Long-chain polyunsaturated fatty acids at birth and cognitive function at 7 y of age

Fatty acids and early human development

Fatty acids play central roles in growth and development through their roles in membrane lipids, as ligands for receptors and transcription factors that regulate gene expression, precursor for eicosanoids, in cellular communication, and through direct interactions with proteins. Adverse fatty acid supplies during fetal and child development alter the fatty acid composition of membrane phospholipids and storage triglycerides with the potential to disrupt cellular environments, and program structure and function. Maternal fatty acid nutrition during pregnancy and lactation determines the transfer of essential n-6 and n-3, and non-essential trans fatty acids via the placenta and through human milk. Poor maternal docosahexaenoic acid (DHA) status increases risk of inadequate DHA to support brain and retinal development, delaying or limiting neural and visual system development. The implications of recent changes in the dietary fatty acids on maternal to infant fatty acid transfer, including the composition of human milk has been insufficiently studied.

The effects of maternal dietary docosahexaenoic acid intake on rat pup myelin and the auditory startle response

We investigated the effects of maternal docosahexanoic acid (DHA) supplementation on pups' auditory startle responses and the composition of brain myelin.

METHODS

Timed-pregnant rats were fed throughout pregnancy and lactation diets that contained 0, 0.3, 0.7 or 3% of total fatty acids as DHA. Milk was collected from culled pups' stomachs on postnatal day (PND) 3, latency of the auditory startle reflex was measured on PND 15, and pups were killed and brains collected on PND 24.

RESULTS

Higher levels of DHA in maternal diet were reflected in milk and in pups' myelin. The latency of the auditory startle response was significantly longer in offspring of dams fed higher levels of DHA. There was a positive correlation between the myelin content of DHA and the latency of the startle response (p = 0.044), and a negative correlation between the myelin content of DHA and the myelin content of cholesterol (p = 0.005).

CONCLUSION

High levels of maternal DHA intake alter the lipid composition of rat pup myelin, and are associated with longer latencies of the auditory startle response--a myelin-dependent electrophysiologic response.

Prenatal and early postnatal fatty acid status and neurodevelopmental outcome

The present review addresses the effect of pre- and postnatal supplementation of nutrition with long-chain polyunsaturated fatty acids (LCPUFA) on neurodevelopmental outcome. The few studies which addressed the effect of prenatal LCPUFA status or prenatal LCPUFA supplementation suggest that a better prenatal arachidonic acid (AA) and doxosahexaenoic acid (DHA) status might be related to a better neurodevelopmental outcome until at least 18 months of age. A review of the few randomized controlled trials on formula supplementation with LCPUFA in preterm infants did not provide evidence for a significant beneficial effect of LCPUFA on developmental outcome. A review of the trials on formula supplementation with LCPUFA in term infants revealed that supplementation with LCPUFA, in particularly supplementation with >or=0.30% DHA, has a beneficial effect on neurodevelopmental outcome until 4 months. The studies could not demonstrate a consistent positive effect beyond that age. It was concluded that the relatively subtle effects of LCPUFA supplementation on neurodevelopmental outcome do not only depend on dosage but also on the gestational period during which the nutritional components are supplied: supplementation prior to term seems to have more effect than that after term.

Effects of n-3 long chain polyunsaturated fatty acid supplementation on visual and cognitive development throughout childhood: a review of human studies

The present paper evaluates the most recent randomized controlled trials assessing the efficacy of n-3 LCPUFA supplementation (with or without n-6 LCPUFA) during pregnancy, lactation, infancy and childhood on visual and cognitive development. Available evidence suggests a beneficial effect of maternal n-3 LCPUFA supplementation during pregnancy and lactation on cognitive development of infants and children, but not for visual development. Evidence for an effect of LCPUFA supplementation of preterm and term infants on cognitive development of infants remains inconclusive. However, supplementing term infants with daily doses of 100 mg docosahexaenoic acid plus 200 mg arachidonic acid improves visual development as measured by electrophysiological tests. Evidence for benefits of n-3 LCPUFA on cognitive development in healthy children older than 2 years of age is too limited to allow a clear conclusion. Taken together, the evidence for potential benefits of LCPUFA supplementation is promising but yet inconclusive.

Has an aquatic diet been necessary for hominin brain evolution and functional development?

