Fetal exposure to lead during pregnancy and the risk of preterm and early-term deliveries

Prenatal exposure to metal mixtures, body mass index trajectories in early life and effect modifiers: Insights from a prospective birth cohort study

Current scientific knowledge is insufficient on the effects of metal mixtures on early life growth trajectories. This study included 7118 mother-infant pairs from a Chinese birth cohort. Concentrations of 18 maternal urinary metals were quantified, and growth trajectories were conducted based on standardized body mass index (BMI) for up to eight times from 0 to 2 years. A three-phase analytical framework was applied to explore the risk ratios (RR) and 95 % confidence intervals (95 % CI) of co-exposure to metals on dynamic growth, along with potential modifiers. Five growth trajectory groups were identified. Exposure to metal mixtures driven by thallium (Tl, 34.8 %) and aluminum (Al, 16.2 %) was associated with an increased risk of low-rising trajectory (RR=1.58, 95 % CI: 1.25, 2.00); however, exposure to mixtures driven by strontium (Sr, 49.5 %) exhibited an inverse correlation (RR = 0.81, 95 % CI: 0.67, 0.97). Furthermore, infants with varying levels of Tl, Al and Sr, as well as modifiers including pre-pregnancy BMI and infant sex faced distinct risks of low-rising trajectory. Our findings highlighted the Tl, Al, and Sr as key metals in relation to the low-rising trajectory in early life characterized as catch-up growth, with pre-pregnancy BMI and infant sex exerting as potential modifiers.

Associations of maternal blood metal concentrations with plasma eicosanoids among pregnant women in Puerto Rico

BACKGROUND/AIM

Heavy metals are known to induce oxidative stress and inflammation, and the association between metal exposure and adverse birth outcomes is well established. However, there lacks research on biomarker profiles linking metal exposures and adverse birth outcomes. Eicosanoids are lipid molecules that regulate inflammation in the body, and there is growing evidence that suggests associations between plasma eicosanoids and pregnancy outcomes. Eicosanoids may aid our understanding of etiologic birth pathways. Here, we assessed associations between maternal blood metal concentrations with eicosanoid profiles among 654 pregnant women in the Puerto Rico PROTECT birth cohort.

METHODS

We measured concentrations of 11 metals in whole blood collected at median 18 and 26 weeks of pregnancy, and eicosanoid profiles measured in plasma collected at median 26 weeks. Multivariable linear models were used to regress eicosanoids on metals concentrations. Effect modification by infant sex was explored using interaction terms.

RESULTS

A total of 55 eicosanoids were profiled. Notably, 12-oxoeicosatetraenoic acid (12-oxoETE) and 15-oxoeicosatetraenoic acid (15-oxoETE), both of which exert inflammatory activities, had the greatest number of significant associations with metal concentrations. These eicosanoids were associated with increased concentrations of Cu, Mn, and Zn, and decreased concentrations of Cd, Co, Ni, and Pb, with the strongest effect sizes observed for 12-oxoETE and Pb (β:-33.5,95 %CI:-42.9,-22.6) and 15-oxoETE and Sn (β:43.2,95 %CI:11.4,84.1). Also, we observed differences in metals-eicosanoid associations by infant sex. Particularly, Cs and Mn had the most infant sex-specific significant associations with eicosanoids, which were primarily driven by female fetuses. All significant sex-specific associations with Cs were inverse among females, while significant sex-specific associations with Mn among females were positive within the cyclooxygenase group but inverse among the lipoxygenase group.

CONCLUSION

Certain metals were significantly associated with eicosanoids that are responsible for regulating inflammatory responses. Eicosanoid-metal associations may suggest a role for eicosanoids in mediating metal-induced adverse birth outcomes.

Associations between prenatal multiple plasma metal exposure and newborn telomere length: Effect modification by maternal age and infant sex

Exposure to metals during pregnancy may affect maternal and infant health. However, studies on the combined effects of metals on the telomere length (TL) of newborns are limited. A prospective cohort study was conducted among 1313 mother-newborn pairs in the Guangxi Zhuang Birth Cohort. The concentrations of metals in maternal plasma during the first trimester were measured using inductively coupled plasma-mass spectrometry. We explored the associations between nine plasma metals and newborn TL using generalized linear models (GLMs), principal component analysis (PCA), quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR). The GLMs revealed the inverse association between plasma arsenic (percent change, -5.56%; 95% CI: -7.69%, -3.38%) and barium concentrations (-9.84%; 95% CI: -13.81%, -5.68%) and newborn TL. Lead levels were related to significant decreases in newborn TL only in females. The PCA revealed a negative association between the PC3 and newborn TL (-4.52%; 95% CI: -6.34%, -2.68%). In the BKMR, the joint effect of metals was negatively associated with newborn TL. Qgcomp indicated that each one-tertile increase in metal mixture levels was associated with shorter newborn TL (-9.39%; 95% CI: -14.32%, -4.18%). The single and joint effects of multiple metals were more pronounced among pregnant women carrying female fetuses and among pregnant women <28 years of age. The finding suggests that prenatal exposure to arsenic, barium, antimony, and lead and mixed metals may shorten newborn TLs. The relationship between metal exposures and newborn TL may exhibit heterogeneities according to infant sex and maternal age.

Environmental and occupational exposure of metals and female reproductive health

Untainted environment promotes health, but the last few decades experienced steep upsurge in environmental contaminants posing detrimental physiological impact. The responsible factors mainly include the exponential growth of human population, havoc rise in industrialization, poorly planned urbanization, and slapdash environment management. Environmental degradation can increase the likelihood of human exposure to heavy metals, resulting in health consequences such as reproductive problems. As a result, research into metal-induced causes of reproductive impairment at the genetic, epigenetic, and biochemical levels must be strengthened further. These metals impact upon the female reproduction at all strata of its regulation and functions, be it development, maturation, or endocrine functions, and are linked to an increase in the causes of infertility in women. Chronic exposures to the heavy metals may lead to breast cancer, endometriosis, endometrial cancer, menstrual disorders, and spontaneous abortions, as well as pre-term deliveries, stillbirths. For example, endometriosis, endometrial cancer, and spontaneous abortions are all caused by the metalloestrogen cadmium (Cd); lead (Pb) levels over a certain threshold can cause spontaneous abortion and have a teratogenic impact; toxic amounts of mercury (Hg) have an influence on the menstrual cycle, which can lead to infertility. Impact of environmental exposure to heavy metals on female fertility is therefore a well-known fact. Thus, the underlying mechanisms must be explained and periodically updated, given the growing evidence on the influence of increasing environmental heavy metal load on female fertility. The purpose of this review is to give a concise overview of how heavy metal affects female reproductive health.

