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4D Scan Shows Fetus Yawning, A Sign That Could Help Identify Healthy Babies

Using 4D ultrasound scans that distinguish between yawning and simple mouth opening, researchers in the UK show that contrary to some views, fetuses do yawn, and suggest observing this behavior could be a useful way to monitor their developmental health.

Lead researcher Nadja Reissland, from the Department of Psychology at Durham University, and colleagues, write about their findings in the 21 November issue of the open access online journal PLoS ONE.

4D ultrasound scans are to 3D scans as video footage is to still photos: they are in 3D but also have a time dimension, allowing doctors and researchers to measure how long the behavior they are observing lasts for.

In their background information, the researchers explain how some researchers claim fetuses yawn while others argue it is simple mouth opening. They also note there is no developmental explanation of the difference.

So they set out to investigate, using repeated measurements, how fetal yawning develops compared with simple mouth opening.

This 4d scan shows a baby yawning in the womb - something that scientists think could be used to monitor their developing health. Photo from Reuters video below. For their study, they recorded 4D ultrasound video footage of the face and upper torso of 15 healthy fetuses (8 female and 7 male) at 24, 28, 32 and 36 weeks gestation.

They distinguish yawning from non-yawn mouth openings "by the opening part of the movement cycle being longer compared to the closing part of the cycle". (Such an observation is not possible with 3D stills, as the gape at the apex of a yawn looks the same as the gape at the apex of a simple mouth opening, say the researchers: you need the time dimension to be sure of the difference).

The results showed that over half the mouth openings were yawns, that yawning frequency declined from 28 weeks gestation, and there was no difference between males and females.

Although nobody knows what purpose yawning serves or how important it is, the researchers suggest there may be a link to fetal development, and it could serve as an index of health in unborn babies.

Reissland says in a press statement that the findings build on previous work on fetal yawning, and show the behavior lessens as fetuses grow.

"Unlike us, fetuses 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," she says, proposing that:

"Given that the frequency of yawning in our sample of healthy fetuses 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."

There is also a suggestion that yawning could be linked to development of the central nervous system, but only further studies on mothers and fetuses could confirm this.

The study was funded by the Economic and Social Research Council (ESRC).

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