental component which is as yet unexplained.

The 15 healthy foetuses in the study (eight girls and seven boys) were observed four times and showed a strong decline in the frequency of both yawns and non-yawn mouth openings as gestational age increased.

The foetuses being studied obviously didn't yawn because it was contagious, neither, says Dr Reissland did they yawn because they were sleepy. Instead she believes frequency of yawning in the womb might be related to brain development.

"Lots more research needs to go into this. I have written another article on foetal facial complex movements and my idea is to use behavioural fine grained analyses to detect differences between healthy and compromised foetuses. However, at the moment I have only examined healthy foetuses to establish a baseline. The next part (for which we need funding) is to look at unhealthy foetuses."

Reviewed on November 22, 2012

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