Trends of Blood Lead Levels in US Pregnant Women: The National Health and Nutrition Examination Survey (2001–2018)

Objectives

This study investigates the trends of blood lead levels in US pregnant women based on the National Health and Nutrition Examination Survey from 2001 to 2018.

Methods

A total of 1,230 pregnant women were included in this study. The weighted logistic regression was applied to analyze the association between sociodemographic characteristics with high blood levels. We computed the blood lead levels for each survey period from 2001–2002 to 2017–2018. Moreover, we used the adjusted linear regression model to investigate the time-related change in blood lead level. The odds ratio (OR) with a 95% confidence interval (CI) was calculated accordingly.

Results

The mean blood lead was 0.73 ± 0.03 ug/dL, and high blood lead was observed in 2.53% of individuals. The Mexican Americans were more associated with high blood lead than the non-Hispanic white (OR, 1.072; 95% CI, 1.032-1.112). The mean blood lead level has decreased from 0.97 ug/dL in 2001–2002 to 0.46 ug/dL in 2013–2014. Afterward, a slight increase was observed with the mean blood lead of 0.55 ug/dL in 2015–2016 and 0.53 ug/dL in 2017-2018. In the adjusted linear regression model, each year's increase would lead to a 0.029 ug/dL decrease in blood lead (P < 0.001). However, no significant change was observed in the 2017–2018 cycle compared with 2009–2010 (P = 0.218).

Conclusion

This study summarized the trend of blood lead levels in US pregnant women over 2001–2018. Continued effort is still required to control lead sources better and protect this population from lead exposure.

A Data Mining Approach Reveals Chemicals Detected at Higher Levels in Non-Hispanic Black Women Target Preterm Birth Genes and Pathways

Preterm birth occurs disproportionately in the USA non-Hispanic Black population. Black women also face disproportionate exposure to certain environmental chemicals. The goal of this study was to use publicly available toxicogenomic data to identify chemical exposures that may contribute to preterm birth disparities. We tested 19 chemicals observed at higher levels in the blood or urine of non-Hispanic Black women compared to non-Hispanic White women. We obtained chemical-gene interactions from the Comparative Toxicogenomics Database and a list of genes involved in preterm birth from the Preterm Birth Database. We tested chemicals for enrichment with preterm birth genes using chi-squared tests. We then conducted pathway enrichment analysis for the preterm birth genes using DAVID software and identified chemical impacts on genes involved in these pathways. Genes annotated to all 19 chemicals were enriched with preterm birth genes (FDR-adjusted p value < 0.05). Preterm birth enriched chemicals that were detected at the highest levels in non-Hispanic Black women included methyl mercury, methylparaben, propylparaben, diethyl phthalate, dichlorodiphenyldichloroethylene, and bisphenol S. The preterm birth genes were enriched for pathways including "inflammatory response" (FDR-adjusted p value = 3 × 10-19), "aging" (FDR-adjusted p value = 4 × 10-8) and "response to estradiol" (FDR-adjusted p value = 2 × 10-4). Chemicals enriched with preterm birth genes impacted genes in all three pathways. This study adds to the body of knowledge suggesting that exposures to environmental chemicals contribute to racial disparities in preterm birth and that multiple chemicals drive these effects. These chemicals affect genes involved in biological processes relevant to preterm birth such as inflammation, aging, and estradiol pathways.

Maternal Metals/Metalloid Blood Levels Are Associated With Lipidomic Profiles Among Pregnant Women in Puerto Rico

Background/Aim: The association between heavy metal exposure and adverse birth outcomes is well-established. However, there is a paucity of research identifying biomarker profiles that may improve the early detection of heavy metal-induced adverse birth outcomes. Because lipids are abundant in our body and associated with important signaling pathways, we assessed associations between maternal metals/metalloid blood levels with lipidomic profiles among 83 pregnant women in the Puerto Rico PROTECT birth cohort.

Methods: We measured 10 metals/metalloid blood levels during 24–28 weeks of pregnancy. Prenatal plasma lipidomic profiles were identified by liquid chromatography–mass spectrometry-based shotgun lipidomics. We derived sums for each lipid class and sums for each lipid sub-class (saturated, monounsaturated, polyunsaturated), which were then regressed on metals/metalloid. False discovery rate (FDR) adjusted p-values (q-values) were used to account for multiple comparisons.

Results: A total of 587 unique lipids from 19 lipid classes were profiled. When controlling for multiple comparisons, we observed that maternal exposure to manganese and zinc were negatively associated with plasmenyl-phosphatidylethanolamine (PLPE), particularly those containing polyunsaturated fatty acid (PUFA) chains. In contrast to manganese and zinc, arsenic and mercury were positively associated with PLPE and plasmenyl-phosphatidylcholine (PLPC).

Conclusion: Certain metals were significantly associated with lipids that are responsible for the biophysical properties of the cell membrane and antioxidant defense in lipid peroxidation. This study highlighted lipid-metal associations and we anticipate that this study will open up new avenues for developing diagnostic tools.

