29 September 2022
Scientists have recorded the first direct evidence that babies react differently to various smells and tastes while in the womb by looking at their facial expressions.
A study which included researchers from Aston University took 4D ultrasound scans of 100 pregnant women to see how their unborn babies responded after being exposed to flavours from foods eaten by their mothers.
Researchers looked at how the fetuses reacted to either carrot or kale flavours just a short time after the flavours had been ingested by the mothers.
Fetuses exposed to carrot showed more “laughter-face” responses while those exposed to kale showed more “cry-face” responses.
Their findings could further our understanding of the development of human taste and smell receptors.
The researchers also believe that what pregnant women eat might influence babies’ taste preferences after birth and potentially have implications for establishing healthy eating habits.
The study - led by Durham University’s Fetal and Neonatal Research Lab - is published in the journal Psychological Science.
Humans experience flavour through a combination of taste and smell. In fetuses, it is thought that this might happen through inhaling and swallowing the amniotic fluid in the womb.
The research team, which also included scientists from Aston University, Birmingham, and the National Centre for Scientific Research-University of Burgundy, France, scanned the mothers, aged 18 to 40, at both 32 weeks and 36 weeks of pregnancy to see fetal facial reactions to the kale and carrot flavours.
Mothers were given a single capsule containing approximately 400mg of carrot or 400mg kale powder around 20 minutes before each scan. They were asked not to consume any food or flavoured drinks one hour before their scans.
The mothers also did not eat or drink anything containing carrot or kale on the day of their scans to control for factors that could affect fetal reactions.
Facial reactions seen in both flavour groups, compared with fetuses in a control group who were not exposed to either flavour, showed that exposure to just a small amount of carrot or kale flavour was enough to stimulate a reaction.
Lead researcher Beyza Ustun, a postgraduate researcher in the Fetal and Neonatal Research Lab, Department of Psychology, Durham University, said: “A number of studies have suggested that babies can taste and smell in the womb, but they are based on post-birth outcomes while our study is the first to see these reactions prior to birth.
“It was really amazing to see unborn babies’ reaction to kale or carrot flavours during the scans and share those moments with their parents.”
Research co-author Professor Jackie Blissett, of Aston University, said: “It could be argued that repeated prenatal flavour exposures may lead to preferences for those flavours experienced postnatally. In other words, exposing the fetus to less ‘liked’ flavours, such as kale, might mean they get used to those flavours in utero.
“The next step is to examine whether fetuses show less ‘negative’ responses to these flavours over time, resulting in greater acceptance of those flavours when babies first taste them outside of the womb.”