Fetus Yawning Reveals Brain Development

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.