Foetuses exposed to carrot showed more “laughter-face” responses, while those exposed to kale showed more “cry-face” reactions.
The study, which is published in the journal Psychological Science, could advance understanding of how human taste and smell receptors develop.
Mothers were scanned at 32 and 36 weeks pregnancy to see foetal facial reactions to the kale and carrot flavours, as part of the research.
They were given a single capsule containing approximately 400mg of carrot or 400mg kale powder around 20 minutes before each scan and avoided eating anything with a flavour for an hour beforehand.
Facial reactions seen in both groups showed that exposure to just a small amount of carrot or kale flavour was sufficient to stimulate a response.
It is thought foetuses experience flavour by inhaling and swallowing amniotic fluid in the womb.
Postgraduate Beyza Ustun, who led the research, 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.
“As a result, we think that this repeated exposure to flavours before birth could help to establish food preferences post-birth, which could be important when thinking about messaging around healthy eating and the potential for avoiding ‘food-fussiness’ when weaning.”
She added: “It was really amazing to see unborn babies’ reaction to kale or carrot flavours during the scans and share those moments with their parents.”
Co-author Professor Nadja Reissland, who heads the Fetal and Neonatal Research Lab, said: “This latest study could have important implications for understanding the earliest evidence for foetal abilities to sense and discriminate different flavours and smells from the foods ingested by their mothers.”
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 foetus to less ‘liked’ flavours, such as kale, might mean they get used to those flavours in utero.
“The next step is to examine whether foetuses 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.”
Additional reporting by SWNS