Maternal Exposure to Cadmium and Fetal Growth: a Systematic Review and Meta-Analysis

Review: Strategies for limiting dietary cadmium in cereals

Cadmium (Cd) is a toxic metal, which in some production areas reaches levels above allowed limits in cereals. Thus, reducing its concentration in cereals is crucial for mitigating health risks and complying with food safety regulations. This review evaluates strategies to reduce Cd accumulation in cereal grains by mitigating soil Cd contamination and its bioavailability to plants. It covers methods for Cd estimation in soil and explores biological, chemical, and genetic approaches to limit Cd uptake by crops. The effectiveness of these strategies depends on genetic factors, soil properties, and crop type. Key approaches include traditional breeding, genome editing, digital and predictive soil mapping, and silicon (Si) and selenium (Se) supplementation. Traditional breeding, enhanced by modern genetic tools, enables the development of high-yielding, low-Cd cultivars but is time-consuming. Genome editing, particularly CRISPR-Cas9, offers precise gene modifications to reduce Cd uptake but faces regulatory constraints. Digital and predictive soil mapping provide high-resolution maps for targeted interventions but require extensive calibration. Silicon supplementation is a promising approach, as it competes with Cd for uptake sites, and limits Cd translocation to edible plant parts. Additionally, Si enhances plant tolerance to abiotic stresses, making it a multifunctional solution. Selenium supplementation can also reduce Cd accumulation while offering health benefits. However, the effectiveness of both Si and Se vary with dosage and crop type. An integrated approach combining these strategies is essential for effective Cd reduction in cereals. Continued research, technological advancements, and supportive policies are crucial for ensuring safe and sustainable cereal production.

Cadmium exposure and health outcomes:An umbrella review of meta-analyses

OBJECTIVE

This umbrella review synthesizes evidence from meta-analyses to assess the health outcomes associated with cadmium (Cd) exposure.

METHODS

Literature search was conducted in four Databases: PubMed, Embase, APA PsycNe, and the Cochrane Databases. Evaluating evidence strength via Assess Systematic Reviews 2 (AMSTAR 2), umbrella review methodology and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE).

RESULTS

Our review encompassed 79 non-overlapping studies, investigating 48 unique health outcomes through 113 independent effect sizes. Using the AMSTAR 2 tool, we found that 2 (3 %) meta-analyses were rated as high quality, 6 (8 %) as moderate quality, 38 as low quality, and 33 as very low quality. Applying the GRADE criteria, we observed that 1 (1 %) effect size was rated A (male fertility), 8 (7 %) were rated B (breast cancer, prostate cancer, hypertension, stroke, urolithiasis), 30 were rated C, and 74 were rated D. According to the umbrella review methodology, 5 (4 %) outcomes provided highly suggestive evidence, 13 (12 %) provided suggestive evidence, 51 provided weak evidence (class IV), and 44 had insufficient evidence for statistically significant results (class V). Meta-analyses on circulatory diseases, pregnancy outcomes, perinatal outcomes, skeletal and connective tissue diseases, neurological disorders, urinary system diseases, and male fertility had >80 % statistically significant results, while endocrine system diseases and mental and behavioral disorders had <33 %.

CONCLUSION

Cd exposure is significantly linked to various health outcomes, with implications for clinical practice and public health recommendations.

Sex-specific associations between maternal exposure to metal mixtures and fetal growth trajectories: A prospective birth cohort study

BACKGROUND

The associations of prenatal metals exposure with birth outcomes have been widely assessed. However, evidence on the associations between metal mixtures and fetal intrauterine growth trajectories is scarce.

OBJECTIVES

This study aimed to explore the associations of metal mixtures with fetal intrauterine growth trajectories overall and by sex.

METHODS

We analyzed data from the Ma'anshan birth cohort, which included a total of 1041 pregnant woman. The concentrations of 12 metals in maternal blood were measured during early pregnancy, and fetal intrauterine growth indicators were standardized and assessed at 16, 23, 30, 34, and 38 weeks of gestation. We used generalized linear regression and linear mixed models to identify the key fetal growth indicator (biparietal diameter (BPD)), and applied GBTM to characterize BPD SD-scores trajectories. To further assess the individual and combined effects of metals, we conducted multivariable logistic regression and repeated holdouts weighted quantile sum (WQS) regression analyses, respectively. Finally, we performed a sex-stratified analysis to explore sex-specific associations.

RESULTS

The sex-stratified multivariable logistic regression analysis indicated that in male fetal, cobalt (Co) (OR: 0.60, 95 % CI: 0.38, 0.92) was negatively associated with the high-growth BPD-SD scores trajectory. In contrast, Co (OR: 2.39, 95 % CI: 1.40, 4.45) showed a positive association in female fetal. Results from the WQS showed that early pregnancy metal mixture exposure was associated with BPD-SD scores at 16, 34, and 38 weeks in female fetal. The results highlighted Zn and Co as key metals associated with high-growth BPD SD-scores trajectory. We also identified a significant interaction between early pregnancy metal mixtures and sex on high-growth BPD SD-scores trajectories. The WQS*sex interaction term had a mean odds ratio of 1.271 (95 % CI: 1.027, 1.619).

