Babies may be able to sense their mother yawning while they are in the womb, a new study suggests. The findings clarify how fetuses respond to cues from their mother and her external environment early in development.
Existing evidence shows that while in the womb, babies develop the ability to hear and react to internal and external sounds, taste flavors in their mother’s diet, and feel and respond to external touch. At later stages of development, fetuses can also move around, hiccup and yawn—an experience that any pregnant person will tell you feels weird but that also has important developmental implications.
In the new study, the researchers wanted to find out if human fetuses can “catch” yawns from their mother, just as people cause one another to yawn outside the womb. Yawns are physiological responses to tiredness, but they are socially contagious—when we see or hear a person nearby yawn, we tend to yawn, too, regardless of how tired we are. To that end, the team examined 38 pregnant women and found that when the participants yawned, their fetuses tended to yawn soon after; women who yawned more also carried fetuses that yawned more.
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“These findings challenge the view of fetal behavior as purely reflexive or entirely self-contained,” the authors write in the study. Instead the results suggest that fetuses’ behavior reflects the “biological context” they share with their mother, the researchers write.
It’s possible that fetuses develop this yawn response as part of their broader social and attentional growth, the researchers argue. The findings, published on Tuesday in Current Biology, could help reveal how maternal behavior shapes social development both in the womb and after birth.