A number of authors have argued that only an aquatic-based diet can provide the necessary quantity of DHA to support the human brain, and that a switch to such a diet early in hominin evolution was critical to human brain evolution. This paper identifies the premises behind this hypothesis and critiques them on the basis of clinical literature. Both tissue levels and certain functions of the developing infant brain are sensitive to extreme variations in the supply of DHA in artificial feeding, and it can be shown that levels in human milk reflect maternal diet. However, both the maternal and infant bodies have mechanisms to store and buffer the supply of DHA, so that functional deficits are generally resolved without compensatory diets. There is no evidence that human diets based on terrestrial food chains with traditional nursing practices fail to provide adequate levels of DHA or other n-3 fatty acids. Consequently, the hypothesis that DHA has been a limiting resource in human brain evolution must be considered to be unsupported.

Fish oil and mental health: the role of n-3 long-chain polyunsaturated fatty acids in cognitive development and neurological disorders

Epidemiological and experimental studies have indicated that consumption of more n-3 long-chain polyunsaturated fatty acids may reduce the risk for a variety of diseases, including cardiovascular, neurological and immunological disorders, diabetes and cancer. This article focuses on the role of marine n-3 long-chain polyunsaturated fatty acids in brain functions, including the development of the central nervous system and neurological disorders. An overview of the major animal studies and clinical trials is provided here, focusing on fatty acid supplementation during pregnancy and infancy, and prevention and management of Alzheimer's disease, schizophrenia, depression and attention deficit hyperactive disorder. Although an optimal balance in n-3/n-6 long-chain polyunsaturated fatty acid ratio is important for proper neurodevelopment and cognitive functions, results from randomized controlled trials are controversial and do not confirm any useful effect of supplementation on development of preterm and term infants. The relationship between fatty acid status and mental disorders is confirmed by reduced levels of n-3 long-chain polyunsaturated fatty acids in erythrocyte membranes of patients with central nervous system disorders. Nevertheless, there are very little data supporting the use of fish oil in those patients. The only way to verify whether n-3 long-chain polyunsaturated fatty acids are a potential therapeutic option in the management and prevention of mental disorders is to conduct a large definitive randomized controlled trials similar to those required for the licensing of any new pharmacological treatment.

Impact of prenatal methylmercury exposure on neurobehavioral function at age 14 years

A cohort of 1022 consecutive singleton births was generated during 1987-1988 in the Faroe Islands, where increased methylmercury exposure occurs from traditional seafood diets that include pilot whale meat. The prenatal exposure level was determined from mercury analyses of cord blood, cord tissue, and maternal hair. At age 14 years, 878 of 1010 living cohort members underwent detailed neurobehavioral examination. Eighteen participants with neurological disorders were excluded. Blood and hair samples obtained from the participants were analyzed for mercury. The neuropsychological test battery was designed based on the same criteria as applied at the examination at age 7 years. Multiple regression analysis was carried out and included adjustment for confounders. Indicators of prenatal methylmercury exposure were significantly associated with deficits in finger tapping speed, reaction time on a continued performance task, and cued naming. Postnatal methylmercury exposure had no discernible effect. These findings are similar to those obtained at age 7 years, and the relative contribution of mercury exposure to the predictive power of the multiple regression models was also similar. An analysis of the test score difference between results at 7 and 14 years suggested that mercury-associated deficits had not changed between the two examinations. In structural equation model analyses, the neuropsychological tests were separated into five groups; methylmercury exposure was significantly associated with deficits in motor, attention, and verbal tests. These findings are supported by independent assessment of neurophysiological outcomes. The effects on brain function associated with prenatal methylmercury exposure therefore appear to be multi-focal and permanent.

Neurologic condition of healthy term infants at 18 months: positive association with venous umbilical DHA status and negative association with umbilical trans-fatty acids

Prenatal long-chain polyunsaturated fatty acids (LCPUFAs) and trans-fatty acids may affect neurodevelopment. In healthy term children, we determined relationships between relative fatty acid contents of umbilical arteries and veins and neurodevelopment at 18 mo. The study comprised a mixed group of 317 breast-fed, formula-fed, and LCPUFA formula-fed children. Study endpoints were the Hempel neurologic examination resulting in a neurologic classification and neurologic optimality score (NOS), and the Bayley Psychomotor Developmental Index (PDI) and Mental Developmental Index (MDI). Fifteen children showed minor neurologic dysfunction (MND). The umbilical vein trans, trans-18:2n-6 content was higher in children with MND than in the normal group. The NOS was significantly reduced in infants with an umbilical vein docosahexaenoic acid (DHA) content within the lowest quartile. Umbilical vein arachidonic acid (AA) was related to NOS in univariate statistics but not in multivariate analyses. The sum of trans-fatty acids and that of C18 trans-fatty acids showed a negative association with NOS in both univariate and multivariate analyses. No associations were found between AA, DHA and total trans-fatty acids with PDI or MDI. In conclusion, neonates with a relatively low DHA status and those with high trans-fatty acid levels have a less favorable neurologic condition at 18 mo.