CONCLUSION

This study suggests that exposure to prenatal metal mixtures affects fetal intrauterine growth trajectories with sexual dimorphism.

Associations of prenatal one-carbon metabolism nutrients and metals with epigenetic aging biomarkers at birth and in childhood in a US cohort

Epigenetic gestational age acceleration (EGAA) at birth and epigenetic age acceleration (EAA) in childhood may be biomarkers of the intrauterine environment. We investigated the extent to which first-trimester folate, B12, 5 essential, and 7 non-essential metals in maternal circulation are associated with EGAA and EAA in early life. Bohlin EGAA and Horvath pan-tissue and skin and blood EAA were calculated using DNA methylation measured in cord blood (N=351) and mid-childhood blood (N=326; median age = 7.7 years) in the Project Viva pre-birth cohort. A one standard deviation increase in individual essential metals (copper, manganese, and zinc) was associated with 0.94-1.2 weeks lower Horvath EAA at birth, and patterns of exposures identified by exploratory factor analysis suggested that a common source of essential metals was associated with Horvath EAA. We also observed evidence nonlinear associations of zinc with Bohlin EGAA, magnesium and lead with Horvath EAA, and cesium with skin and blood EAA at birth. Overall, associations at birth did not persist in mid-childhood; however, arsenic was associated with greater EAA at birth and in childhood. Prenatal metals, including essential metals and arsenic, are associated with epigenetic aging in early life, which might be associated with future health.

Exposure to heavy metals and trace elements among pregnant women with twins: levels and association with twin growth discordance

Background

Twin growth discordance is one of the leading causes of perinatal mortality in twin pregnancies. Whether prenatal exposure to heavy metals and trace elements is associated with twin growth discordance has not been studied yet.

Objective

To evaluate the prenatal level of heavy metals and trace elements in twin pregnancy and its relationship with twin growth discordance.

Methods

This study involving 60 twin pairs and their mothers was conducted in Zhejiang Province, China, in 2020-2021. The concentration of heavy metals and trace elements in maternal blood, umbilical cord, and placenta were collected at delivery and measured by inductively coupled plasma tandem mass spectrometer. The association of prenatal level with twin growth discordance was evaluated using conditional logistic regression.

Results

High levels of heavy metal elements (thallium in maternal blood and umbilical cord blood of larger twins, vanadium in the placenta of larger twins) and trace elements (iodine in the placenta of larger twins) during pregnancy, as well as low levels of heavy metal elements (strontium in the umbilical cord blood of larger twins, strontium and chromium in the umbilical cord blood of smaller twins, strontium in the placenta of larger twins, molybdenum and lead in the placenta of smaller twins and difference of molybdenum in the placenta of twins), are associated with intertwin birthweight discordance. Univariate regression analyses showed a significant effect of gestational age at delivery and eleven trace element data on intertwin birthweight discordance. Multivariable logistic regression analysis with transformed variables as dichotomous risk factors combined with baseline demographic characteristics showed Tl in maternal blood as an independent risk factor. The model constructed by combining Tl in maternal blood (OR = 54.833, 95% CI, 3.839-83.156) with the gestational week (OR = 0.618, 95% CI, 0.463-0.824) had good predictive power for intertwin birthweight discordance (AUC = 0.871). The sensitivity analysis results indicate that the effect of maternal blood thallium on intertwin birthweight discordance is stable and reliable.

Conclusion

To our knowledge, ours is the first case-control study to investigate the association between elevated maternal thallium levels before delivery and twin growth discordance.

Exposure to metal mixtures and adverse pregnancy and birth outcomes: A systematic review

BACKGROUND

Prenatal exposure to metal mixtures is associated with adverse pregnancy and birth outcomes like low birth weight, preterm birth, and small for gestational age. However, prior studies have used individual metal analysis, lacking real-life exposure scenarios.

OBJECTIVES

This systematic review aims to evaluate the strength and consistency of the association between metal mixtures and pregnancy and birth outcomes, identify research gaps, and inform future studies and policies in this area.

METHODS

The review adhered to the updated Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) checklist, along with the guidelines for conducting systematic reviews and meta-analyses of observational studies of etiology (COSMOS-E). Our data collection involved searching the PubMed, MEDLINE, and SCOPUS databases. We utilized inclusion criteria to identify relevant studies. These chosen studies underwent thorough screening and data extraction procedures. Methodological quality evaluations were conducted using the NOS framework for cohort and case-control studies, and the AXIS tool for cross-sectional studies.

RESULTS

The review included 34 epidemiological studies, half of which focused on birth weight, and the others investigated neonate size, preterm birth, small for gestational age, miscarriage, and placental characteristics. The findings revealed significant associations between metal mixtures (including mercury (Hg), nickel (Ni), arsenic (As), cadmium (Cd), manganese (Mn), cobalt (Co), lead (Pb), zinc (Zn), barium (Ba), cesium (Cs), copper (Cu), selenium (Se), and chromium (Cr)) and adverse pregnancy and birth outcomes, demonstrating diverse effects and potential interactions.

CONCLUSION

In conclusion, this review consistently establishes connections between metal exposure during pregnancy and adverse consequences for birth weight, gestational age, and other vital birth-related metrics. This review further demonstrates the need to apply mixture methods with caution but also shows that they can be superior to traditional approaches. Further research is warranted to deeper understand the underlying mechanisms and to develop effective strategies for mitigating the potential risks associated with metal mixture exposure during pregnancy.