Free Cortisol Mediates Associations of Maternal Urinary Heavy Metals with Neonatal Anthropometric Measures: A Cross-Sectional Study

Prenatal exposure to heavy metals is known to be associated with adverse birth outcomes and oxidative stress biomarkers. In this study, we examined whether maternal free cortisol or 8-Hydroxy-2-Deoxyguanosine (8-OHdG) could mediate associations between maternal heavy metal exposure and birth outcomes. A total of 182 healthy pregnant women were recruited. Heavy metals (including Pb, Hg, and Cd), free-cortisol, and 8-OHdG were analyzed in urine at delivery. Birth outcomes including birth weight, length, Ponderal index, and head circumference were measured. To examine associations of maternal urinary heavy metals with biomarkers and birth outcomes, generalized linear models were employed. Birth length was positively associated with Pb (β = 0.78, 95% CI: 0.09−1.46) and Hg (β = 0.84, 95% CI: 0.23−1.45) (both p < 0.05). The Ponderal index, a measure of a newborn’s leanness, was negatively associated with maternal urinary Pb (β = −0.23, 95% CI: −0.46−−0.07) and Hg (β = −0.26, 95% CI: −0.44−−0.08) (both p < 0.05). No association between maternal Cd and birth outcomes was observed. Most heavy metals showed positive associations with free cortisol and 8-OHdG. Free cortisol was identified as a mediator underlying the observed relationship between Hg and birth length or Ponderal index. This study observed adverse birth outcomes from maternal exposures to Pb and Hg. Increased free cortisol related to Hg exposure was suggested as a possible causal pathway from Hg exposure to birth outcomes such as the Ponderal index.

Associations between prenatal multiple metal exposure and preterm birth: Comparison of four statistical models

BACKGROUND

Exposure to some heavy metals has been demonstrated to be related to the risk of preterm birth (PTB). However, the effects of multi-metal mixture are seldom assessed. Thus, we aimed to investigate the associations of maternal exposure to metal mixture with PTB, and to identify the main contributors to PTB from the mixture.

METHODS

The population in the nested case-control study was from a prospective cohort enrolled in Wuhan, China between 2012 and 2014. Eighteen metals were measured in maternal urine collected before delivery. Logistic regression, elastic net regularization (ENET), weighted quantile sum regression (WQSR), and Bayesian kernel machine regression (BKMR) were used to estimate the overall effect and identify important mixture components that drive the associations with PTB.

RESULTS

Logistic regression found naturally log-transformed concentrations of 13 metals were positively associated with PTB after adjusting for the covariates, and only V, Zn, and Cr remained the significantly positive associations when additionally adjusting for the 13 metals together. ENET identified 11 important metals for PTB, and V (β = 0.23) had the strongest association. WQSR determined the positive combined effect of metal mixture on PTB (OR: 1.44, 95%CI: 1.32, 1.57), and selected Cr and V (weighted 0.41 and 0.32, respectively) as the most weighted metals. BKMR analysis confirmed the overall mixture was positively associated with PTB, and the independent effect of V was the most significant. Besides, BKMR showed the non-linear relationships of V and Cu with PTB, and the potential interaction between Zn and Cu.

CONCLUSION

Applying different statistical models, the study found that exposure to the metal mixture was associated with a higher risk of PTB, and V was identified as the most important risk factor among co-exposed metals for PTB.

Associations of maternal exposure to 41 metals/metalloids during early pregnancy with the risk of spontaneous preterm birth: Does oxidative stress or DNA methylation play a crucial role?

BACKGROUND

Few studies have explored the effects of multiple types of metals/metalloids on spontaneous preterm birth (SPB). A nested case-control study was conducted in Shanxi Province to investigate the associations between maternal exposure to 41 metals/metalloids during early pregnancy and the risk of SPB, and to clarify the underlying mechanisms of oxidative stress and DNA methylation.

METHODS

A total of 74 controls with full-term delivery and 74 cases with SPB were included in the nested case-control study. The metals/metalloids in serum and the DNA adducts in peripheral blood cell DNA were determined using ICP-MS and UPLC-QqQ-MS/MS, respectively. Unconditional logistic regression models were employed to estimate the associations of the risk of SPB with the metal concentrations, as well as with the levels of oxidative stress/DNA methylation. In addition, linear regression models were used to investigate the associations between the metal/metalloid concentrations and the levels of oxidative stress/DNA methylation.

RESULTS

After adjusting for potential confounders, the concentrations of Mn, Fe, Cu, Nd, Hg, and Pb in maternal serum during early pregnancy were positively associated with the risk of SPB. Compared with the lowest levels (Quartile 1) of Mn, Fe, Cu, Nd, Hg, and Pb, the odds ratios of SPB increased to 5.21 (95% CI: 1.63, 16.68), 3.47 (95% CI: 1.07, 11.21), 16.23 (95% CI: 3.86, 68.18), 10.54 (95% CI: 2.79, 39.86), 5.88 (95% CI: 1.72, 20.11), and 4.09 (95% CI: 1.31, 12.77) in the highest levels (Quartile 4), respectively. A significant increase in 8-OHdG was associated with the increased exposure to Fe, Pr, Eu, Er, and Lu. The levels of 5-MdC, 5-HmdC, and N6-MdA-the indicators of DNA methylation-were associated with exposure to multiple metals/metalloids. However, no significant associations were observed between the levels of oxidative stress or DNA methylation and the risk of SPB.

CONCLUSIONS

Exposure to multiple types of metals/metalloids during early pregnancy is positively associated with the risk of SPB. Oxidative stress and DNA methylation are significantly associated with exposure to multiple metals/metalloids. Systemic oxidative stress and DNA methylation have not been proven to be the mediating mechanisms of metals increasing the risk of SPB.

