A 4D ultrasound scan shows a foetus yawning in the womb at
24 weeks, during a study by Durham and Lancaster
Universities. REUTERS/Dr Nadja Reissland/handout
Growing into a fully formed human being is a long
process, and scientists have found that unborn babies not only
hiccup, swallow and stretch in the womb, they yawn too.
Researchers who studied 4D scans of 15 healthy foetuses also
said they think yawning is a developmental process which
could potentially give doctors a new way to check on a baby's
While some scientists have previously suggested that foetuses
yawn, others disagree and say it is nothing more than a
developing baby opening and stretching its mouth.
But writing in the journal PLOS ONE on Wednesday, British
researchers said their study was able to clearly distinguish
yawning from "non-yawn mouth opening" based on how long the
mouth was open.
The researchers did this by using 4D video footage to examine
all the times when foetuses opened their mouths.
Nadja Reissland of Durham University's department of
Psychology, who led the study, said the function and
importance of yawning in foetuses is still unknown, but the
findings suggest it may be linked to foetal development and
could provide a further indication of the health of the
"Unlike us, foetuses do not yawn contagiously, nor do they
yawn because they are sleepy," she said. "Instead, the
frequency of yawning in the womb may be linked to the
maturing of the brain early in gestation."
The study was carried out on eight female and seven male
foetuses from 24 to 36 weeks gestation. The researchers found
that yawning declined from 28 weeks and that there was no
significant difference in how often boys and girls yawned.