Child Psychology. Jean-Pascal Assailly

      2.6.4. Exposure to acrylamide

      Acrylamide is a known neurotoxin to humans and animals and has been classified as “probably carcinogenic” in humans. It does not occur naturally and has been produced since the 1950s for use, for example, in water and wastewater treatment, as gels in laboratories, or in tile grout. In these cases, the main routes of occupational exposure are inhalation and epidermis. Acrylamide is also found in cigarette smoke and diet is the primary source of acrylamide exposure in non-smokers. Acrylamide crosses the placental barrier.

      In the EDEN study, dietary acrylamide intake during pregnancy was assessed by combining maternal food frequency questionnaires with data on food contamination nationally, provided by the second French Total Diet Study. The study showed a relationship between increased maternal exposure to acrylamide and fetal growth, both in weight and length.

      2.6.5. Cadmium exposure

Cadmium is a metal found in batteries, pigments and plastics; its toxicity on health is known (bone disease, certain cancers); exposure can come from two sources, food and tobacco use, and its percentage through ingestion can increase during pregnancy.

      In the EDEN study, blood cadmium concentration was associated with fetal growth restriction and low birth weight; the strong association between cadmium and tobacco use indicates that blood cadmium concentration may be a good biomarker of tobacco toxicity on fetal development.

      2.6.6. Exposure to caffeine

      Data from animal studies suggest that maternal caffeine consumption during pregnancy has adverse effects on the subsequent brain development of the offspring. However, human data in this area is limited.

      Multivariate modeling was carried out on the EDEN cohort, using data from 1,083 mother–child pairs (Bernard and van der Waerden 2016). Measurements included estimated maternal caffeine intake during pregnancy, child IQ at 5.5 years and individual and family characteristics.

      Prenatal caffeine exposure was common in the sample (91%), with 12% having intakes ≥ 200 mg/day, which is a high intake. There was a significant negative relationship between caffeine intake and child IQ at 5.5 years. In particular, children of mothers consuming ≥ 200 mg/day were more likely to have borderline or lower IQs compared with children of mothers consuming <100 mg/day.

2.7. Microbiota

      The term “microbiota” refers to all the microorganisms that live on us or in us. The intestine is the most densely populated, but other organs such as the skin or the respiratory tract are also home to them.

      So-called new-generation genetic sequencing technologies have improved our knowledge of the microbiota and identified a much larger repertoire (bacteria, fungi, viruses and parasites) than was previously known.

      Thus, some authors suggest that the human being should henceforth be considered as a “holobiont”, that is, a biomolecular ensemble associating the human host with a set of microbes, the whole constituting a single ecological entity.

Several theories attempt to explain the effects of microbiota on the child: hygiene theory assumes an inverse relationship between the frequency of allergic pathologies and exposure to microorganisms (greater circulation of microbes and prevalence of asthma, eczema and urticaria); the “Old Friends” or host-microbiota symbiosis theory assumes that microbial agents associated with the rural, or even ancestral, way of life provide protection against allergic pathologies; Dysbiosis and Biodiversity Loss theory, which assumes that the loss of diversity of the microbiota, favored by the Western lifestyle, leads to a disruption of the balance between microbiota and host, and to perturbations in the immune system leading to the breakdown of tolerance and the appearance of atopic⁴ diseases.

      The first 1,000 days (from conception to the end of the second year) seem to be a very sensitive period for biological influences, such as the microbiota. An undernourished or malnourished microbiota will have long-term consequences on the development of the child and greatly influences the risk of chronic disease. A dialog between the microbiota and the immune system will be established, strongly linked to the environment, to stabilize around the age of three years.

      Various environmental factors influencing the microbiota have been identified: the mother’s diet and prenatal exposures influence the immune system of the newborn and the mode of delivery and breastfeeding can also strongly influence the microbiota.

      Thus, the analysis of a newborn’s first stools could reveal certain clues about the risk of obesity at the age of three years. This prediction is based on the nature of the bacterial species in the gut. The first stool, or meconium, is essentially composed of material ingested during intrauterine life.

      Similarly, the administration of antibiotics to newborns alters the microbiota. Thus, babies who receive antibiotics during their first year have a smaller actinobacteria population at age one than those who received an antibiotic just after birth, or whose mothers used antibiotics during pregnancy and, of course, those who did not receive antibiotics at all.

      1 1 IVF = in vitro fertilization and DAI = donor-assisted insemination.

      2 2 The functioning of this system will be described later in the chapter on emotions.

      3 3 To overcome the lack of precision of routine food health surveillance, total diet studies (TDSs) are national cross-sectional surveys designed to analyze a large number of substances in defined food samples to be representative of the diet of the study population. They are based on food surveys. TDSs allow the identification of substances for which there is a risk of excess in the population and the food vectors contributing most to exposures (Traoré et al. 2018).

      4 4 Atopy is a genetic predisposition to the cumulative development of common allergies.