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Despite a 15-year long effort to define the "safety" of fish intake during pregnancy, there remains still uncertainty on this important public health issue. The evaluation of the toxic effects of contaminants, particularly mercury (Hg) in fish-eating populations is complicated by the fact that sea-food is also rich in beneficial nutrients, such as selenium (Se). There is toxicological plausibility of an antagonistic effects between Se and Hg, and some theoretical support for the inclusion of the Se-Hg interaction to better assess the risk linked with fish intake. To assess the effects of exposure to low-level Hg through fish consumption on the developing brain and the interaction between Hg and Se, we conducted an analysis at age 40 months in Italian children, enrolled in a prospective mother-child cohort, comparing additive and multiplicative models. Participant subjects were the 470 children born within the Northern Adriatic Cohort II (NAC-II) cohort who were tested by using the Bayley Scales of Infant and Toddler Development third edition (Bayley-III) (BSID-III) at age 40. Family demographic and socioeconomic information, pregnancy and delivery history, parental and child medical history and food consumption were assessed through questionnaires. Maternal blood samples were collected during pregnancy, cord blood at birth and maternal milk 1 month after delivery. As other exposures of interest, we considered the level of Se in maternal and cord blood and in breast milk and the potential Se-Hg antagonism. Se and inverse of THg (1:THg) concentrations were categorized according to the tertiles of their distributions, in low, medium and high levels of exposure. The lower end of the composite cognitive score distribution closest to 20% was defined as suboptimal development. Multiple logistic regression were applied to assess the association between the dichotomized composite cognitive score and the categorized exposure to Se and 1:THg, and the antagonism between Se and 1:THg. In the recruiting period, 900 pregnant women were enrolled in the cohort; 767 of these remained in the study at delivery and 470 children at 40 months. After excluding preterm births, 456 children were used in the final analyses. The larger difference in risk for suboptimal neurodevelopment was observed for the category with High THg and Low Se with OR = 2.55 (90% CI 1.02; 6.41) under the multiplicative and OR = 1.33 (90% CI 0.80; 1.87) under the additive model. The category High THg and High Se showed a very slightly better fit of the additive model (OR = 1.07, 90% CI 0.65; 1.50) versus the multiplicative (OR = 1.66, 90% CI 0.73; 1.77). A negative - antagonistic - interaction term for this category was estimated under the multiplicative model giving an OR = 1.17 (90% CI 0.42; 3.28). Although this evidence of the effects of the Se-Hg antagonism on the children neuro-development needs to be confirmed, if Se can counterbalance Hg toxicity, the evaluation of the effect on human health of fish consumption, should also consider the diverse ratios between Se and Hg concentration in different fish species., (Copyright © 2020 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Introduction: Neurotoxicity due to acute prenatal exposure to high-dose of mercury (Hg) is well documented. However, the effect of prenatal exposure to low Hg levels on child neurodevelopment and the question about "safety" of fish-eating during pregnancy remain controversial. International comparisons of Hg concentrations in mother-child biological samples and neurodevelopmental scores embedded in birth cohort studies may provide useful evidence to explore this issue., Materials and Methods: The Mediterranean (Italy, Slovenia, Croatia, and Greece) cohort study included 1308 mother-child pairs enrolled in the Public Health Impact of long-term, low-level, Mixed Element exposure in a susceptible population EU Sixth Framework Programme (PHIME). Maternal hair and venous blood, cord blood and breast milk samples were collected, and total Hg (THg) levels were measured. Demographic and socioeconomic information, lifestyles and nutritional habits were collected through questionnaires at different phases of follow-up. Children at 18 months of age underwent neurodevelopmental testing using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Multivariate linear and logistic regressions were performed, for each country, to assess the association between THg and BSID-III scores, obtaining adjusted β coefficients and odds ratios (ORs). These values were used to conduct a meta-analysis, to explore possible heterogeneity among countries and to obtain combined estimates of the association between THg exposure and BSID-III scores., Results: Median THg (ng/g) was: 704 in maternal hair, 2.4 in maternal blood, 3.6 in cord blood, and 0.6 in breast milk. THg concentrations were highest in Greece and lowest in Slovenia. BSID-III neurodevelopmental scores were higher in Croatia and Slovenia. The meta-analysis of multivariate linear models found an overall positive association between language composite score and receptive communication scaled score and increasing THg in maternal hair (n = 1086; β = 0.55; 95%CI: 0.05-1.05 and n = 1075; β = 0.12; 95%CI: 0.02-0.22, respectively). The meta-analysis of logistic regression models showed that the overall adjusted OR between THg in cord blood and suboptimal gross motor score was borderline significant (n = 882; OR = 1.03; 95%CI: 1.00-1.07). Heterogeneity was found across the four sub-cohorts for language composite score in maternal blood, and for fine motor scaled score in cord blood and breast milk. Language composite score and THg concentrations in maternal venous blood were positively related (n = 58; β = 4.29; CI95% (-0.02, 8.60)) in Croatia and an increase of 1 ng/g of THg in maternal venous blood was associated with a reduced risk for children to fall in the lowest quintile of language score by 31% (n = 58; OR = 0.69; CI 95%: 0.37, 1.01). The comparison of β coefficients obtained by multiple linear regression model showed an inverse association between fine motor score and THg concentrations in cord blood for Croatia (n = 54; β = -0.53; CI 95%: -1.10, 0.04) and Slovenia (n = 225; β = -0.25; CI 95%: -0.49, -0.01). In Slovenia THg level in breast milk was associated with suboptimal fine motor performance (n = 195; OR = 5.25; CI 95%: 1.36, 21.10)., Conclusions: This study showed an inverse relation between THg levels and developmental motor scores at 18 months, although the evidence was weak and partially internally and externally inconsistent. No evidence of detrimental effects of THg was found for cognitive and language outcomes at these concentrations and age., (Copyright © 2018 Elsevier GmbH. All rights reserved.)