Weanling Infants Prefer the Odors of Green Vegetables, Cheese, and Fish When Their Mothers Consumed These Foods During Pregnancy and/or Lactation

Flavor learning and memory in utero as assessed through the changing pattern of olfactory responses from fetal to neonatal life

Mammalian chemosensory experience begins in utero, where fetuses are exposed to odors and tastes from the mother's diet. Although the effects of prenatal flavor exposure in humans have been investigated postnatally in infant behaviors, longitudinal follow-up studies of fetal and neonatal responses are lacking. To address this, we compared fetal and neonatal facial reactions to specific odors by asking mothers to consume a single calorie-controlled encapsulated dose of powdered kale (n = 14) or a carrot (n = 18) before 4D ultrasound scans at 32 and 36 gestational weeks. Following the 36-week scan, mothers consumed the capsules daily for three consecutive weeks. Results indicated that neonates (mean age = 3.06 weeks) showed a decreased frequency of cry-face, and an increased frequency of laughter-face gestalts in response to the odor stimulus experienced prenatally, regardless of associated taste profile (bitter or non-bitter). These results suggest that repeated chemosensory experience in utero can reduce the aversive hedonic responses of fetuses and shape postnatal memory of the in utero experienced odor. This suggests that prenatal chemosensory mechanisms may have the potential to promote healthy eating habits after birth.

Olfactory testing in infants with perinatal asphyxia: Enhancing encephalopathy risk stratification for future health outcomes

Perinatal asphyxia (PA) is a leading cause of neonatal morbidity and mortality, often resulting in long-term neurodevelopmental challenges. Despite advancements in perinatal care, predicting long-term outcomes remains difficult. Early diagnosis is essential for timely interventions to reduce brain injury, with tools such as Magnetic Resonance Imaging, brain ultrasound, and emerging biomarkers playing a possible key role. Olfaction, one of the earliest senses to develop, may provide valuable insights into long-term neurodevelopmental outcomes following PA due to its intricate neural connections with regions responsible for memory, emotion, and homeostasis. Newborns demonstrate early olfactory abilities, such as recognizing maternal odors, which are vital for bonding, feeding, and emotional regulation. These responses are processed by a network of brain regions, including the olfactory bulb (OB), piriform cortex, amygdala, and orbitofrontal cortex. Hypoxic injury to these regions, particularly the OB, may disrupt olfactory processing in infants with PA, potentially affecting their cognitive and social development. Investigating the relationship between olfactory system development and perinatal brain injury could lead to innovative diagnostic and therapeutic approaches. Further research, including clinical and animal studies, is necessary to fully explore the potential of olfactory assessments in predicting outcomes after PA. This educational review explores and discusses the potential of olfaction as a predictor of long-term outcomes and a tool for risk stratification following PA, opening new pathways for interventions and improved care.

Does Maternal Diet Influence Future Infant Taste and Odor Preferences? A Critical Analysis

The dietary choices a mother makes during pregnancy offer her developing fetus its earliest exposure to the family's culinary preferences. This comprehensive literature review synthesizes five decades of research, which has provided valuable insights into fetal flavor learning. Converging evidence across various species supports the functionality of fetal chemoreceptive systems by the end of gestation, enabling the detection of an extensive array of chemosensory cues derived from the maternal diet and transmitted to the amniotic fluid. The fetus effectively encodes these flavors, resulting in their enhanced acceptance after birth. While existing studies predominantly concentrate on fetal learning about odor volatiles, limited evidence suggests a capacity for learning about gustatory (i.e., taste) properties. Examining whether these prenatal odor, taste, and flavor experiences translate into enduring shifts in dietary behaviors beyond weaning remains a crucial avenue for further investigation.

Maternal Preconception Body Mass Index and Early Childhood Nutritional Risk

BACKGROUND

Risk factors for problematic child eating behaviors and food preferences are thought to begin during the preconception period. It is unknown if maternal preconception body mass index (BMI) is associated with child nutritional risk factors (eg, poor dietary intake and eating behaviors).

