Babies Yawn in the Womb

Yawning in unborn babies appears to be normal development stage

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) Spending nine months in the same small space sure could get boring. So perhaps it's not surprising that scientists have discovered babies yawn in the womb. Of course, the babies are not yawning because they are bored or tired.

The researchers are not entirely sure why any creature yawns.

The yawns in unborn babies appear to be just a normal stage of development while the baby is growing inside mom.

"Attend all prenatal visits."

The study that determined babies yawn was led by Nadja Reissland, DPhil, from the Department of Psychology in the University of Durham in the United Kingdom. The researchers scanned 15 healthy babies while still in the mother's womb using 4D ultrasound technology. The ultrasounds were done at 24, 28, 32 and 36 weeks of pregnancy.

The researchers watched how the babies opened their mouths on the scans at each stage of development. They wanted to compare simple mouth openings with true yawns. The researchers measured how long it took for the babies' mouths to reach the point where they were open the widest.

If the babies spent more than 50 percent of the the time their mouths were open to open it to the widest point, the researchers classified that as a yawn. They also looked at whether the number of times the babies yawned changed over time. They found that the babies yawned less and less after the 28th week of pregnancy.

Among the babies scanned, eight were girls, and seven were boys, but there was no difference between the genders related to yawning.

"Unlike us, fetuses do not yawn contagiously, nor do they yawn because they are sleepy," said Dr. Reissland in a release about the study. "Instead, the frequency of yawning in the womb may be linked to the maturing of the brain early in gestation."

The study was published November 22 in the journal PLOS ONE. The research was funded by the Economic and Social Research Council.

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Review Date: 
November 22, 2012
Last Updated:
November 26, 2012