Babies React to Tastes and Smells in the Womb

Scientists have found the first direct evidence that babies in the womb react differently to different smells and tastes based on their facial expressions. A study led by the Fetal and Neonatal Research Lab at Durham University in the UK used 4D ultrasound images of 100 pregnant women to investigate how their unborn babies reacted to the aromas of foods their mothers had eaten. The researchers observed how the fetuses reacted to the taste of carrots or kale shortly after their mothers had ingested the aromas. The study was published in the journal Psychological Science.

Fetuses exposed to carrots showed more “smiling face reactions,” while those exposed to kale showed more “crying face reactions.” Their findings could deepen our understanding of the development of human taste and smell receptors. The researchers also believe that the diet of pregnant women influences the taste preferences of babies after birth and could potentially have an impact on the development of healthy eating habits.

How Unborn Babies React to the Taste of Different Foods Consumed by their Mothers

Humans perceive taste through a combination of tasting and smelling. In fetuses, this is believed to occur through inhalation and swallowing of amniotic fluid in the womb. Lead researcher Beyza Ustun, a PhD student at the Fetal and Neonatal Research Lab in the Department of Psychology at Durham University, said: “A number of studies have shown that babies can taste and smell in the womb, but these studies are based on postnatal findings, whereas our study looks at the first reactions before birth. We therefore believe that this repeated exposure to flavors before birth may contribute to the development of food preferences after birth, which could be important when it comes to conveying information about healthy eating and possibly avoiding “picky eating behavior” during weaning. It was truly amazing to see the reactions of unborn babies to the taste of kale or carrots during the ultrasound scans and to share these moments with their parents.”

The research team, which also included scientists from Aston University in Birmingham (UK) and the National Center for Scientific Research at the University of Burgundy (France), studied mothers aged 18 to 40 in their 32nd and 36th weeks of pregnancy to observe the facial reactions of their fetuses to the taste of kale and carrots. The mothers were given a capsule containing approximately 400 mg of carrot or 400 mg of kale powder about 20 minutes before each scan. They were asked not to eat any food or drink any flavored beverages for one hour before the scans. The mothers also did not eat or drink anything containing carrots or kale on the day of the test to rule out factors that could influence the fetuses’ reactions.

Acceptance of Different Flavors After Birth

The facial reactions observed in both flavor groups showed that, compared to fetuses in a control group that were not exposed to either flavor, even a small amount of carrot or kale flavor was enough to trigger a reaction. Co-author Professor Nadja Reissland, head of the Fetal and Neonatal Research Lab at Durham University’s Department of Psychology, supervised Beyza Ustun’s research. She said: “Previous research in my lab has shown that 4D ultrasound scans are a way to observe fetal responses to understand how they react to maternal health behaviors such as smoking and their mental health, including stress, depression, and anxiety. This study could provide important insights into understanding the earliest signs of the ability of fetuses to perceive and distinguish different flavors and odors of foods consumed by their mothers.

Co-author Professor Benoist Schaal from the National Center for Scientific Research at the University of Burgundy, France, said: “Based on the facial reactions of the fetuses, we can assume that a range of chemical stimuli enter the fetal environment via the mother’s diet. This could have important implications for our understanding of the development of our taste and smell receptors and the associated perception and memory.” The researchers say their findings could also help educate mothers about the importance of taste and a healthy diet during pregnancy. They have begun a follow-up study with the same babies after birth to investigate whether the flavors they perceived in the womb influence their acceptance of different foods. According to study co-author Professor Jackie Blissett of Aston University, babies may become accustomed to these flavors while still in the womb. The next steps are to investigate whether fetuses show fewer “negative” reactions to these flavors over time, leading to greater acceptance of these flavors when babies try them for the first time outside the womb.