Researchers at the University of Durham and the University of Lancaster conducted a study that was later published on November 21 on PLOS ONE. In the study, they concluded that even fetuses yawn. It is hoped that this study information can one day be used to understand more on the purpose of yawning in the fetus and how the yawning behavior changes through the different growth stages.
In their study, researchers studied 15 pregnant women who were pregnant for the first time. Over a period of weeks, beginning at the 24-week mark, they began to take 3D videos of the 7 female fetuses and 8 male fetuses. Videos were recorded once a month, up until the 36-week mark.
The study found that on average, the 24-week fetuses yawned around 6 times per hour. Over the weeks, the amount of yawning slowed down and eventually stopped completely at 36 weeks. To record the amount of yawns, researchers monitored the faces of the fetuses. They were able to distinguish between facial opening to prepare for breast feeding and yawning by using different study criteria.
A yawn was defined by measuring the amount of time that it took for the mouth to open to its maximum point. In the yawn events, this took more than half the time that the mouth was open. This study showed that during the 2nd and 3rd trimester that yawning could be seen frequently in 4D obstetric ultrasound screening.
Scientists still do not quite understand why adults, much less babies, yawn. While in adults, the act of yawning is contagious, babies never seem to be affected. In a study published in 1999 in the Journal of Ultrasound Obstetrics and Gynecology, study information was given that showed that preemies yawn more than full-term babies do.
While the researchers who conducted these studies believe that yawning may be linked to brain maturation and could be used as a health indicator for fetuses, not everyone is on board with this belief. Experts who disagree with the concrete conclusion of the study feel that suggesting yawning is a sign of health in a fetus is too premature. Their argument is presented with the fact that healthy fetuses do yawn.
While the pure definition of a yawn is the involuntary intake of air, this same definition cannot be applied to the fetus who does not breathe air. Further studies must be conducted for a full understanding of just how and why fetuses yawn and what information can be gleaned from the act.