Maternal exposure to endocrine disrupting chemicals (EDCs) and preterm birth: A systematic review, meta-analysis, and meta-regression analysis

Preterm birth is the second most common cause of death in children under 5 years of age. The etiology of preterm birth has not yet been elucidated. Although maternal exposure to endocrine disrupting chemicals (EDCs) may increase the risk for preterm birth, associations have not been confirmed. We performed a meta-analysis to elucidate the relationships between maternal exposure to EDCs and preterm birth. A systematic search of PubMed, Ovid-EMBASE, and the Cochrane Library (CENTRAL) for relevant published studies providing quantitative data on the association between maternal EDC exposure and preterm birth in humans was conducted in July 2021. To calculate the overall estimates, we pooled the adjusted regression coefficients with 95% confidence intervals (CIs) from each study by the inverse variance method. A total of 59 studies were included. The pooled results indicated that maternal exposure to metals (OR, 1.23; 95% CI, 1.17 to 1.29) and phthalates (OR, 1.31; 95% CI, 1.21 to 1.42) was related to an increased risk for preterm birth. Specifically, maternal exposure to lead, cadmium, chromium, copper and manganese appeared to be correlated with an elevated risk for preterm birth. Additionally, maternal exposure to monoethyl phthalate (MEP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), monobenzyl phthalate (MBzP), and di (2-ethylhexyl) phthalate (DEHP) was also associated with preterm birth. In conclusion, maternal exposure to metals and phthalates may increase the risk for preterm birth based on current evidence.

Association between early-term birth and delayed neurodevelopment at the age of 2 years: results from a cohort study in China

A growing body of evidence indicates that early-term births (37-38 weeks of gestational age) have an increased risk of short-term and long-term complications. Here, we sought to explore the association between early-term births and the risk of delayed neurodevelopment at age 2 years. Pregnant women and their live singleton birth were recruited from a single tertiary hospital between October 2013 and February 2017. Mental and Psychomotor Development Indexes (MDI and PDI) were assessed using the Bayley Scales of Infant Development (BSID). Delayed neurodevelopment was defined as scores of PDI or MDI less than -1SD relative to the mean score of the study population. In total, 1678 full-term infants and 727 early-term infants were assessed when they were 2 years old. After adjustment for potential confounders, early-term birth was related to 43% increased odds of neurodevelopmental delay in the PDI domain as compared with full-term birth (OR: 1.43; 95% CI: 1.12, 1.82). The observed associations were more prominent among those infants born by cesarean (OR: 1.44; 95% CI: 1.03, 2.00) and among males (OR: 1.66; 95% CI: 1.20, 2.28). No statistical difference in the MDI domain was found between early-term and full-term births.Conclusions: Our findings suggest that early-term birth was associated with increased odds of delayed neurodevelopment in the PDI domain as measured by BSID assessments at age 2 years. Health professionals should be aware of the influence of early-term birth on the risk of delayed neurodevelopment. What is Known: • Evidence indicates that early-term births have an increased risk of short-term and long-term complications. • The association between early-term births and delayed neurodevelopment at their early childhood has not been widely studied. What is New: • Early-term birth was associated with increased odds of delayed neurodevelopment in PDI domain as measured by BSID assessments at age 2 years. • The observed associations were more prominent among infants born by cesarean section and among male infants.

Exposure to atmospheric metals using moss bioindicators and neonatal health outcomes in Portland, Oregon

Studying the impacts of prenatal atmospheric heavy-metal exposure is challenging, because biological exposure monitoring does not distinguish between specific sources, and high-resolution air monitoring data is lacking for heavy metals. Bioindicators - animal or plant species that can capture environmental quality - are a low-cost tool for evaluating exposure to atmospheric heavy-metal pollution that have received little attention in the public-health literature. We obtained birth records for Portland, Oregon live births (2008-2014) and modeled metal concentrations derived from 346 samples of moss bioindicators collected in 2013. Exposure estimates were assigned using mother's residential address at birth for six metals with known toxic and estrogenic effects (arsenic, cadmium, chromium, cobalt, nickel, lead). Associations were evaluated for continuous (cts) and quartile-based (Q) metal estimates and three birth outcomes (preterm birth (PTB; <37 weeks)), very PTB (vPTB; <32 weeks), small for gestational age (SGA; 10th percentile of weight by age and sex)) using logistic regression models with adjustment for demographic characteristics, and stratified by maternal race. Chromium and cobalt were associated with increased odds of vPTB (chromium - odds ratio (OR)_cts = 1.09, 95% CI: 1.00, 1.17; cobalt - OR_Q4vsQ1 = 1.33, 95% CI: 1.03, 1.71). Cobalt, chromium and cadmium were significantly associated with odds of SGA, although the direction of association differed by metal (cobalt - OR_cts = 1.04, 95% CI: 1.01, 1.07; chromium - OR_Q3vsQ1 = 0.91, 95% CI: 0.83, 0.99; cadmium - OR_cts = 0.96, 95% CI: 0.93, 1.00). In stratified analyses, odds of SGA were significantly different among non-white mothers compared to white mothers with exposure to chromium, cobalt, lead and nickel. This novel application of a moss-based exposure metric found that exposure to some atmospheric metals is associated with adverse birth outcomes. These findings are consistent with previous literature and suggest that moss bioindicators are a useful complement to traditional exposure-assessment methods.

Association of maternal lead exposure with the risk of preterm: a meta-analysis

BACKGROUND

The relationship between maternal lead level and risk of preterm birth (PTB) remained controversial. Therefore, herein we performed this meta-analysis to investigate the association of maternal blood, urine and cord blood lead level with the risk of PTB using observational studies.

METHODS

A systematic search was conducted in PubMed, EMBASE and Ovid Medline databases from inception to August 2019, and sixteen studies with 65600 participants investigating the association between maternal lead level and PTB were included in our meta-analysis. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the highest versus lowest lead level by random-effects model.

RESULTS

Overall, the pooled OR of all included articles for the highest versus lowest PTB score was 1.29 (95% CI = 1.14-1.46; I2 = 80.4%, p < .001), and the results revealed a direct and significant relationship between second and third trimester blood lead level (BLL) and PTB (OR 2nd trimester= 1.61, 95% CI = 1.08-2.40, OR 3rd trimester= 1.57, 95% CI = 1.11-2.23).

CONCLUSION

Results of this meta-analysis showed that maternal BLL is directly associated with the risk of PTB.

