According to a new study of around 100 pregnant women and their fetuses in England, babies in the womb smiled after they ate carrots but scowled after their moms ate kale.
The study offers a rare glimpse at how fetuses respond to flavors in real-time. The researchers gave the participating pregnant women capsules that contained powdered versions of the two foods.
A total of 35 women consumed the equivalent of one medium carrot, while 34 women consumed the equivalent of 100 grams of chopped kale. The remaining 30 women did not eat either carrots or kale.
Ultrasound shows most fetuses exposed to carrot appeared to be laughing
Ultrasound scans showed 20 minutes later that most fetuses exposed to the carrot appeared to be laughing while most exposed to the kale flavor seemed to grimace. The control group that participated in the study did not have the same responses.
Nadja Reissland, a co-author of the study and the head of the Fetal and Neonatal Research Lab at Durham University, said that they are the first ones to show the facial expressions in relation to the food which the mother has just consumed on an ultrasound scan.
Previous research has revealed that the amniotic fluid surrounding a fetus can have different flavors or smells depending on the diet of a pregnant person. A study conducted in 2001 also found that infants exposed to the taste of carrots through breast milk or amniotic fluid showed fewer negative facial expressions in reaction to carrot-flavored cereal than infants who had not had those previous exposures.
That study, however, examined infants' responses only outside the womb. The fetuses participating in the new research were at 32 to 36 weeks gestation. Reissland said the images from the ultrasound suggest reactions similar to those of children or adults who taste something bitter. But it is not known whether fetuses actually experience dislikes or emotions in a similar manner.
Fetuses known to make facial expressions
Reissland added that the grimaces in the ultrasounds might be just the muscle movements of the fetuses, which are reacting to a bitter flavor. She noted that fetuses are known to make facial expressions, though. According to Reissland, fetuses' expressions become more and more complex if you look at it from 24 to 36 weeks gestation.
Dr. Daniel Robinson, an associate professor of neonatology at Northwestern University Feinberg School of Medicine, offered a similar caution, telling NBC News that people should not interpret the ultrasound images as showing the happiness or distaste of the fetuses.
Robinson, who was not involved in the new research, did note that there is the notion that infants and newborns will have a preference for sweeter flavors. He said there are evolutionary ideas behind that thinking.