Cadmium reduces growth of male fetuses by impairing development of the placental vasculature and reducing expression of nutrient transporters

In utero exposure to the toxic metal cadmium (Cd) alters fetoplacental growth in rodents and has been inversely associated with birth weight and infant size in some birth cohorts. Moreover, studies suggest that Cd may have differential effects on growth and development according to offspring sex. The purpose of the current study was to evaluate changes in male and female fetoplacental development following a single injection of saline (5 ml/kg ip) or cadmium chloride (CdCl2, 2.5, 5 mg/kg, ip) on gestational day (GD) 9. By GD18, no changes in fetal or placental weights were observed after treatment with 2.5 mg/kg CdCl2. By comparison, the weight and length of male fetuses and their placentas were reduced following treatment with 5 mg/kg CdCl2 whereas no change was observed in females. In addition, the area of maternal and fetal blood vessels as well as the expression of the glucose transporters, Glut1 and Glut3, and the endothelial marker, CD34, were reduced in the placentas of CdCl2-treated male offspring compared to females. Interestingly, the placentas of females accumulated 80% more Cd than males after CdCl2 (5 mg/kg) administration. Female placentas also had higher concentrations of zinc and the zinc transporter Znt1 compared to males which may explain the limited changes in fetal growth observed following CdCl2 treatment. Taken together, disruption of vasculature development and reduced expression of glucose transporters in the placenta provide potential mechanisms underlying reduced fetal growth in male offspring despite the greater accumulation of Cd in female placentas.

Content of selected heavy metals in the umbilical cord blood and anthropometric data of mothers and newborns in Poland: preliminary data

The ability to accumulate metals in organs and tissues leads to disturbances in the physiological functioning of the body, causing oxidative stress. This negatively affects the functioning of the placenta and may result in miscarriages, premature birth and fetal growth disorders. The aim of the study was to examine the relationship between the levels of selected heavy metals in umbilical cord blood and anthropometric parameters of mothers and the newborns. Content of elements in umbilical cord blood has been assessed by high-resolution inductively coupled plasma optical emission spectroscopy (ICP-OES). The study results were collected and statistically analyzed using IBM SPSS Statistics software (PS IMAGO). The Pearson correlation coefficient was used to test for associations between selected variables. Regression analysis was conducted to identify predictors of anthropometric parameters of studied women and newborns. The study group consisted of women aged 19-41, whose pregnancy was uncomplicated and were not exposed to heavy metals due to their work or smoking. The following metals were identified in all collected cord blood samples: lead (26.25 ± 9.32 µg/L), zinc (2025.24 ± 717.83 µg/L), copper (749.85 ± 203.86 µg/L), manganese (32.55 ± 13.58 µg/L), chromium (8.34 ± 2.16 µg/L) and selenium (158.46 ± 41.58 µg/L). The conducted statistical analysis indicated the relationship between the copper content in the umbilical cord blood and the weight gain of pregnant women. A significant relationship was observed between newborn head circumference and chromium content. In addition, significant positive correlations were found between the content of zinc and copper, manganese and lead, manganese and selenium, lead and selenium, and lead and chromium in umbilical cord blood. The ratio of zinc to copper concentrations was related to neonatal head circumference. Weight gain in pregnant women is positively correlated with the copper level in umbilical cord blood. There is an association between head circumference at birth and the chromium concentration in umbilical cord blood. Copper and zinc levels in umbilical cord blood are positively correlated with head circumference at birth.

Effects of Non-Essential "Toxic" Trace Elements on Pregnancy Outcomes: A Narrative Overview of Recent Literature Syntheses

Adverse pregnancy outcomes and their complications cause increased maternal and neonatal morbidity and mortality and contribute considerably to the global burden of disease. In the last two decades, numerous narrative and systematic reviews have emerged assessing non-essential, potentially harmful, trace element exposure as a potential risk factor. This narrative review summarizes the recent literature covering associations between exposure to cadmium, lead, arsenic, and mercury and pregnancy outcomes and highlights common limitations of existing evidence that may hinder decision-making within public health. Several initial scoping searches informed our review, and we searched PubMed (latest date July 2022) for the literature published within the last five years reporting on cadmium, lead, arsenic, or mercury and pre-eclampsia, preterm birth, or prenatal growth. Pre-eclampsia may be associated with cadmium and strongly associated with lead exposure, and exposure to these metals may increase risk of preterm birth. Many reviews have observed cadmium to be negatively associated with birth weight. Additionally, lead and arsenic exposure may be negatively associated with birth weight, with arsenic exposure also adversely affecting birth length and head circumference. These findings should be interpreted with caution due to the limitations of the reviews summarized in this paper, including high heterogeneity due to different exposure assessment methods, study designs, and timing of sampling. Other common limitations were the low quality of the included studies, differences in confounding variables, the low number of studies, and small sample sizes.

Maternal exposure to heavy metals and risk for severe congenital heart defects in offspring

BACKGROUND

Congenital heart defects (CHDs) are the most common congenital malformations with a complex etiology, and environmental factors play an important role. Large epidemiology studies on prenatal exposure to selected heavy metals and their association with risk for CHDs are scarce and joint effects are not well understood.