OBJECTIVES

We aimed to determine whether maternal preconception BMI was associated with child nutritional risk.

METHODS

In this longitudinal cohort study, a secondary data analysis of children ages 18 mo to 5 y were recruited from The Applied Research Group for Kids (TARGet Kids!), a primary care practice-based research network in Canada. The primary exposure was maternal preconception BMI. The primary outcome was parent-reported child nutritional risk score, measured using the Nutrition Screening for Every Preschooler/Toddler (NutriSTEP), an age-appropriate validated questionnaire. Fitted linear mixed effects models analyzed associations between maternal preconception BMI and child nutritional risk after adjusting for covariates.

RESULTS

This study included 4733 children with 8611 repeated NutriSTEP observations obtained between ages 18 mo to 5 y. The mean (standard deviation [SD]) maternal preconception BMI was 23.6 (4.4), where 73.1% of mothers had a BMI ≤24.9 kg/m2, and 26.9% had a BMI ≥25 kg/m2. The mean (SD) NutriSTEP total score was 13.5 (6.2), with 86.6% at low risk (score <21) and 13.4% at high risk (score ≥21). Each 1 unit increase in maternal preconception BMI was associated with a 0.09 increase in NutriSTEP total score (95% confidence interval [CI]: 0.05, 0.12; P ≤ 0.001). After stratification, each 1 unit increase in maternal BMI was associated with a 0.06 increase in mean NutriSTEP total score (95% CI: 0.007, 0.11; P = 0.025) in toddlers and 0.11 increase in mean NutriSTEP total score (95% CI: 0.07, 0.15; P < 0.001) in preschoolers.

CONCLUSION

Higher maternal preconception BMI is associated with slightly higher NutriSTEP total scores. This provides evidence that the preconception period may be an important time to focus on for improving childhood nutrition. This study was registered at clinicaltrials.gov as NCT01869530.

Chemosensory continuity from prenatal to postnatal life in humans: A systematic review and meta-analysis

Throughout pregnancy, fetuses are exposed to a range of chemosensory inputs influencing their postnatal behaviors. Such prenatal exposure provides the fetus with continuous sensory information to adapt to the environment they face once born. This study aimed to assess the chemosensory continuity through a systematic review and meta-analysis of existing evidence on chemosensory continuity from prenatal to first postnatal year. Web of Science Core. Collections, MEDLINE, PsycINFO, EBSCOhost ebook collection was searched from 1900 to 2021. Studies identified from the search were grouped according to type of stimuli the fetuses were exposed to prenatally that the neonatal infants' responses to were being evaluated, namely flavors transferred from the maternal diet, and the odor of their own amniotic fluid. Of the 12 studies that met the eligibility criteria for inclusion (k = 6, k = 6, respectively in the first and the second group of studies), and eight studies (k = 4, k = 4, respectively) provided sufficient data suitable for meta-analysis. Infants, during their first year of life, oriented their heads for significantly longer durations in the direction of the prenatally experienced stimuli with large pooled effect sizes (flavor stimuli, d = 1.24, 95% CI [0.56, 1.91]; amniotic fluid odor, d = 0.853; 95% CI [.632, 1.073]). The pooled effect size for the duration of mouthing behavior was significant in response to prenatal flavor exposure through maternal diet (d = 0.72; 95% CI [0.306, 1.136]), but not for the frequency of negative facial expressions (d = -0.87, 95% CI [-2.39, 0.66]). Postnatal evidence suggests that there is a chemosensory continuity from fetal to the first year of postnatal life.

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

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.

Maternal Diet During Pregnancy and Lactation and Child Food Preferences, Dietary Patterns, and Weight Outcomes: a Review of Recent Research

PURPOSE OF REVIEW

Efforts to promote children's preferences for healthy foods hold much potential for improving diet quality and preventing obesity. The purpose of this review was to summarize recent evidence for associations between maternal diet during pregnancy and lactation and child food preferences, dietary patterns, and weight outcomes.

