New Study Captures Fetuses' Facial Reactions to Foods
Four-dimensional ultrasound reveals fetuses smile at carrots and cry at kale.
Posted September 26, 2022 | Reviewed by Ekua Hagan
- Food consumed by pregnant women is shared with developing babies. Now scientists can see how faces change in response to food flavors.
- Advances in 4D ultrasound technology allow for better facial images in the womb.
- Researchers found that “laughter-faces” are associated with carrots and “cry-faces” are more frequent with kale.
- Fetuses in the last three months of pregnancy are mature enough to distinguish between different tastes transferred from the maternal diet.
New research suggests that human fetuses can detect food flavors from their mom’s diet and they may not like everything they are getting. Fetuses ranging from 32-36 weeks were exposed to either carrot or kale flavors while their facial reactions were recorded using four-dimensional (4D) ultrasound video. This study is the first to measure frame-by-frame facial movements in response to maternal diet. Fetuses exposed to carrot flavor showed “laughter-face” patterns more frequently, while those exposed to kale flavor showed more “cry-face” patterns. Conclusion: babies like carrots more than kale, and they are not afraid to show it!
Dietary Preferences Start Before Birth
Generations of parents know that some kids just don’t like green vegetables. It can be a real struggle and parents can go to great lengths to incentivize green veggie consumption. For example, kids can be hoodwinked into eating broccoli simply by wrapping it in paper emblazoned with the McDonald’s logo. Until recently, it was unclear just how early this aversion to greens shows up.
Touch is the first sense to emerge in a growing baby. The developing fetus responds to touch of the lips and cheeks usually by 8 weeks and to other parts of its body at 14 weeks. Taste and hearing follow. Some flavors, such as garlic, vanilla, mint, and carrot, are believed to be transmitted into the amniotic fluid, which babies live in and consume. In a test of this, one group of pregnant women drank carrot juice every day during pregnancy while another group avoided it altogether. Once the babies started eating solid food, researchers fed them either water-flavored cereal or carrot juice-flavored cereal. Babies exposed to carrot in amniotic fluid ate more of the carrot-flavored cereal.
Visual Confirmation: Facial Responses in Fetuses
Researchers, armed with the latest 4D ultrasound scanning technology, are now able to capture fetal facial movements with remarkable frame-by-frame clarity. The study examined the healthy fetuses of 100 women between 18 and 40 years of age. Roughly one-third of the women were put into an experimental group that consumed an organic kale capsule, one-third were put into a group that took a carrot capsule, and one-third were put into a control group that was not exposed to either flavor.
To minimize the effect of confounding variables, participants did not eat or drink anything containing carrot or kale on the day of their scans. After consuming the capsules, participants waited 20 minutes followed by 4D ultrasound scans. Results show that fetuses exposed to carrot flavor exhibited “lip-corner puller” and “laughter-face gestalt” more frequently, whereas fetuses exposed to kale flavor demonstrated more “upper-lip raiser,” “lower-lip depressor,” “lip stretch,” “lip presser,” and “cry-face gestalt” movements.
During pregnancy, fetuses are exposed to any number of flavors transferred from the mother consisting of different tastes, smells, and chemical profiles. Before this study, the relationship between prenatal flavor exposure on development had only been evaluated postnatally in infants. These results have consequences for our understanding of how fetuses learn to sense and differentiate flavors.
The Power of Prenatal Tasting
More work is needed to assess how prenatal flavor exposure can exert influences on food preferences across the lifespan. Also, researchers need to examine the impact of cuisines across cultures since the sample of soon-to-be-moms included in the study were all white women from northeast England. It will be interesting to see how fetuses respond in cultures where extra spicy or extra bitter foods play a big role in a country’s culinary patterns. And what about genetic differences in taste sensitivity? Prenatal flavors may influence super-tasters in different ways compared to non-tasters.
©2022 Kevin Bennett Ph.D. All rights reserved.
Ustun, B., Reissland, N., Covey, J., Schaal, B., & Blissett, J. (2022). Flavor Sensing in Utero and Emerging Discriminative Behaviors in the Human Fetus. Psychological Science, 0(0). https://doi.org/10.1177/09567976221105460