Researchers in England have been using 4D ultrasound technology to study developing babies as they yawn in the womb.
Nadja Reissland of Durham University’s Department of Psychology has been spearheading the research efforts, along with professors from Lancaster University. While there is a consensus that babies hiccup and swallow in the womb, there has been disagreement about whether or not the mouth movements that have been observed are really yawning.
Riessland says that after studying 15 babies between 24 and 36 weeks gestation, she has clearly been able to distinguish general mouth movements from yawning. However, she believes that the yawning serves a different purpose.
“Unlike us, fetuses do not yawn contagiously, nor do they yawn because they are sleepy,” Reissland said. “Instead, the frequency of yawning in the womb may be linked to the maturing of the brain early in gestation.”
“Given that the frequency of yawning in our sample of healthy fetuses declined from 28 weeks to 36 weeks gestation, it seems to suggest that yawning and simple mouth opening have this maturational function early in gestation,” she added.
The research was explained further in an article written by Reissen, along with co-researchers Brian Francis and James Mason in the publican Plos One.
“Video recordings were made of the fetal face and upper torso visualized by means of 4D full frontal or facial profile ultrasound recordings. Fifteen healthy fetuses were scanned four times at 24, 28, 32 and 36 weeks gestation,” the article states. “For both yawns and simple mouth openings, a smooth varying age effect was significant. The number of yawns observed declined with age from 28 weeks gestation, whereas simple mouth openings were less frequent and the decline was observed from 24 weeks. Gender was not significant either for yawn and simple mouth openings.”
Researchers in the United States have likewise been using ultrasound technology to study the development and movements of babies in the womb.