Gestational age and birth weight in relation to n-3 fatty acids among Inuit (Canada)

Persistent, bioaccumulative and toxic substances in fish: human health considerations

Fish are important dietary items that provide essential nutrients. Fish however, bioaccumulate monomethyl mercury (MMHg) and organo-halogenated pollutants (OHP) that are persistent bioaccumulative and toxic substances (PBTS). Unlike man-made OHP, MMHg is mainly of natural origin but background concentrations of aquatic systems are determined by the environmental Hg-methylating potential. Industrial activities can modulate environmental discharges and fish bioaccumulation of PBTS. Fish and seafood consumption are associated with human body load of PBTS, but farming practices that utilize fishmeal increase the terrestrial food chain resulting in farm-animal accumulation of PBTS. These substances are neurotoxic and endocrine active that can impact humans and wild life, but chemical characteristics of MMHg and OHP modulate interactions with animal tissues. MMHg is protein reactive with a faster metabolism (months) than OHP that are stored and slowly (years) metabolized in fat tissues. Except for brain-Hg, neither Hg nor OHP in tissues are markers of toxic effects; however, deficits in neurobehavioral test-scores of children have been shown in some fish-eating populations. These deficits are transient and within normal range, and are not prodromes of neurological diseases. Although population studies show that consumption of fish at current levels of contamination do not explain neurological disorders, endocrine activity remains controversial. Understanding risk of hazard caused by fish-PBTS consumption requires a wide range of expertise. We discuss chemical, toxic, metabolic, and ecological characteristics associated with PBTS in fish. There are proven health outcome derived from fish consumption, while risk of exposure to avoidable PBTS is a chance that can be minimized by societal actions.

Maternal n-3, n-6, and trans fatty acid profile early in pregnancy and term birth weight: a prospective cohort study

BACKGROUND

Maternal n-3, n-6, and trans fatty acids are claimed to affect fetal growth, yet evidence is limited.

OBJECTIVE

We investigated the association between maternal n-3, n-6, and trans fatty acids measured early in pregnancy and fetal growth.

DESIGN

Amsterdam pregnant women (n = 12 373) were invited to complete a questionnaire (response 67%) and donate blood around the 12th pregnancy week for nutrient analysis. For 4336 women, fatty acid concentrations were measured in plasma phospholipids (gas-liquid chromatography). Associations of these concentrations with birth weight and small-for-gestational-age (SGA) risk were analyzed (liveborn singleton term deliveries, n = 3704).

RESULTS

Low concentrations of individual n-3 fatty acids and 20:3n-6, the precursor of arachidonic acid (20:4n-6), but high concentrations of the other n-6 fatty acids and the main dietary trans fatty acid (18:1n-9t) were associated with lower birth weight (estimated difference in univariate analysis -52 to -172 g for extreme quintile compared with middle quintile). In general, SGA risk increased accordingly. After adjustment for physiologic, lifestyle-related and sociodemographic factors, low concentrations of most n-3 fatty acids and 20:3n-6 and high concentrations of 20:4n-6 remained associated with lower birth weight (-52 to -57 g), higher SGA risk, or both (odds ratios: 1.38-1.50). Infants of the 7% of women with the most adverse fatty acid profile were on average 125 g lighter and twice as likely to be small for gestational age.

CONCLUSION

An adverse maternal fatty acid profile early in pregnancy is associated with reduced fetal growth, which, if confirmed, gives perspective for the dietary prevention of lower birth weight.

Beneficial effects of a polyunsaturated fatty acid on infant development: evidence from the inuit of arctic Quebec

OBJECTIVES

To examine the relation of cord plasma docosahexaenoic acid (DHA) concentration to gestation length, birth size, growth, and infant visual acuity, cognitive, and motor development and the effects on growth and development associated with DHA intake from breast-feeding.

STUDY DESIGN

DHA, other polyunsaturated fatty acids, and 3 environmental contaminants (polychlorinated biphenyls, mercury, and lead) were assessed in cord plasma and maternal plasma and milk in 109 Inuit infants in Arctic Quebec. Multiple regression was used to examine the relation of cord DHA and DHA from breast-feeding on growth and development at 6 and 11 months, after controlling for contaminant exposure and other potential confounders.

RESULTS

Higher cord DHA concentration was associated with longer gestation, better visual acuity and novelty preference on the Fagan Test at 6 months, and better Bayley Scale mental and psychomotor performance at 11 months. By contrast, DHA from breast-feeding was not related to any indicator of cognitive or motor development in this full-term sample.

CONCLUSIONS

The association of higher cord DHA concentration with more optimal visual, cognitive, and motor development is consistent with the need for substantial increases in this critically important fatty acid during the third trimester spurt of synaptogenesis in brain and photoreceptor development.