Maternal Urinary Metal and Metalloid Concentrations in Association with Oxidative Stress Biomarkers

Metal exposure has been associated with a wide range of adverse birth outcomes and oxidative stress is a leading hypothesis of the mechanism of action of metal toxicity. We assessed the relationship between maternal exposure to essential and non-essential metals and metalloids in pregnancy and oxidative stress markers, and sought to identify windows of vulnerability and effect modification by fetal sex. In our analysis of 215 women from the PROTECT birth cohort study, we measured 14 essential and non-essential metals in urine samples at three time points during pregnancy. The oxidative stress marker 8-iso-prostaglandin F2α (8-iso-PGF2α) and its metabolite 2,3-dinor-5,6-dihydro-15-15-F2t-IsoP, as well as prostaglandin F2α (PGF2α), were also measured in the same urine samples. Using linear mixed models, we examined the main effects of metals on markers of oxidative stress as well as the visit-specific and fetal sex-specific effects. After adjustment for covariates, we found that a few urinary metal concentrations, most notably cesium (Cs) and copper (Cu), were associated with higher 8-iso-PGF2α with effect estimates ranging from 7.3 to 14.9% for each interquartile range, increase in the metal concentration. The effect estimates were generally in the same direction at the three visits and a few were significant only among women carrying a male fetus. Our data show that higher urinary metal concentrations were associated with elevated biomarkers of oxidative stress. Our results also indicate a potential vulnerability of women carrying a male fetus.

Prenatal Environmental Metal Exposure and Preterm Birth: A Scoping Review

Preterm birth (PTB) and its complications are the leading causes of under-five year old child deaths, accounting worldwide for an estimated one million deaths annually. The etiology of PTB is complex and multifactorial. Exposures to environmental metals or metalloids are pervasive and prenatal exposures to them are considered important in the etiology of PTB. We conducted a scoping review to determine the extent of prenatal exposures to four metals/metalloids (lead, mercury, cadmium and arsenic) and their association with PTB. We reviewed original research studies published in PubMed, Embase, the Cochrane Library, Scopus, POPLINE and the WHO regional indexes from 2000 to 2019; 36 articles were retained for full text review. We documented a higher incidence of PTB with lead and cadmium exposures. The findings for mercury and arsenic exposures were inconclusive. Metal-induced oxidative stress in the placenta, epigenetic modification, inflammation, and endocrine disruptions are the most common pathways through which heavy metals and metalloids affect placental functions leading to PTB. Most of the studies were from the high-income countries, reflecting the need for additional data from low-middle-income countries, where PTB rates are higher and prenatal exposure to metals are likely to be just as high, if not higher.

Developmental toxicity of endocrine-disrupting chemicals: Challenges and future directions

Maternal exposure to a mixture of various endocrine disruptors (EDCs) may have a substantial impact on postnatal health of her offspring(s) and increase the risk for health disorders and diseases in adulthood. Research efforts to better understand the health risk associated with endocrine disruptor exposures in early life have increased in recent decades. This paper provides a short overview of the current challenges that researchers continue to face in selecting appropriate epidemiologic methods and study designs to identify endocrine disruptors and evaluate their adverse health effects during this critical developmental window. Major challenges involve the selection of a representative biomarker that reflects the foetal internal dose of the biologically active chemical or its metabolite(s) that may be associated with adverse health effects with regard to variable level and duration of exposure and the latency between exposure and disorder/disease manifestation. Future studies should pay more attention to identifying factors that contribute to interindividual variability in susceptibility to various EDCs and other toxicants.

Associations between prenatal and postnatal lead exposure and preschool children humoral and cellular immune responses

Studies have shown that lead exposure affected the immune function, but few studies have examined the relationships between in utero lead exposure, a sensitive period that is important for immune development, and later immune responses. To investigate the effects of prenatal and childhood lead exposure on the preschool-aged children's immune responses, a prospective birth cohort study was established in Wuhan, China, in which lead concentrations were analyzed in maternal urine during the third trimester and in plasma samples from children aged about 3 years. We assessed immune responses by measuring immune cytokines in the children's plasma (n = 326) and peripheral blood T lymphocyte subsets (n = 394) at 3 years of age. Each unit increase in maternal urinary lead concentration (μg/g creatinine) was associated with reduced IL-10 (β = -5.93%, 95%CI: -11.82%, -0.03%) and reduced IL-4 levels (β = -5.62%, 95%CI: -10.44%, -0.80%). Lead in children's plasma (μg/L) was associated with significant increase in TNF-α (β = 10.78%, 95%CI: 3.97%, 17.59%). No statistically significant relationship of childhood lead exposure with T lymphocyte subsets was observed. The study suggested prenatal and childhood lead exposure was associated with changes in preschool children's plasma cytokine levels.

Developmental Exposure to Air Pollution, Cigarettes, and Lead: Implications for Brain Aging

Brain development is impaired by maternal exposure to airborne toxins from ambient air pollution, cigarette smoke, and lead. Shared postnatal consequences include gray matter deficits and abnormal behaviors as well as elevated blood pressure. These unexpectedly broad convergences have implications for later life brain health because these same airborne toxins accelerate brain aging. Gene-environment interactions are shown for ApoE alleles that influence the risk of Alzheimer disease. The multigenerational trace of these toxins extends before fertilization because egg cells are formed in the grandmaternal uterus. The lineage and sex-specific effects of grandmaternal exposure to lead and cigarettes indicate epigenetic processes of relevance to future generations from our current and recent exposure to airborne toxins.