Marine oil, and other prostaglandin precursor, supplementation for pregnancy uncomplicated by pre-eclampsia or intrauterine growth restriction

BACKGROUND

Population studies have shown that higher intakes of marine foods during pregnancy are associated with longer gestations, higher infant birthweights and a low incidence of pre-eclampsia. It is suggested that the fatty acids of marine foods may be the underlying cause of these associations.

OBJECTIVES

To estimate the effects of marine oil, and other prostaglandin precursor, supplementation during pregnancy on the risk of pre-eclampsia, preterm birth, low birthweight and small-for-gestational age.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (December 2005), The Cochrane Central Register of Controlled Trials (The Cochrane Library 2005, Issue 2) and MEDLINE (1966 to April 2005).

SELECTION CRITERIA

All randomised trials comparing oral marine oil, or other prostaglandin precursor, supplementation during pregnancy with either placebo or no treatment. Trials were excluded if their aim was to treat women with established pre-eclampsia or suspected intrauterine growth restriction.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, data extraction and trial quality.

MAIN RESULTS

Six trials, involving 2783 women, are included in this review. Three of these were rated as high quality, including the largest trial with 1477 women. Women allocated a marine oil supplement had a mean gestation that was 2.6 days longer than women allocated to placebo or no treatment (weighted mean difference (WMD), 2.55 days, 95% confidence interval (CI) 1.03 to 4.07 days; 3 trials, 1621 women). This was not reflected in a clear difference between the two groups in the relative risk (RR) of birth before 37 completed weeks, although women allocated marine oil did have a lower risk of giving birth before 34 completed weeks' gestation (RR 0.69, 95% CI 0.49 to 0.99; 2 trials, 860 women). Birthweight was slightly greater in infants born to women in the marine oil group compared with control (WMD 47 g, 95% CI 1 g to 93 g; 3 trials, 2440 women). However, there were no overall differences between the groups in the proportion of low birthweight or small-for-gestational age babies. There was no clear difference in the relative risk of pre-eclampsia between the two groups.

AUTHORS' CONCLUSIONS

There is not enough evidence to support the routine use of marine oil, or other prostaglandin precursor, supplements during pregnancy to reduce the risk of pre-eclampsia, preterm birth, low birthweight or small-for-gestational age.

Impact of prenatal methylmercury exposure on neurobehavioral function at age 14 years

A cohort of 1022 consecutive singleton births was generated during 1987-1988 in the Faroe Islands, where increased methylmercury exposure occurs from traditional seafood diets that include pilot whale meat. The prenatal exposure level was determined from mercury analyses of cord blood, cord tissue, and maternal hair. At age 14 years, 878 of 1010 living cohort members underwent detailed neurobehavioral examination. Eighteen participants with neurological disorders were excluded. Blood and hair samples obtained from the participants were analyzed for mercury. The neuropsychological test battery was designed based on the same criteria as applied at the examination at age 7 years. Multiple regression analysis was carried out and included adjustment for confounders. Indicators of prenatal methylmercury exposure were significantly associated with deficits in finger tapping speed, reaction time on a continued performance task, and cued naming. Postnatal methylmercury exposure had no discernible effect. These findings are similar to those obtained at age 7 years, and the relative contribution of mercury exposure to the predictive power of the multiple regression models was also similar. An analysis of the test score difference between results at 7 and 14 years suggested that mercury-associated deficits had not changed between the two examinations. In structural equation model analyses, the neuropsychological tests were separated into five groups; methylmercury exposure was significantly associated with deficits in motor, attention, and verbal tests. These findings are supported by independent assessment of neurophysiological outcomes. The effects on brain function associated with prenatal methylmercury exposure therefore appear to be multi-focal and permanent.

