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Babies Can React to Taste and Smell in the Womb, Study Suggests

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A group of researchers has gathered the first direct evidence that fetuses react in different ways to various tastes and smells. The study is published in Psychological Science.

Can different flavors influence fetal facial expressions?

Adult humans can perceive flavors through a combination of our smell and taste senses. For fetuses, this is thought to occur through ingesting amniotic fluid, either via swallowing or inhalation. The researchers believe that foods consumed during pregnancy may have an effect on babies’ responses to different tastes and flavors once they are born and could even influence the building of healthy eating habits later in life.

To investigate this hypothesis, the team of researchers from Durham University, Aston University and the University of Burgundy enrolled 100 pregnant women into their study. They used 4D ultrasound technology to analyze the facial expressions of fetuses when they were exposed to different flavors of foods eaten by their mother.

What is a 4D ultrasound?

3D ultrasounds render images of internal structures and anatomy as static 3D images, and 4D ultrasounds use these 3D images to produce live-streaming video. This allows clinicians to examine the motion of tissues and organs such as the heart wall, blood vessels and valves.

A bitter pill to swallow

Pregnant women at both 32 and 36 weeks of gestation between the ages of 18 and 40 were given single capsules containing 400 mg of either kale or carrot powder. The capsules were taken approximately 20 minutes before their 4D ultrasound scan, and they were instructed not to consume any food or drink containing these flavors that day.

The results showed that exposure to even small amounts of either kale or carrot flavor could induce a reaction when comparison to control groups that did not receive either flavor. Scans showed that fetuses made more “laughter-face” expressions in response to carrot flavors, and “cry-face” expressions in response to kale.

“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,” explained lead author Beyza Ustun, postgraduate researcher in the Fetal and Neonatal Research Lab at Durham University. “As a result, we think that this repeated exposure to flavors 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.”

The results of this study may have implications on our understanding of the development and function of our taste and smell receptors. Additionally, the authors explain that these findings may inform guidance given to parents during pregnancy surrounding healthy diets and the importance of different tastes.

Study co-author and head of the Fetal and Neonatal Research Lab Professor Nadja Reissland elaborated: “Previous research conducted in my lab has suggested that 4D ultrasound scans are a way of monitoring fetal reactions to understand how they respond to maternal health behaviors such as smoking, and their mental health including stress, depression and anxiety. This latest study could have important implications for understanding the earliest evidence for fetal abilities to sense and discriminate different flavors and smells from the foods ingested by their mothers.”

Can exposure to flavors in utero influence our tastes?

Now, the team is conducting a follow-up study including these babies after their birth to investigate how flavors experienced in the womb can influence their acceptance of different foods. “It could be argued that repeated prenatal flavor exposures may lead to preferences for those flavors experienced postnatally. In other words, exposing the fetus to less ‘liked’ flavors, such as kale, might mean they get used to those flavors in utero. The next step is to examine whether fetuses show less ‘negative’ responses to these flavors over time, resulting in greater acceptance of those flavors when babies first taste them outside of the womb,” explained co-author Professor Jackie Blissett, professor of psychology at Aston University.

Reference: Ustun B, Reissland N, Covey J, Schaal B, Blissett J. Flavor sensing in utero and emerging discriminative behaviors in the human fetus. Psychol Sci. 2022:09567976221105460. doi: 10.1177/09567976221105460

This article is a rework of a press release issued by Aston University. Material has been edited for length and content.