Associations of maternal ambient temperature exposures during pregnancy with the risk of preterm birth and the effect modification of birth order during the new baby boom: A birth cohort study in Guangzhou, China

Maternal exposures to ambient temperatures during pregnancy may increase the preterm birth (PTB) risk; however, which periods have stronger effects remain controversial. The effects of temperature exposure on PTB in first- and second-born neonate groups may be different during the new baby boom that has followed the Two-child Policy in China. We examined a birth cohort of 4928 pregnant women beginning in 2016 in Guangzhou, China. An inverse distance weighted method was used to estimate the temperature exposure at each individual residential address. A distribution lag non-linear model incorporating a Cox proportional hazard model was employed to estimate the effects of temperature exposure on PTB and test the effects modification of birth order related to the new baby boom. A total of 4101 pregnant women were included, of which 234 (5.7%) experienced PTB. Compared with the mean temperature (23.0 °C), we found a significantly higher risks of PTB associated with high temperatures (i.e, 30 °C [95th centile]) from the 4th to 8th, and 22nd to 27th gestational weeks. A peak effect was found during the 6th week (HR = 1.79, 95% CI: 1.26, 2.54) and 24th week (HR = 1.83, 95% CI: 1.27, 2.62). The risks of PTB were reduced for low temperatures (i.e. 14 °C [5th centile] versus 23.0 °C) from the 2nd to 10th and 20th to 26th gestational weeks, and the negative peak effect was found during the 4th week (HR = 0.43, 95% CI: 0.26, 0.72) and 23rd week (HR = 0.59, 95% CI: 0.43, 0.83). Stratification analyses showed that significant effects of 30 °C versus 23 °C on PTB were observed during the 4th to 8th weeks in the second-born neonate, and the peak effect was found in the 6th week (HR = 2.13, 95% CI: 1.31, 3.47). However, we did not find significant effects of 30 °C during the same weeks in the first-born neonate group. Maternal exposures to higher temperatures during pregnancy may increase the risk of PTB, and lower temperatures may decrease the risk of PTB. Stronger effects of temperature exposures during the first trimester on PTB risk were found among the second-born neonates than among the first-born neonates.

Association of adverse birth outcomes with prenatal uranium exposure: A population-based cohort study

Uranium (U) is a well-recognized hazardous heavy metal with embryotoxicity and fetotoxicity. However, little is known about its association with adverse birth outcomes. We aimed to investigate the potential correlation between prenatal U exposure and birth outcomes. Urine samples of 8500 women were collected before delivery from a birth cohort in Wuhan, China. Concentrations of urinary U and other metals were measured by inductively coupled plasma mass spectrometry. We used multivariable logistic regressions to evaluate the associations between urinary U concentrations and adverse birth outcomes, such as preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA). Associations of urinary U concentrations with gestational age, birth weight, and birth length were investigated by linear regressions. The geometric mean of U concentration was 0.03 μg/L. After adjustment for potential confounders, we found each Log₂-unit increase in U concentration was associated with a significant decrease in gestational age [adjusted β = -0.32 day; 95% confidence interval (CI): -0.44, -0.20] and a significant increased likelihood of PTB (adjusted OR = 1.18, 95% CI: 1.07, 1.29). This birth cohort uncovered an association of maternal exposure to U during pregnancy with decreased gestational age and increased risk of PTB. Our findings reveal an association of maternal exposure to U during pregnancy with decreased gestational age and increased risk of PTB.

Blood Lead Levels in U.S. Women of Childbearing Age, 1976-2016

BACKGROUND

Lead can adversely affect maternal and child health across a wide range of exposures; developing fetuses and breastfeeding infants may be particularly vulnerable. We describe the distribution of blood lead levels (BLLs) in U.S. women of childbearing age and associations with sociodemographic, reproductive, smoking, and housing characteristics over a 40-y period.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) II, NHANES III Phase I and Phase II, and 1999-2016 continuous NHANES were used to describe the distribution of BLLs (given in micrograms per deciliter; 1μg/dL=0.0483μmol/L) in U.S. women 15-49 years of age between 1976 and 2016. For all women with valid BLLs (n=22,408), geometric mean (GM) BLLs and estimated prevalence of BLLs ≥5μg/dL were calculated overall and by selected demographic characteristics. For NHANES II, estimated prevalence of BLLs ≥10 and ≥20μg/dL were also calculated.

RESULTS

The most recent GM BLLs (2007-2010 and 2011-2016, respectively) were 0.81μg/dL [95% confidence interval (CI): 0.79, 0.84] and 0.61μg/dL (95% CI: 0.59, 0.64). In comparison, GM BLLs in earlier periods (1976-1980, 1988-1991, and 1991-1994) were 10.37μg/dL (95% CI: 9.95, 10.79), 1.85μg/dL (95% CI: 1.75, 1.94), and 1.53μg/dL (95% CI: 1.45, 1.60), respectively. In 2011-2016, 0.7% of women of childbearing age had BLLs ≥5μg/dL, and higher BLLs were associated with older age, other race/ethnicity, birthplace outside the United States, four or more live births, exposure to secondhand tobacco smoke, and ever pregnant or not currently pregnant.

DISCUSSION

Lead exposure in U.S. women of childbearing age is generally low and has substantially decreased over this 40-y period. However, based on these estimates, there are still at least 500,000 U.S. women being exposed to lead at levels that may harm developing fetuses or breastfeeding infants. Identifying high-risk women who are or intend to become pregnant remains an important public health issue. https://doi.org/10.1289/EHP5925.

Blood Lead Levels in U.S. Women of Childbearing Age, 1976-2016

BACKGROUND

Lead can adversely affect maternal and child health across a wide range of exposures; developing fetuses and breastfeeding infants may be particularly vulnerable. We describe the distribution of blood lead levels (BLLs) in U.S. women of childbearing age and associations with sociodemographic, reproductive, smoking, and housing characteristics over a 40-y period.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) II, NHANES III Phase I and Phase II, and 1999-2016 continuous NHANES were used to describe the distribution of BLLs (given in micrograms per deciliter; 1μg/dL=0.0483μmol/L) in U.S. women 15-49 years of age between 1976 and 2016. For all women with valid BLLs (n=22,408), geometric mean (GM) BLLs and estimated prevalence of BLLs ≥5μg/dL were calculated overall and by selected demographic characteristics. For NHANES II, estimated prevalence of BLLs ≥10 and ≥20μg/dL were also calculated.