Relationship between umbilical cord essential fatty acid content and the quality of general movements of healthy term infants at 3 months

Prenatal essential fatty acid (EFA) status might be an important factor in the development of the central nervous system (CNS). The aim of the present study was to evaluate the relationship between the fatty acid compositions of the umbilical blood vessels at birth, used as a proxy of prenatal EFA status, and quality of general movements (GMs) at 3 mo. Umbilical artery and vein fatty acid compositions were investigated in a mixed group of breastfed infants and infants fed with formula with or without long-chain polyunsaturated fatty acid (LCPUFA) supplementation. At the age of 3 mo, video assessment of the quality of GMs was performed to evaluate neurologic condition. The quality of GMs was scored by assessing the degree of variation, complexity, and fluency. Outcomes were classified as normal-optimal, normal suboptimal, mildly abnormal, and definitely abnormal movements. Information on potential confounders, including the type of postnatal feeding, was collected prospectively. Associations between fatty acid status at birth and quality of GMs were investigated, and multinomial logistic regression analyses were carried out. None of the infants showed definitely abnormal movements. Infants with mildly abnormal GMs had a lower EFA index, lower arachidonic acid (AA) content, higher total n-9 fatty acid, and higher total monounsaturated fatty acid (MUFA) content in the umbilical artery compared with infants with normal GMs. Multivariate analyses confirmed these findings. We conclude that mildly abnormal GMs are associated with a less favorable EFA status in the umbilical artery.

Formula supplemented with docosahexaenoic acid (DHA) and arachidonic acid (ARA): a critical review of the research

PURPOSE

To summarize results of randomized controlled trials (RCTs) evaluating growth, cognitive, neurological, and visual development of term infants supplemented with docosahexaenoic acid (DHA) and arachidonic acid (ARA).

DESIGN AND METHODS

The Boyack and Lookinland Methodological Quality Index (MQI) was used to evaluate data from RCTs identified from multiple data bases.

RESULTS

Six of ten studies found the addition of DHA and ARA to have no significant effect on infant development.

PRACTICE IMPLICATIONS

More expensive formula with endogenous DHA and ARA is not necessary. Results from longer studies currently underway will be beneficial.

Serum lipid fatty acids and temporal processing acuity in children with oral clefts

We investigated the relation between a biological factor (fatty acids, FA) and a cognitive processing speed factor (temporal processing acuity, TPA) that are both suggested to relate to neuronal and cognitive functioning. Blood samples of 49 ten-year-old children with oral clefts were collected for FA analysis in serum triglycerides, cholesteryl esters, and phospholipids on the same day as they performed behavioral TPA tasks (simultaneity/nonsimultaneity judgments) in several perceptual modalities (visual, auditory, tactile, audiotactile, visuotactile, and audiovisual). This population has larger than expected variation in the relevant cognitive measures (TPA, learning ability, and intelligence). Sequential regression analyses (adjusted for age, gender, and cleft type) showed that saturated FAs were not generally associated with TPA. Monounsaturated erucic and nervonic acids were inversely related with TPA. Of the polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids were positively associated with TPA, whereas gamma-linolenic acid was inversely related to TPA. In summary, we found significant relations between a biological (certain FAs) and a cognitive factor (TPA).

Cognitive and physiological effects of Omega-3 polyunsaturated fatty acid supplementation in healthy subjects

BACKGROUND

It has been reported that Omega-3 fatty acids may play a role in nervous system activity and that they improve cognitive development and reference memory-related learning, increase neuroplasticity of nerve membranes, contribute to synaptogenesis and are involved in synaptic transmission. The aim of this study was to examine the effects of Omega-3 supplementation on some cognitive and physiological parameters in healthy subjects.

MATERIALS AND METHODS

Subjects were tested at the beginning of the experiment and after 35 days. In this period they were supplemented with Omega-3 polyunsaturated fatty acids. A group was supplemented with olive oil (placebo). Tests involving different types of attention were used, i.e. Alert, Go/No-Go, Choice and Sustained Attention. For each test, the reaction time, the event-related potentials by electroencephalogram (EEG) and the electromyography (EMG) of the forefinger flexor muscle were recorded. The Profile of Mood States test (POMS) was also administered.