OBJECTIVES

To examine the association between prenatal exposure to selected heavy metals and risk for CHDs.

METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the maternal plasma concentrations of arsenic, cadmium, mercury, lead, and manganese were in 303 CHD cases and 303 healthy controls that were recruited in eight hospitals in China. Generalized linear mixed model (GLMM) and Bayesian kernel machine regression (BKMR) were fitted to evaluate the individual and joint effects of metal concentrations on CHDs.

RESULTS

In GLMM, two metals were each significantly associated with an increased risk for CHDs [adjusted odds ratio (95% confidence interval): mercury, 2.88 (1.22-6.77); lead, 2.74 (1.00-7.57)]. In BKMR, CHD risk increased with mixture levels of the five metals when their concentrations were at the 40th percentile or higher, compared to when all metals were below their 35th percentile, and mercury was the major metal that contributed to the mixture effect. The interaction between mercury and lead was observed in BKMR.

CONCLUSIONS

Using metal concentrations in maternal plasma obtained during the second or third trimester as exposure markers, we found that the risk of CHDs increased with the levels of the mixtures of As, Cd, Hg, Pb, and Mn, with Hg being the most important contributor to the mixture effect.

The Association Between Heavy Metals Exposure and Sex Hormones: a Systematic Review on Current Evidence

The general population is voluntarily or unintentionally exposed to heavy metals through ingestion of food, polluted water, or contact with soil, dust, or polluted air. A number of metals are considered as endocrine disruptors and can alter the level of reproductive hormones. This study aims to systematically review the epidemiological studies on the association between heavy metals exposure and sex hormones level. We conducted a systematic search from available databases, including PubMed, Clarivate Web of Science, Scopus, Google Scholar, and Cochrane Collaboration, until April 2021. The relevant studies were selected, and two reviewers conducted the quality assessment. Then, data were extracted based on the inclusion criteria. We identified nine articles related to the association between heavy metals exposure and sex hormones level. We summarized the relevant information. Due to the diversity of metals and the variety of sex hormones, the effect of exposure on hormones level was not clear; however in most studies, at least for one metal, a significant association (inverse or positive) was observed between metals exposure and hormones level. Heavy metals exposure may potentially alter sex hormone levels; however, further research is needed to evaluate the impact of this association.

Relationship between maternal heavy metal exposure and congenital heart defects: a systematic review and meta-analysis

Congenital heart defects (CHDs) are one of the major causes of death in infants and young children, and heavy metal exposure during pregnancy is one of the possible risk factors. However, the effect of heavy metal exposure on CHDs is still controversial. We searched English (PubMed, Web of Science) and Chinese (CNKI and WanFang database) databases for relevant articles. The summarized effect sizes and 95% confidence intervals (CIs) were calculated by pooling estimates using the random-effects model. Egger's test was used to estimate publication bias. Heterogeneity among studies was indicated by p-values and I². Finally, we conducted subgroup analyses to elucidate the causes of heterogeneity. Thirteen studies were included in this meta-analysis. A positive association between maternal exposure to heavy metals and CHDs was found. Pooling odds ratios (ORs) for arsenic, cadmium, mercury, and lead were 2.12, 1.30, 1.22, and 2.30, respectively for total CHDs. Regarding CHD subtypes, arsenic was associated with an increased risk of septal defects (OR: 1.82), barium with left ventricular outflow tract obstruction (LVOTO) (OR: 1.15) and septal defects (OR: 1.21), and lead with conotruncal defects (OR: 2.34) and LVOTO (OR: 1.93). A heterogeneous relationship was found between studies using different methods of measurement, which were mainly due to differences in actual exposure levels to heavy metals. This meta-analysis suggests significant associations between arsenic, cadmium, mercury, and lead exposure during pregnancy and an increased risk of specific CHDs in offspring. These findings underscore the importance of heavy metal exposure during pregnancy in the risk of CHDs in offspring.

Relationship between cumulative exposure to metal mixtures and heart rate among Chinese preschoolers

The cumulative exposure to metals affects cardiac conduction, and the effect of polymetallic exposure on heart rate in children is unknown. To evaluate the relationship between cumulative exposure to metal mixtures and heart rate among Chinese preschoolers, the determination of urinary 24 metals was processed by high-resolution inductively coupled plasma-mass spectrometry. Heart rate was recorded when measuring blood pressure after resting 5 min or longer. As a method to compute the Environmental risk score (ERS) according to heart rate under heavy metal mixtures, adaptive elastic net (AENET) with 299 predictors which were formed by the combination of main effects, squared terms, and pairwise interactions of heavy metals with a total number of 23, 23, 253 respectively. To further assess the associations between ERS and heart rate, regression analyses were performed with complex survey designs. The construction of ERS under heart rate-related metal mixtures was returned by AENET in according to 11 main effects (tin, arsenic, zinc, iron, titanium, vanadium, nickel, manganese, cobalt, copper and chromium) and 2 squared terms (tungsten and rubidium). A high correlation was monitored between the alteration of ERS in the study population and heart rate (β = 1.030, 95% CI: 0.730 - 1.330 in 1239; β = 1.085, 95% CI: 0.777 - 1.393 in 1061). Significant associations of ERS with higher heart rates were also pointed out (Ps < 0.05). Our study elucidates the association of the cumulative exposure of heavy metals as mixtures and heart rate among Chinese preschoolers. Further research is obliged to corroborate these findings in longitudinal studies.

