child development

Just As Bored And Sleepy As We Are: Ultrasounds Show Babies Yawning In The Womb

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I always assumed yawning was something that people did after they were born, when they were exposed to reading two-year-old copies of Family Circle magazine while waiting for a dental appointment or viewing someone else’s vacation videos. But no! Researchers say ultrasounds show babies yawning before they are even born. They are just as bored and sleepy as we are! If researchers were to study me today, they would discover I find this new so interesting because I’m exhausted from the Thanksgiving festivities of yesterday, and also my young daughter is up bright and early demanding we decorate the Christmas tree. Yawning unborn babies, I am so with you.


Researchers from Durham and Lancaster Universities recently discovered that ultrasound images show when a fetus is yawning and when it is just opening its mouth, possibly signaling a developmental marker in the womb that could provide more information on the health status of the fetus.

The study on yawing as a developmental process was recently published in the international academic journal, PLoS ONE. While past studies by scientists have argued that fetuses yawn, other studies have proposed that unborn babies are only opening their mouths slightly, and not showing a true yawn. The scientists believe that the varied findings were the result of “a lack of precise definition of yawns” that differentiated them from mouth openings.

In the current study, the scientists completed 4D scans of 15 healthy unborn babies and the images show a clear difference between “yawning” and “non-yawn mouth opening.”

“The results of this study demonstrate that yawning can be observed in healthy fetuses and extends previous work on fetal yawning. Our longitudinal study shows that yawning declines with increasing fetal age,” explained the study’s lead research Dr. Nadja Reissland of the Department of Psychology at Durham University in a prepared statement.

Based on the findings, the team of investigators believed that over half of the mouth openings found in the study could be considered “yawns.” Yawn studies were conducted with eight female and seven male fetuses during 24 to 36 weeks of gestation. While there was no major difference between yawning in males and females, yawning overall reduced following 28 weeks of gestation.

I think, and only because I’m a scientist, that the yawning decreases with advanced gestational age because the babies are able to realize that sometimes in life they will be bored and that’s okay. Maybe they just find other things to amuse themselves while in the womb like hiccuping. Or maybe there is a more science-y answer:

“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,” continued Reissland in the statement. “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.”

So yawning may be linked to brain maturity, which means that today my brain is maturing at an alarming rate because I just can’t stop yawning. I think I will use this new study on my not-baby-babies in convincing them we need a family-time nap.

(photo: Shane Trotter /shutterstock)