RESULTS

Blood analyses showed that after Omega-3 supplementation the arachidonic acid/eicosapentaenoic acid ratio (AA/EPA) was strongly reduced. The mood profile was improved after Omega-3 with increased vigour and reduced anger, anxiety and depression states. This was associated with an effect on reactivity with a reduction of reaction time in the Go/No-Go and Sustained Attention tests. The latency of EMG activation was concomitantly reduced in the same tests plus Choice. An EEG frequency shift towards the theta and alpha band were recorded in all the tests after Omega-3.

CONCLUSIONS

Omega-3 supplementation is associated with an improvement of attentional and physiological functions, particularly those involving complex cortical processing. These findings are discussed in terms of the influence of Omega-3 on the central nervous system.

Association Between School Performance, Breast Milk Intake and Fatty Acid Profile of Serum Lipids in Ten-Year-Old Cleft Children

The fatty acid profiles of serum lipids were examined in 53 ten-year-old cleft children. The children presented with different cleft types (cleft lip, cleft lip and palate, isolated cleft palate and submucuous cleft palate) and were recruited from the Finnish Cleft Center. We also studied associations between serum lipid fatty acids and early breast milk intake, cognitive development in terms of preschool language learning and school achievement. The fatty acid profiles of serum lipids did not differ between boys and girls. The proportion of myristic acid in serum cholesteryl esters (CE) was higher and proportion of nervonic acid in phospholipids (PL) lower in children with isolated palatal clefts than in those with submucuous clefts. Out of the present children, 30% and 60% received breast milk less than 1 or 3 months, respectively. The proportions of docosahexaenoic acid in CE and in PL were significantly higher in the children whose breast milk intake was longer than 3 months. The number of children requiring special education was higher among those who received breast milk less than 1 month than among those with longer breast milk intake. In conclusion, the fatty acid profiles of serum lipids seem to be comparable among children with different cleft types. Short breast milk intake was associated with poorer school performance.

Essential fatty acid transfer and fetal development

Docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) are important structural components of the central nervous system. These fatty acids are transferred across the placenta, and are accumulated in the brain and other organs during fetal development. Depletion of 22:6n-3 from the retina and brain results in reduced visual function and learning deficits: these may involve critical roles of 22:6n-3 in membrane-dependent signaling pathways and neurotransmitter metabolism. Transfer of 22:6n-3 across the placenta involves specific binding and transfer proteins that facilitate higher concentrations of 22:6n-3 and 20:4n-6, but lower linoleic acid (18:2n-6) in fetal compared with maternal plasma, or in the breast-fed or formula-fed infant. However, human and animal studies both demonstrate that maternal diet impacts fetal 22:6n-3 and 20:4n-6 accretion. After birth, parenteral lipid, human milk and infant formula feeding all result in a marked decrease in plasma 22:6n-3 and 20:4n-6 and an increase in 18:2n-6. Estimation of fetal tissue fatty acid accretion suggests that current preterm infant feeds are unlikely to meet in utero rates of 22:6n-3 accretion. Consideration needs to be given to whether fetal plasma 22:6n-3 and 20:4n-6 enrichment and the low 18:2n-6 facilitates accretion of 22:6n-3 and 20:4n-6 in developing tissues.

Is docosahexaenoic acid, an n-3 long-chain polyunsaturated fatty acid, required for development of normal brain function? An overview of evidence from cognitive and behavioral tests in humans and animals

This review is part of a series intended for nonspecialists that will summarize evidence relevant to the question of whether causal relations exist between micronutrient deficiencies and brain function. Here, we focus on experiments that used cognitive or behavioral tests as outcome measures in experimental designs that were known to or were likely to result in altered brain concentrations of the n-3 fatty acid docosahexaenoic acid (DHA) during the perinatal period of "brain growth spurt." Experimental designs reviewed include observational breastfeeding studies and randomized controlled trials in humans and studies in rodents and nonhuman primates. This review is based on a large number of expert reviews and commentaries and on some 50 recent studies in humans and animals that have not yet been included in published reviews. Expert opinion regarding the strengths and weaknesses of the major experimental systems and uncertainties associated with interpreting results is summarized. On the basis of our reading of this literature, we conclude that evidence from several types of studies, particularly studies in animals, suggests that, within the context of specific experimental designs, changes in brain concentrations of DHA are positively associated with changes in cognitive or behavioral performance. Additional experimental information required to conclude that a causal association exists is discussed, as are uncertainties associated with applying results from specific experimental designs to the question of whether infant formula should be supplemented with DHA.