Assessment of intrauterine methylmercury exposure affecting child development: messages from the newborn

In evaluating the health effects in the offspring born to the mothers exposed to methylmercury (MeHg) during pregnancy, biomarkers obtained from maternal blood and hair, and umbilical cord have been employed for the exposure assessment. However, which biomarker is employed may affect the study conclusion. In this sense, umbilical cord mercury concentration appears to be a direct exposure biomarker of the fetus. We present an overview of the studies addressing umbilical cord and mercury and scrutinize the usefulness of umbilical cord samples for intrauterine exposure assessment of MeHg. The mean total mercury concentration in cord blood ranged from 0.5 to 35.6 microg/L among the studies reviewed. In Japanese populations, MeHg concentrations in dry cord tissue did not exceed 0.4 microg/g. Also, dry cord tissue would be preferable to wet tissue because the definition of wet weight of the umbilical cord is ambiguous. The cord blood-to-maternal blood ratio of mercury concentrations differed considerably among mother-child pairs despite the significant positive correlation between the cord and maternal mercury concentrations. Moreover, the increased cord mercury concentration was associated with some neurobehavioral and neurophysiological deficits in child. Therefore, mercury concentrations in cord blood and tissue can be accepted as more useful and valid biomarkers of fetal exposure to MeHg, for assessing a dose-response relationship in children at the developmental stage, than maternal mercury concentrations at parturition. Because umbilical cord blood has been used for cord-blood stem cell transplants, dry umbilical cord tissue should be effectively utilized for the advancement of medical sciences.

[Usefulness of umbilical cord mercury concentrations as biomarkers of fetal exposure to methylmercury]

In epidemiological studies on the health effect of methylmercury (MeHg) exposure, maternal-hair mercury concentration has been used as an exposure biomarker because of its ease of collection and capability to recapture the exposure history. However, artificial hair-waving reduces the mercury concentration and there is little agreement about which part of the hair strand properly represents fetal exposure. We presented an overview of the studies addressing umbilical cord and mercury in PubMed and evaluated the usefulness of umbilical cord mercury concentrations as biomarkers of fetal exposure to MeHg. The mean total mercury (T-Hg) concentration in cord blood was between 0.5 and 35.6microg/l, and the cord blood-to-maternal blood ratio of T-Hg concentrations was estimated to be approximately 1.5. MeHg concentrations in dried cord tissue did not exceed 0.4 microg/g in Japanese populations without particular exposure to MeHg. Dried cord tissue appeared to be better than wet tissue because the definition of wet weight of the umbilical cord is ambiguous. Both cord-blood and cord-tissue mercury concentrations seemed to correlate closely with maternal-hair and maternal-blood ones. Since cord mercury concentrations are a direct exposure biomarker of the fetus and the cord blood-to-maternal blood ratio of mercury differed markedly among mother-child pairs, mercury concentration in cord blood or dried cord tissue should therefore be used in assessing the possible effects of fetal exposure to MeHg on the susceptible brain. Further studies are required to clarify at which period of exposure during gestation the cord mercury concentration represents in relation to mercury concentrations in maternal segmental hair.

Maternal fish consumption, mercury levels, and risk of preterm delivery

BACKGROUND

Pregnant women receive mixed messages about fish consumption in pregnancy because unsaturated fatty acids and protein in fish are thought to be beneficial, but contaminants such as methylmercury may pose a hazard.

METHODS

In the Pregnancy Outcomes and Community Health (POUCH) study, women were enrolled in the 15th to 27th week of pregnancy from 52 prenatal clinics in five Michigan communities. At enrollment, information was gathered on amount and category of fish consumed during the current pregnancy, and a hair sample was obtained. A segment of hair closest to the scalp, approximating exposure during pregnancy, was assessed for total mercury levels (70-90% methylmercury) in 1,024 POUCH cohort women.

RESULTS

Mercury levels ranged from 0.01 to 2.50 pg/g (mean = 0.29 microg/g; median = 0.23 microg/g). Total fish consumption and consumption of canned fish, bought fish, and sport-caught fish were positively associated with mercury levels in hair. The greatest fish source for mercury exposure appeared to be canned fish. Compared with women delivering at term, women who delivered before 35 weeks' gestation were more likely to have hair mercury levels at or above the 90th percentile (> or = 0.55 microg/g), even after adjusting for maternal characteristics and fish consumption (adjusted odds ratio = 3.0; 95% confidence interval, 1.3-6.7).

CONCLUSION

This is the first large, community-based study to examine risk of very preterm birth in relation to mercury levels among women with low to moderate exposure. Additional studies are needed to see whether these findings will be replicated in other settings.