Skip to main content

Image Gallery: Yawning in the Womb

Ultrasound videos have captured fetuses yawning in the womb. (Image credit: Nadja Reissland)

24-week old fetus yawning

(Image credit: Nadja Reissland)

Though the exact purpose of yawning is a mystery, 4-D ultrasound images reveal that fetuses yawn in utero

27-week old fetus

(Image credit: Nadja Reissland)

Yawns can be distinguished from feeding reflexes because yawning mouths spend longer open and have a shorter closing period.

28-week old fetus

(Image credit: Nadja Reissland)

As babies mature, they yawn less frequently. Researchers believe yawning may help trigger brain development.

32-week old fetus

(Image credit: Nadja Reissland)

Because yawning frequency changes throughout pregnancy, yawn patterns could be used as a marker of healthy development.

Yawning in utero

(Image credit: Wolfgang Moroder)

By the time babies are full-term, they have stopped yawning in the womb.

Fetal Faces

Fetal facial expressions develop in the womb

(Image credit: Nadja Reissland)

Researchers used ultrasound images of fetuses' faces, like these, to track how they used progressively more complex facial movements.