Advanced human developmental toxicity and teratogenicity assessment using human organoid models

Tremendous progress has been made in the field of toxicology leading to the advance of developmental toxicity assessment. Conventional animal models and in vitro two-dimensional models cannot accurately describe toxic effects and predict actual in vivo responses due to obvious inter-species differences between humans and animals, as well as the lack of a physiologically relevant tissue microenvironment. Human embryonic stem cell (hESC)- and induced pluripotent stem cell (iPSC)-derived three-dimensional organoids are ideal complex and multicellular organotypic models, which are indispensable in recapitulating morphogenesis, cellular interactions, and molecular processes of early human organ development. Recently, human organoids have been used for drug discovery, chemical toxicity and safety in vitro assessment. This review discusses the recent advances in the use of human organoid models, (i.e., brain, retinal, cardiac, liver, kidney, lung, and intestinal organoid models) for developmental toxicity and teratogenicity assessment of distinct tissues/organs following exposure to pharmaceutical compounds, heavy metals, persistent organic pollutants, nanomaterials, and ambient air pollutants. Combining next-generation organoid models with innovative engineering technologies generates novel and powerful tools for developmental toxicity and teratogenicity assessment, and the rapid progress in this field is expected to continue.

Prenatal metal(loid) mixtures and birth weight for gestational age: A pooled analysis of three cohorts participating in the ECHO program

BACKGROUND

A growing number of studies have identified both toxic and essential metals which influence fetal growth. However, most studies have conducted single-cohort analyses, which are often limited by narrow exposure ranges, and evaluated metals individually. The objective of the current study was to conduct an environmental mixture analysis of metal impacts on fetal growth, pooling data from three geographically and demographically diverse cohorts in the United States participating in the Environmental Influences on Child Health Outcomes program.

METHODS

The pooled sample (N = 1,002) included participants from the MADRES, NHBCS, and PROTECT cohorts. Associations between seven metals (antimony, cadmium, cobalt, mercury, molybdenum, nickel, tin) measured in maternal urine samples collected during pregnancy (median: 16.0 weeks gestation) and birth weight for gestational age z-scores (BW for GA) were investigated using Bayesian Kernel Machine Regression (BKMR). Models were also stratified by cohort and infant sex to investigate possible heterogeneity. Chromium and uranium concentrations fell below the limits of detection for most participants and were evaluated separately as binary variables using pooled linear regression models.

RESULTS

In the pooled BKMR analysis, antimony, mercury, and tin were inversely and linearly associated with BW for GA, while a positive linear association was identified for nickel. The inverse association between antimony and BW for GA was observed in both males and females and for all three cohorts but was strongest for MADRES, a predominantly low-income Hispanic cohort in Los Angeles. A reverse j-shaped association was identified between cobalt and BW for GA, which was driven by female infants. Pooled associations were null for cadmium, chromium, molybdenum, and uranium, and BKMR did not identify potential interactions between metal pairs.

CONCLUSIONS

Findings suggest that antimony, an understudied metalloid, may adversely impact fetal growth. Cohort- and/or sex-dependent associations were identified for many of the metals, which merit additional investigation.

Environmental pollution, a hidden culprit for health issues

The environmental and health impacts from the massive discharge of chemicals and subsequent pollution have been gaining increasing public concern. The unintended exposure to different pollutants, such as heavy metals, air pollutants and organic chemicals, may cause diverse deleterious effects on human bodies, resulting in the incidence and progression of different diseases. The article reviewed the outbreak of environmental pollution-related public health emergencies, the epidemiological evidence on certain pollution-correlated health effects, and the pathological studies on specific pollutant exposure. By recalling the notable historical life-threatening disasters incurred by local chemical pollution, the damning evidence was presented to criminate certain pollutants as the main culprit for the given health issues. The epidemiological data on the prevalence of some common diseases revealed a variety of environmental pollutants to blame, such as endocrine-disrupting chemicals (EDCs), fine particulate matters (PMs) and heavy metals. The retrospection of toxicological studies provided illustrative clues for evaluating ambient pollutant-induced health risks. Overall, environmental pollution, as the hidden culprit, should answer for the increasing public health burden, and more efforts are highly encouraged to strive to explore the cause-and-effect relationships through extensive epidemiological and pathological studies.