RESULTS

The most recent GM BLLs (2007-2010 and 2011-2016, respectively) were 0.81μg/dL [95% confidence interval (CI): 0.79, 0.84] and 0.61μg/dL (95% CI: 0.59, 0.64). In comparison, GM BLLs in earlier periods (1976-1980, 1988-1991, and 1991-1994) were 10.37μg/dL (95% CI: 9.95, 10.79), 1.85μg/dL (95% CI: 1.75, 1.94), and 1.53μg/dL (95% CI: 1.45, 1.60), respectively. In 2011-2016, 0.7% of women of childbearing age had BLLs ≥5μg/dL, and higher BLLs were associated with older age, other race/ethnicity, birthplace outside the United States, four or more live births, exposure to secondhand tobacco smoke, and ever pregnant or not currently pregnant.

DISCUSSION

Lead exposure in U.S. women of childbearing age is generally low and has substantially decreased over this 40-y period. However, based on these estimates, there are still at least 500,000 U.S. women being exposed to lead at levels that may harm developing fetuses or breastfeeding infants. Identifying high-risk women who are or intend to become pregnant remains an important public health issue. https://doi.org/10.1289/EHP5925.

Manganese is associated with increased plasma interleukin-1β during pregnancy, within a mixtures analysis framework of urinary trace metals

Exposure to trace metals may impact reproductive health outcomes through perturbations in maternal immune signaling molecules. We conducted a cross-sectional study of 390 pregnant women from the LIFECODES birth cohort and investigated the associations between 17 urinary metals and five immune biomarkers measured in the 3rd trimester (median 26 weeks gestation). We used linear regression to estimate pair-wise associations and applied elastic net and Bayesian kernel machine regression to identify important contributing exposures analytes as well as non-linear effects. Maternal urinary manganese, nickel, and barium were positively associated with maternal plasma interleukin-1β (IL-1β). Elastic net and Bayesian kernel machine regression identified manganese as the dominant trace metal in association with IL-1β. An interquartile range difference in manganese (0.6 μg/L) was associated with a 29 % increase in IL-1β (95 % CI: 12.4-48.2). In conclusion, trace metal exposures were associated with biomarkers of immune perturbations, and this warrants further investigation.

Children's environmental health based on birth cohort studies of Asia (2) - air pollution, pesticides, and heavy metals

The life style and child raising environment in Asia are quite different compared with Western countries. Besides, the children's environmental threats and difficulties in conducting studies could be different. To address children's environmental health in Asia area, the Birth Cohort Consortium of Asia (BiCCA) was co-established in 2011. We reviewed the mercury, polychlorinated biphenyls, perfluoroalkyl substances, phthalates, and environmental tobacco smoke in pervious based on birth cohort studies in Asia. The aim of this study was to summarize the traditional environmental pollution and the target subjects were also based on the birth cohort in Asia area. Environmental pollutants included air pollutants, pesticides focusing on organochlorine pesticides, diakylphosphates, and pyrethroid, and heavy metals including lead, arsenic, cadmium, manganese, vanadium, and thallium. Fetal growth and pregnancy outcomes, childhood growth and obesity, neurodevelopment and behavioral problems, and allergic disease and immune function were classified to elucidate the children's health effects. In total, 106 studies were selected in this study. The evidences showed air pollution or pesticides may affect growth during infancy or childhood, and associated with neurodevelopmental or behavioral problems. Prenatal exposure to lead or manganese was associated with neurodevelopmental or behavioral problems, while exposure to arsenic or cadmium may influence fetal growth. In addition to the harmonization and international collaboration of birth cohorts in Asia; however, understand the whole picture of exposure scenario and consider more discipline in the research are necessary.

Maternal Heavy Metal Exposure, Thyroid Hormones, and Birth Outcomes: A Prospective Cohort Study

CONTEXT

Maternal thyroid hormones during pregnancy play a critical role in fetal development. However, whether maternal heavy metal exposure affects their thyroid hormones and the effects on fetal growth are still unclear.

OBJECTIVE

To explore the effect of heavy metal exposure on maternal thyroid hormones and the potential mediation role of thyroid hormones on birth outcomes.

METHODS

Concentrations of heavy metals in urine samples and thyroid hormones in blood samples of 675 pregnant women were measured during early pregnancy in a cohort study conducted in China. Multivariable linear regressions were applied to explore the associations of maternal urinary heavy metal levels with both maternal thyroid hormones and birth outcomes. Mediation analyses were performed to assess the mediation role of thyroid hormones in these associations.

RESULTS

Maternal urinary vanadium (V) exhibited an inverse association with free T3 (FT3) and FT3/free T4 (FT4) ratio levels. Urinary arsenic (As) and lead (Pb) had inverse relationships with FT3. We also observed the positive associations of maternal FT3 and FT3/FT4 ratio with birthweight. The mediation analyses suggested that 5.33% to 30.57% of the associations among V, As, and Pb levels and birth size might be mediated by maternal FT3 or FT3/FT4 ratio.

CONCLUSIONS

We have shown that maternal exposures to V, As, and Pb at early pregnancy were associated with decreased maternal FT3 or FT3/FT4 ratio, which might contribute to reduced birthweight. Mediation analyses indicated that maternal thyroid hormone was a possible mediator of the association between urinary heavy metals and birth size.

