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| Ultrasound videos have captured fetuses yawning in the womb. |
Even fetuses yawn, a new study shows. During the
second and third trimester, fetuses yawn frequently, and those yawns can be
distinguished in four-dimensional ultrasounds from other mouth-opening
behaviors. As the fetuses mature, they seem to yawn less frequently, the
researchers added. The findings, published Nov. 21 in the journal PLoS One,
suggest yawning patterns of the fetus across pregnancy could be used to assess
whether a growing fetus is developing normally. Scientists don't know why
adults, let alone babies, yawn, said study co-author Nadja Reissland, a
developmental psychologist at Durham University in the United Kingdom.
But yawning behavior changes throughout life.
Yawns in adults are contagious, but babies don't catch them. Anemic babies yawn more
in utero than healthy ones, according to a 1999 study detailed in the journal
Ultrasound Obstetrics and Gynecology. And premature babies yawn more than
full-term babies. (Previous research has shown that as fetuses develop, their facial expressions in the womb become more complex.) That led Reissland to wonder
whether yawning patterns could be an early marker of healthy development that
could be seen even in utero.
While doctors frequently capture ultrasound images of
open-mouthed fetuses, those scans couldn't distinguish yawning from reflexive
mouth opening that prepares the baby to breast-feed, Reissland told
LiveScience. To do so, the team the team took three dimensional ultrasound videos of seven female and eight male fetuses once a month, as
they grew from 24 weeks to 36 weeks gestation (roughly five months to eight
months into pregnancy).
The babies-to-be yawned about six times an hour at 24 weeks, but yawning waned
over the 12-week period and had stopped by 36 weeks. A 3D-ultrasound video
produces 4D-ultrasound images, as the fourth dimension is time.
Reissland and her colleagues are unsure of fetal
yawning's function, though they say it is not a sign of sleepiness. Rather,
because the scans suggest yawning follows a predictable trajectory over fetal
development, the behavior may be linked to brain development early in
gestation, said Reissland. "In fact, yawning might be a trigger for brain
maturation," she told LiveScience. "Ultimately, it could be used in
medical practice. If you see a fetus yawning a lot, there might be some
problem."
Source: Live Science
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