Urinary metals and maternal circulating extracellular vesicle microRNA in the MADRES pregnancy cohort

Exposure to metals increases risk for pregnancy complications. Extracellular vesicle (EV) miRNA contribute to maternal-foetal communication and are dysregulated in pregnancy complications. However, metal impacts on maternal circulating EV miRNA during pregnancy are unknown. Our objective was to investigate the impact of multiple metal exposures on EV miRNA in maternal circulation during pregnancy in the MADRES Study. Associations between urinary concentrations of nine metals and 106 EV miRNA in maternal plasma during pregnancy were investigated using robust linear regression (N = 231). Primary analyses focused on metal-miRNA associations in early pregnancy (median: 12.3 weeks gestation). In secondary analyses, we investigated associations with late pregnancy miRNA counts (median: 31.8 weeks gestation) in a subset of participants (N = 184) with paired measures. MiRNA associated with three or more metals (P_FDR<0.05) were further investigated using Bayesian Kernel Machine Regression (BKMR), an environmental mixture method. Thirty-five miRNA were associated (P_FDR<0.05) with at least one metal in early pregnancy. One association (an inverse association between cobalt and miR-150-5p) remained statistically significant when evaluating late pregnancy miRNA counts. Eight miRNA (miR-302b-3p, miR-199a-5p, miR-188-5p, miR-138-5p, miR-212-3p, miR-608, miR-1272, miR-19b-3p) were associated with three metals (barium, mercury, and thallium) in early pregnancy, and their predicted target genes were enriched in pathways important for placental development. Results were consistent when using BKMR. Early pregnancy exposure to barium, mercury, and thallium may have short-term impacts on a common set of EV miRNA which target pathways important for placental development.

Placental cadmium, placental genetic variations, and birth size

BACKGROUND

Maternal cadmium (Cd) burden has been associated with offspring birth size measures, yet associations of placental Cd with birth size are less clear. Further, the role of genetics in these associations has not been examined. We investigated associations of placental Cd with birth size and placental genotypes. We also examined the potential role of placental genotypes as modifiers of placental Cd and birth size associations.

METHODS

Participants were 490 mother-child pairs from the Omega and Placenta Microarray studies based in Seattle, WA. Placental Cd was measured using Agilent 7500 ICP-MS. The birth size was characterized using birth weight (BW), ponderal index (PI), and head circumference (HC). Eleven placental single nucleotide polymorphisms (SNPs) related to metal transport, growth regulation, endocrine response, and cell signaling were genotyped. Adjusted multivariable linear regression models were used to examine overall and sex-specific associations of placental Cd with birth size (BW, PI and HC), as well as associations of placental genotypes with placental Cd. Effect modification of placenta Cd and birth size associations by placental SNPs was examined using interaction terms and stratified analyses.

RESULTS

Mean maternal age was 33.6 years (SD = 4.4). Mean and median placental Cd levels were 4.0 ng/g tissue (SD = 2.7 ng/g tissue) and 3.6 ng/g (IQR 2.5 - 5.2 ng/g), respectively. Overall, compared with infants in the lowest quartile for placental Cd, infants in the second (ß = -102.8 g, 95% CI: -220.7, 15.1), third (ß = -83.2 g, 95% CI: -199.3, 32.9) and fourth (ß = -109.2 g, 95% CI: -225.4, 7.1) quartiles had lower BW, though associations were not statistically significant (all p-values > .05, trend p-value = .11). Among male infants, infants in the second (ß = -203.3 g, 95% CI: -379.7, -27.0) and fourth quartiles (ß = -198.3 g, 95% CI: -364.2, -32.5) had lower BW compared with those in the first quartiles (p-values < .05, trend p-value = .08). Similar relationships were not observed among female infants, though infant sex-placental Cd interaction terms were not significant. Similarly, male, but not female, infants had marginally significant positive associations between placental Cd and ponderal index (trend p-value = .06). The minor rs3811647 allele of the placental transferrin gene (NCBI Gene ID: 7018) was associated with an increase in Cd among all infants (p-value = .04). We did not find differences in associations of placental Cd with birth size markers among infants stratified by rs3811647 genotype.

CONCLUSIONS

Placental Cd was inversely associated with BW among male infants. The rs3811647 SNP of the transferrin gene was associated with placental Cd.

Systematic review and meta-analysis on the association between seasonal variation and gestational diabetes mellitus

Recently, there is growing evidence that ambient temperature and seasonal changes are related to the incidence of gestational diabetes mellitus (GDM). Thereby, this study was conducted to evaluate the association between seasonal changes and ambient temperature and GDM. We conducted a systematic search in PubMed, ISI Web of Science, Scopus, Google Scholar, and Cochrane Collaboration for human studies available until the end of 2020. We used the following keywords to identify relevant articles: "Diabetes, Gestational" (MeSH), "Glucose Tolerance Test" (MeSH), "Glucose intolerance" (MeSH), "Pregnancy outcome" (MeSH), "Birth outcome", "Seasons" (MeSH), "Weather" (MeSH), "Ambient Temperature," "Climate Change" (MeSH). Meta-analyses by using STATA software were conducted for analyzing data. Due to the high heterogeneity between included studies, a random-effects model was used. Subgroup analysis, meta-regression, and sensitivity analysis were used to define a source of heterogeneity. We found 13 studies related to the association between ambient temperature and season changes and GDM, which 11 of them were included in meta-analyses. Despite inconsistencies in outcome assessment across studies, we found a significant positive association between seasons of GDM screening and risk of GDM (pooled OR=1.12; 95% CI (1.03, 1.21)). The funnel plot and Egger's test showed that there was no significant publication bias among these studies (p=0.51). In general, season changes showed a significant positive relationship with prevalence of GDM. However, due to the unknown exact mechanism on this association, further studies should be conducted.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children

BACKGROUND

Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited.