Toxicological effects in children exposed to lead: A cross-sectional study at the Colombian Caribbean coast

Lead (Pb) is an environmental pollutant with a toxicity that is a serious public health problem. The aim of this research was to evaluate the associations between Pb exposure and morphometric, hematological and biochemical parameters, mRNA expression of the P53, SOD1, ALAD, TNF and INF-γ genes, ALAD polymorphisms (db SNP ID: rs1800435) and Intelligence Quotient (IQ) in children from the Colombian Caribbean. Blood lead levels (BLL) were determined in 554 participants between the ages of 5-16 years old, from different places of the Colombian Caribbean. A health survey was given to assess risk factors. Whole blood was used for hematology and plasma employed to analyze markers of hepatic toxicity. Gene expression was quantified from blood mRNA by RT-PCR. The ALAD polymorphism was characterized by PCR-RFLP, and the Kaufman's brief intelligence test was employed to estimate the IQ. The mean BLL was 3.5 ± 0.2 μg/dL. The site of greatest exposure to Pb was Tasajera, a poor fishing community, with an average of 8.9 ± 0.8 μg/dL. Breastfeeding was associated with high BLL. Morphometric characteristics and IQ were negatively correlated with BLL. The blood platelet count and the mean corpuscular hemoglobin concentration showed positive and negative correlations with BLL, respectively. Negative relationships with BLL were observed with the ratios Neutrophils/Eosinophils and Neutrophils/Basophils, whereas for BLL and Neutrophils/Monocytes the association was positive. The associations between morphometric and some hematological parameters with BLL were age- and gender-related. The expression of ALAD, SOD1, INF-γ and P53 mRNA was down-regulated according to the BLL, whereas TNF showed an opposite trend. In short, fishing communities are at a high risk of Pb exposure. This xenobiotic can affect physical development and IQ, as well as hematological parameters, even at low concentrations. In addition, it can regulate the transcription of genes associated with inflammation, apoptosis, cell cycle, heme synthesis, and oxidative stress.

Assessment of heavy metals (total chromium, lead, and manganese) contamination of residential soil and homegrown vegetables near a former chemical manufacturing facility in Tarnaveni, Romania

Our aim was to assess local population exposure to heavy metals resulting from soil and vegetable contamination in Tarnaveni, Romania, an area located near a former chemical factory. We collected residential soil and vegetable samples from Tarnaveni and measured chromium (Cr), lead (Pb), and manganese (Mn) levels by atomic absorption spectrometry. We evaluated the relationship between soil and vegetable metals and the distance from the shuttered chemical factory, and calculated the hazard index to assess local population metal exposure via contaminated vegetable ingestion. Soil metal concentrations ranged between 15.6 and 525.8 mg/kg for total Cr, between 25.4 and 559.5 mg/kg for Pb, and between 363.1 and 1389.6 mg/kg for Mn. We found average concentrations of 17.8 mg/kg for total Cr, 2.2 mg/kg for Pb, and 116.6 mg/kg for Mn in local vegetables. We found soil concentrations for all three metals that exceeded normal background levels according to Romanian regulations (Pb exceeded 100 mg/kg in some of the samples), as well as measurable concentrations of metals in all analyzed vegetable samples. These preliminary data underscore a need for a more extensive investigation into associated adverse health effects in the exposed population.

Urinary trace metals individually and in mixtures in association with preterm birth

One in ten infants born in the United States is born preterm, or prior to 37 weeks gestation. Exposure to elevated levels of metals, such as lead and arsenic, has been linked to higher risk of preterm birth (PTB), but consequences of lower levels of exposure and less studied metals are unclear. We examined the associations between 17 urinary trace metals individually and in mixtures in relation to PTB. The LIFECODES birth cohort enrolled pregnant women at <15 weeks gestation at Brigham and Women's Hospital in Boston. We selected cases of PTB (n = 99) and unmatched controls (n = 291) and analyzed urine samples for a panel of trace metals (median: 26 weeks gestation). We used logistic regression models to calculate the odds ratio (OR) for PTB and subtypes of PTB based on presentation at delivery. Subtypes included spontaneous and placental PTB. We used elastic net (ENET) regularization to identify individual metals or pairwise interactions that had the strongest associations with PTB, and principal components analysis (PCA) to identify classes of exposures associated with the outcome. We observed increased odds of PTB (OR: 1.41, 95% Confidence Interval [CI]: 1.12, 1.78) in association with an interquartile range difference in urinary copper (Cu). We also observed an increased OR for selenium (OR: 1.33, 95% CI: 0.98, 1.81). ENET selected Cu as the most important trace metal associated with PTB. PCA identified 3 principal components (PCs) that roughly reflected exposure to toxic metals, essential metals, and metals with seafood as a common source of exposure. PCs reflecting essential metals were associated with increased odds of overall and spontaneous PTB. Maternal urinary copper in the third trimester was associated with increased risk of PTB, and statistical analyses for mixtures indicated that after accounting for correlation this metal was the most important statistical predictor of the outcome.

Impact of maternal thyroid autoantibodies positivity on the risk of early term birth: Ma'anshan Birth Cohort Study

PURPOSE

We aim to investigate associations of maternal serum anti-thyroperoxidase autoantibody (TPOAb) with duration of gestation. We aim to investigate whether maternal TPOAb positivity is associated with the risk of premature or early term birth.

METHODS

This was a prospective birth cohort study performed in an iodine sufficient area of China. Serum samples were collected from 2931 women at both the first and second trimesters of pregnancy. Thyrotropin (TSH), free thyroxine (FT4), and TPOAb levels were measured. Data on gestational age at birth was obtained from delivery records.

RESULTS

The prevalence of early term birth was 23.8%, while the prevalence of premature birth was 4.2%. The prevalence of TPOAb positivity was 12.1% in the first trimester and was 7.2% in the second trimester. Gestational age at birth was inversely associated with lgTPOAb both in the first trimester (β, -0.283, 95% CI -0.408, -0.158; P < 0.001) and in the second trimester (β, -0.174, 95% CI -0.319, -0.030; P = 0.018), after adjustment for potential confounding factors. There was a positive association of TPOAb positivity with the risk of early term birth both in the first (OR = 1.691, 95% CI 1.302, 2.197) and second trimesters (OR = 1.644, 95% CI 1.193, 2.264), after adjustment for potential confounding factors. TPOAb positivity in the second trimester was associated with a 1.863-fold higher risk of premature birth (OR = 1.863, 95% CI 1.009, 3.441), after adjustment for potential confounding factors.

CONCLUSIONS

Our results show that TPOAb is associated with shorter duration of gestation and with higher risk of premature and early term birth.