Do Human Fetuses Form Long-Lasting Chemosensory Memories? Longitudinal Follow-Up From Fetus to Young Child of Facial Responses to Flavor/Odor Stimuli.

Prenatal flavor exposure is known to provide the foundation for later flavor or odor preferences in humans, yet the persistence of fetal flavor/odor memories into early childhood remains unclear. In previous studies, fetuses at 32- and 36 weeks gestation were shown to display discriminative facial reactions following a single-dose flavor stimulation (bitter kale vs. non-bitter carrot), and repeated exposure to these flavors from 36 weeks until birth was associated with responses to flavor-specific odors in the first postnatal month. The current longitudinal follow-up tested whether the prenatal exposure to two specific flavors results in flavor-specific odor reactions at 3 years of age. Children (n = 12) who had participated in the fetal and neonatal phases of the study were tested at 3 years of age using controlled olfactory presentations of the same flavors. Results showed that the 3-year-olds exhibited a significantly reduced rate of negative facial expressions in response to the odor they had been repeatedly exposed to in utero (p < 0.001), indicating continuity from prenatal sensory experience to early childhood behavioral responses. Thus, flavor exposure in late gestation can result in long-lasting flavor/odor memory, confirming that the prenatal chemosensory environment can shape behavioral tendencies years after birth.