OBJECTIVES

We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were ≥18 years of age with an ultrasound-confirmed singleton pregnancy of ≤16wk gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters.

RESULTS

Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] IQR=2.51} was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: -0.25, -0.02) and a 0.17-SD decrease in mean head circumference (95% CI: -0.28, -0.05), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] IQR=0.69} was associated with a 0.07-SD decrease in mean birth weight (95% CI: -0.15, 0.002).

DISCUSSION

Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502.

Increased apoptosis, reduced Wnt/β-catenin signaling, and altered tail development in zebrafish embryos exposed to a human-relevant chemical mixture

A wide variety of anthropogenic chemicals is detected in humans and wildlife and the health effects of various chemical exposures are not well understood. Early life stages are generally the most susceptible to chemical disruption and developmental exposure can cause disease in adulthood, but the mechanistic understanding of such effects is poor. Within the EU project EDC-MixRisk, a chemical mixture (Mixture G) was identified in the Swedish pregnancy cohort SELMA by the inverse association between levels in women at around gestational week ten with birth weight of their children. This mixture was composed of mono-ethyl phthalate, mono-butyl phthalate, mono-benzyl phthalate, mono-ethylhexyl phthalate, mono-isononyl phthalate, triclosan, perfluorohexane sulfonate, perfluorooctanoic acid, and perfluorooctane sulfonate. In a series of experimental studies, we characterized effects of Mixture G on early development in zebrafish models. Here, we studied apoptosis and Wnt/β-catenin signaling which are two evolutionarily conserved signaling pathways of crucial importance during development. We determined effects on apoptosis by measuring TUNEL staining, caspase-3 activity, and acridine orange staining in wildtype zebrafish embryos, while Wnt/β-catenin signaling was assayed using a transgenic line expressing an EGFP reporter at β-catenin-regulated promoters. We found that Mixture G increased apoptosis, suppressed Wnt/β-catenin signaling in the caudal fin, and altered the shape of the caudal fin at water concentrations only 20-100 times higher than the geometric mean serum concentration in the human cohort. These findings call for awareness that pollutant mixtures like mixture G may interfere with a variety of developmental processes, possibly resulting in adverse health effects.

Associations of prenatal heavy metals exposure with placental characteristics and birth weight in Hangzhou Birth Cohort: Multi-pollutant models based on elastic net regression

BACKGROUND

The human placenta is vulnerable to environmental pollutants, but the associations between exposure to multiple, correlated metals and placental characteristics have not been studied.

METHODS

The current study population was derived from the Hangzhou Birth Cohort Study. Whole blood and urine samples were collected from mothers during 20-28 gestational week. The concentrations of 11 metals in blood and 11 metals in urine were evaluated by inductively coupled plasma mass spectrometry. The data on placental characteristics and birth weight were retrieved from medical records. The elastic net (ENET) model combined with unpenalized regression model was employed to estimate the relationship between levels of metals and placental characteristics (placental weight, chorionic disc area, chorionic disc eccentricity, placental thickness, placental-fetal birth weight ratio) and birth weight. Mediation analysis was performed to explore the mediated effect of placenta on the association of prenatal metals exposure with birth weight.

RESULTS

Among 512 participants with urine metal levels, the ENET model retained Cadmium (Cd) and Selenium (Se) for placental weight. Further unpenalized regression model including Cd and Se simultaneously showed that one-unite increased natural-logarithm (ln)-transformed urine creatinine corrected (CC) Cd levels was associated with reductions in placental weight of -7.2 g (95% confidence interval (CI): -14.0, -0.4). Among 483 participants with blood metal levels, similarly, blood Cd levels were negatively associated with placental weight (β = -7.5, 95% CI: -17.0, 1.9). Furthermore, mediation analysis demonstrated that urine CC-Cd level was associated with a 21.3 g decrease (95% CI: -42.0, -2.5, p = 0.024) in birth weight through a reduction in placental weight, while blood Cd levels presented a negative association at borderline significance.

CONCLUSION

Our findings suggest a mediation effect of the placenta in the relationship between prenatal Cd exposure and lower birth weight. Additional studies with repeated assessment of exposure and more placental parameters are warranted to confirm this relationship.

Prenatal Metal Mixtures and Birth Weight for Gestational Age in a Predominately Lower-Income Hispanic Pregnancy Cohort in Los Angeles

BACKGROUND

Reduced fetal growth increases the risk for adverse health outcomes. Growing evidence suggests that metal exposures contribute to reduced fetal growth, but little is known about the effects of complex metal mixtures.

OBJECTIVES

We investigated the impact of a complex mixture of metals on birth weight for gestational age (BW for GA) in the Maternal and Developmental Risks from Environmental and Social Stressors study, a predominately lower-income Hispanic pregnancy cohort in Los Angeles, California.

METHODS

Cadmium (Cd), cobalt (Co), mercury (Hg), nickel (Ni), molybdenum (Mo), lead (Pb), antimony (Sb), tin (Sn), and thallium (Tl) were measured by inductively coupled plasma mass spectrometry (ICP-MS) in maternal urine samples collected in early pregnancy (median GA: 13.1 wk). Speciated urinary arsenic (As) (inorganic+monomethyl+dimethyl As) was measured by high-performance liquid chromatography coupled to ICP-MS. Primary analyses focused on a mixture of seven metals that have previously been associated individually with fetal growth (i.e., As, Cd, Co, Hg, Ni, Pb, Tl) (n=262). In exploratory analyses, we additionally examined three metals that have been less studied in relation to fetal growth (i.e., Mo, Sb, Sn). Covariate-adjusted Bayesian kernel machine regression was used to investigate metal mixture associations with BW for GA z-scores.

