Flavor Sensing in Utero and Emerging Discriminative Behaviors in the Human Fetus

Abstract

The diet of pregnant women exposes fetuses to a variety of flavors consisting of compound sensations involving smell, taste, and chemesthesis. The effects of such prenatal flavor exposure on chemosensory development have so far been measured only postnatally in human infants. Here, we report the first direct evidence of human fetal responsiveness to flavors transferred via maternal consumption of a single-dose capsule by measuring frame-by-frame fetal facial movements. Pregnant women and their fetuses based in the northeast of England were involved in this study from 32 to 36 weeks’ gestation. Fetuses exposed to carrot flavor ( n = 35) showed “lip-corner puller” and “laughter-face gestalt” more frequently, whereas fetuses exposed to kale flavor ( n = 34) showed more “upper-lip raiser,” “lower-lip depressor,” “lip stretch,” “lip presser,” and “cry-face gestalt” in comparison with the carrot group and a control group not exposed to any flavors ( n = 30). The complexity of facial gestalts increased from 32 to 36 weeks in the kale condition, but not in the carrot condition. Findings of this study have important implications for understanding the earliest evidence for fetal abilities to sense and discriminate different flavors.

Why human olfaction should not be modeled on theories and tasks of vision

“…In everyday life, incidental learning is much more important than intentional learning, especially in odor and taste memory where people are never asked to learn intentionally. Incidental learning is responsible for (food) preference formation and thereby for much of eating behavior ( Schaal et al, 1998 ; Mennella et al, 2001 ; Hausner et al, 2010 ; Remy et al, 2013 ; Hetherington et al, 2015 ; Nicklaus and Schwartz, 2019 ; Ustun et al, 2022 ).…”

“…The formation of food preferences is initiated already in the fetal state and continues after birth by repeated exposure to foods. Olfaction plays a key role in flavor perception and is therefore important in forming the memories constituted by food preferences, which are in many aspects implicit in nature ( Schaal et al, 1998 , 2000 ; Hausner et al, 2010 ; Hetherington et al, 2015 ; Nicklaus and Schwartz, 2019 ; Ustun et al, 2022 ).…”

Why have a bottle when you can have draught? Exploring bottle refusal by breastfed babies

“…The potential link between 'dummy refusal' and bottle refusal provides an intriguing insight into bottle refusal being attributed to physical sensation for some babies. Childhood rejection of foods owing to a heightened sensitivity to taste and texture is suggested by Russell andWorsley (2013), andCappellotto andOlsen (2021), and a recent study by Ustun et al (2022) has shown that the fetus can respond negatively to certain tastes while in utero. The fact that mothers in our study reported their baby refusing both expressed breastmilk and formula in a bottle and cup indicates that 'taste' does not appear to be implicated in refusal.…”

Biological and behavioral pathways from prenatal depression to offspring cardiometabolic risk: Testing the developmental origins of health and disease hypothesis.

“…D. Barker et al, 2013), which could affect the nutrients received and flavors the fetus is exposed to in utero and alter subsequent food intake in offspring (Lesage et al, 2004; Paternain et al, 2012). There is evidence that flavors ingested by the mother are transmitted to offspring through amniotic fluid (Mennella, 2014) and that fetuses are differentially responsive to unique flavors (specifically sweet and bitter flavors) in utero (Ustun et al, 2022). Foods ingested during pregnancy or during the lactation period are more likely to be accepted by infants around 6 months of age (Mennella, 2014), suggesting that diet of the mother during pregnancy may lay the foundation for the child’s dietary preferences.…”