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24-week old fetus yawning
Though the precise design of yawning is a mystery story , 4 - D ultrasound images let on that fetuses gape in utero
27-week old fetus
Yawns can be distinguished from feeding reflex action because gape sassing expend longer undecided and have a shorter closing period .
28-week old fetus
As babies mature , they gape less oft . Researchers believe oscitancy may help touch off brain development .
32-week old fetus
Because yawning frequency changes throughout maternity , yawn pattern could be used as a marker of healthy development .
Yawning in utero
By the time babies are full - full term , they have stop yawning in the womb .
Fetal Faces
researcher used ultrasound images of foetus ' faces , like these , to track how they used progressively more complex facial movements .
Ultrasound videos have captured fetuses yawning in the womb.