RESULTS

In primary analyses, Hg and Ni ranked highest as predictors of BW for GA. An inverse linear association was estimated for Hg, whereas a positive association was estimated for Ni at low-to-moderate concentrations. A potential interaction between Hg and Ni was also identified. In our exploratory analysis, Sb ranked highest as a predictor of BW for GA, followed by Hg and Ni.

CONCLUSIONS

Our findings suggest that in this understudied population, Hg may reduce fetal growth, whereas Ni may promote fetal growth. We also identified Sb as a potential metal of concern for this population, which merits additional investigation. https://doi.org/10.1289/EHP7201.

Low-level maternal exposure to cadmium, lead, and mercury and birth outcomes in a Swedish prospective birth-cohort

Observational studies have indicated that low-to-moderate exposure to cadmium (Cd), lead (Pb), and mercury (Hg) adversely affects birth anthropometry, but results are inconclusive. The aim of this study was to elucidate potential impact on birth anthropometry of exposure to Cd, Pb, and Hg in pregnant women, and to identify the main dietary sources. In the NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment) birth-cohort in northern Sweden, blood and urine were collected from pregnant women in early third trimester. Cd, Pb and Hg were measured in erythrocytes (n = 584), and Cd also in urine (n = 581), by inductively coupled plasma mass spectrometry. Dietary data were collected through a semi-quantitative food frequency questionnaire administered in mid-third trimester. Birth anthropometry data were extracted from hospital records. In multivariable-adjusted spline regression models, a doubling of maternal erythrocyte Cd (median: 0.29 μg/kg) above the spline knot of 0.50 μg/kg was associated with reduced birth weight (B: -191 g; 95% CI: -315, -68) and length (-0.67 cm; -1.2, -0.14). The association with birth weight remained when the analysis was restricted to never-smokers. Likewise, a doubling of erythrocyte Hg (median 1.5 μg/kg, mainly MeHg) above 1.0 μg/kg, was associated with decreased birth weight (-59 g; -115, -3.0), and length (-0.29 cm; -0.54, -0.047). Maternal Pb (median 11 μg/kg) was unrelated to birth weight and length. Erythrocyte Cd was primarily associated with intake of plant derived foods, Pb with game meat, tea and coffee, and Hg with fish. The results indicated that low-level maternal Cd and Hg exposure were associated with poorer birth anthropometry. Further prospective studies in low-level exposed populations are warranted.

The association between maternal exposure to organophosphate pesticides and neonatal anthropometric measures: A systematic review and meta-analysis

Background:

This study aimed to evaluate the epidemiological studies on the relationship between organophosphate (OP) pesticide exposure during pregnancy and neonatal anthropometric measures.

Materials and Methods:

In this systematic review and meta analyses, a comprehensive search of the literature for the association of maternal exposure to OP pesticides and birth outcome including birth weight, birth length, and head circumference was conducted from scientific databases of MEDLINE, Scopus, Web of Science, and Cochrane library until the end of April 2019. We used the following keyword to identify the relevant studies: “birth weight,” “birth length,” “pregnancy outcome,“”birth outcome,” “organophosphate pesticides,” and “organophosphate metabolites.” Only English language studies investigating the relationship between pregnant mothers' exposure to OP metabolites and birth outcomes were examined.

Results:

Of the 10 articles reviewed, eight studies used to assess the association with birth weight, as well as five, and six studies were used in meta analysis to determine the association between OP exposure and birth length and head circumference. Pooled estimates were performed using a fixed effects model or random effects model. No significant association was observed between maternal exposure to OPs and birth weight (β = 1.520;95% confidence interval [CI] [−10.781, 13.820]), birth length (β = −0.011; [−0.132, 0.109]), and head circumference (β =0.022; 95%CI [−0.06, 0.103]).

Conclusion:

Although the effect of maternal exposure to OP on the birth outcome is not completely clear, strategies should be adopted to control the use of these substances.

Interactions between Environmental Exposures and the Microbiome: Implications for Fetal Programming

Decades of population-based health outcomes data highlight the importance of understanding how environmental exposures in pregnancy affect maternal and neonatal outcomes. Animal model research and epidemiological studies have revealed that such exposures are able to alter fetal programming through stable changes in the epigenome, including altered DNA methylation patterns and histone modifications in the developing fetus and infant. It is similarly known that while microbes can biotransform environmental chemicals via conjugation and de-conjugation, specific exposures can also alter the community profile and function of the human microbiome. In this review, we consider how alterations to the maternal and or fetal/infant microbiome through environmental exposures could directly and indirectly alter fetal programming. We highlight two specific environmental exposures, cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs), and outline their effects on the developing fetus and the perinatal (maternal and fetal/infant) microbiome. We further consider how chemical exposures in the setting of natural disasters may be of particular importance to environmental health.