RECENT FINDINGS

Recent research illustrates greater maternal vegetable intakes during pregnancy and lactation predict greater child preferences for and intakes of vegetables. Recent randomized clinical trials to improve maternal weight outcomes during the perinatal period via behavioral lifestyle interventions that included dietary components have yielded mixed findings for effects on child weight outcomes. There is strong evidence that maternal diet during pregnancy and lactation shapes flavor preferences during infancy; more research is needed to understand factors that facilitate versus hinder the translation of these preferences to later dietary patterns and weight outcomes.

Traditional plant use during lactation and postpartum recovery: Infant development and maternal health roles

ETHNOPHARMACOLOGICAL RELEVANCE

Evidence of phytochemical roles in infant development and maternal recovery offers insights into beneficial functions of traditional plant use during lactation and the postpartum period. Ethnopharmacological research has relevance to global priorities on maternal and child health, to understanding origins and determinants of human self-medication, and for reconciling traditional postpartum practices and mainstream healthcare.

AIM OF THE STUDY

Present emerging evidence, within evolutionary and socio-cultural contexts, on the role of maternal consumption on transfer of phytochemicals into breast milk with impacts on maternal and child health, and on infant development. Establish current state of knowledge and an ethnopharmacological research agenda that is attentive to cross-cultural and regional differences in postpartum plant use.

MATERIALS AND METHODS

An extensive literature review using Medline, Scopus, and Web of Science focused on traditional and contemporary use and socio-cultural context, as well as physiological, pharmacological, toxicological, and behavioral activities of plants used medicinally by women during postpartum recovery and lactation.

RESULTS

The most widely reported postpartum plants show antimicrobial, anti-inflammatory, immunological, and neurophysiological activities, with low toxicity. Phytochemicals transfer from maternal consumption into breast milk in physiological concentrations, while animal studies demonstrate immunomodulation and other actions of medicinal plants during lactation. Reporting on the use and diverse traditional knowledge of women about plants during the postpartum period is obscured by the marginal place of obstetric issues and by gender biases in ethnobotanical research. In many contemporary contexts use is prejudiced by precautionary risk warnings in health literature and practice that confound lactation with pregnancy.

CONCLUSIONS

Although systematic investigation of postpartum plant use is lacking, known pharmacological activities support potential benefits on infant development and maternal health with immediate and long-term consequences in relation to allergic, inflammatory, autoimmune, and other diseases. An ethnopharmacological agenda focused on the perinatal period requires directed methodologies and a regional approach in relation to culturally-specific knowledge and practices, traditional plant use, and local health needs. Testing the hypothesis that phytochemicals transferred from medicinal plants into breast milk impact the human immune system and other aspects of infant development requires extended analysis of phytochemicals in human milk and infant lumen and plasma, as well as effects on gastrointestinal and milk microbiome.

Central Nervous System Processing of Floral Odor and Mother's Milk Odor in Infants

Newborns have a functioning sense of smell at birth, which appears to be highly significant for feeding and bonding. Still, little is known about the cerebral odor processing in this age group. Studies of olfactory function relied mostly on behavioral, autonomic, and facial responses of infants. The aim of the present study was to investigate central odor processing in infants focusing on electroencephalography (EEG)-derived responses to biologically significant odors, namely a food and a non-food odor. A total of 21 term-born, healthy infants participated (11 boys and 10 girls; age range 2-9 months, mean 5.3 ± 2.2 months). Odor stimuli were presented using a computer-controlled olfactometer. Breast milk was used as food odor. Farnesol was presented as a non-food odor. In addition, odorless air was used as a control stimulus. Each stimulus was presented 30 times for 1 s with an interstimulus interval of 20 s. EEG was recorded from 9 electrodes and analyzed in the frequency domain. EEG amplitudes in the delta frequency band differed significantly after presentation of food (breast milk) odor in comparison to the control condition and the non-food odor (farnesol). These changes were observed at the frontal recording positions. The present study indicates that central odor processing differs between a food and a non-food odor in infants. Results are interpreted in terms of focused attention towards a physiologically relevant odor (breast milk), suggesting that olfactory stimuli are of specific significance in this age group.

Olfaction scaffolds the developing human from neonate to adolescent and beyond

The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.