Lower fetal status of docosahexaenoic acid, arachidonic acid and essential fatty acids is associated with less favorable neonatal neurological condition

Long-chain polyunsaturated fatty acids, notably arachidonic (AA) and docosahexaenoic (DHA) acids are abundant in brain and may be conditionally essential in fetal life. We investigated umbilical artery (UA) and vein (UV) fatty acid compositions and early neonatal neurological condition in 317 term infants. Neurological condition was summarized as a clinical classification and a 'neurological optimality score' (NOS). Neurologically abnormal infants (n=27) had lower UV DHA and essential fatty acid (EFA) status. NOS correlated positively with AA (UV), and EFA (UV) and DHA status (UV and UA) and negatively with 18:2omega6 and omega9 (UV), and 20:3omega9, omega7 and C18 trans fatty acids (UV and UA). UV DHA, AA, saturated fatty acids, gestational age and obstetrical optimality score explained 16.2% of the NOS variance. Early postnatal neurological condition seems negatively influenced by lower fetal DHA, AA and EFA status. C18 trans fatty acids and 18:2omega6 may exert negative effects by impairment of LCP status.

Nutrients, neurodevelopment, and mood

Human neurodevelopment is the result of genetic and environmental interactions. This paper examines the role of prenatal nutrition relative to psychiatric disorders and explores the relationship among nutrients, mood changes, and mood disorders. Epidemiologic studies have found that adults who were born with a normal, yet low birth weight have an increased susceptibility to diseases such as coronary heart disease, diabetes, and stroke in adulthood. Prenatal caloric malnutrition, low birth weight, and prematurity also increase the risk for neurodevelopmental disorders, schizophrenia, affective disorders, and schizoid and antisocial personality disorders. Placebo-controlled studies in medicated patients suggest that add-on treatment with omega-3 fatty acids, particularly eicosapentaenoic acid, may ameliorate symptoms of major depressive disorder. Additional studies are necessary to confirm any benefits for bipolar disorders.

The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence

The UK dietary guidelines for cardiovascular disease acknowledge the importance of long-chain omega-3 polyunsaturated fatty acids (PUFA) - a component of fish oils - in reducing heart disease risk. At the time, it was recommended that the average n-3 PUFA intake should be increased from 0.1 to 0.2 g day(-1). However, since the publication of these guidelines, a plethora of evidence relating to the beneficial effects of n-3 PUFAs, in areas other than heart disease, has emerged. The majority of intervention studies, which found associations between various conditions and the intake of fish oils or their derivatives, used n-3 intakes well above the 0.2 g day(-1) recommended by Committee on Medical Aspects of Food Policy (COMA). Furthermore, in 2004, the Food Standards Agency changed its advice on oil-rich fish creating a discrepancy between the levels of n-3 PUFA implied by the new advice and the 1994 COMA guideline. This review will examine published evidence from observational and intervention studies relating to the health effects of n-3 PUFAs, and discuss whether the current UK recommendation for long-chain n-3 PUFA needs to be revisited.

The Tohoku Study of Child Development: A Cohort Study of Effects of Perinatal Exposures to Methylmercury and Environmentally Persistent Organic Pollutants on Neurobehavioral Development in Japanese Children

Several birth cohort studies have shown adverse effects of perinatal exposures to methylmercury (MeHg) and environmentally persistent organic pollutants (POPs). These chemicals are ingested mainly through fish consumption, but little is known about the hazardous effects in Japanese, whose fish consumption is high. The present study, the Tohoku Study of Child Development, was designed to examine the effects of perinatal exposures to MeHg, polychlorinated biphenyls (PCB), dioxins, pesticides, and other chemicals in Japanese children. Six hundred eighty-seven pregnant women were participated in this study with their written informed consent. Maternal peripheral blood, cord blood, cord tissue, placenta, and breast milk samples were collected for chemical analysis. Maternal hair was also taken for MeHg analysis. Infants born at full term were assessed by neurobehavioral tests: the Brazelton Neonatal Behavioral Assessment Scale at three days old, the Kyoto Scale of Psychological Development and the Bayley Scales of Infant Development at 7 and 18 months old, and the Fagan Test of Infant Intelligence at 7 months old. The children will be continuously followed up to ages 6-7 years. Maternal food intake frequency, maternal IQ, socioeconomic status, and home environment were assessed as covariates. The results of this cohort study will allow us to evaluate associations between the neurobehavioral development of children and perinatal exposures to MeHg and environmentally POPs in Japan.