Association between maternal blood cadmium during pregnancy and birth weight and the risk of fetal growth restriction: The EDEN mother–child cohort study

Maternal serum cadmium level during pregnancy and its association with small for gestational age infants: a population-based birth cohort study

The association between maternal cadmium (Cd) exposure during pregnancy and the increased risk of fetal growth restriction (FGR) remains controversial. The present study evaluated the association between maternal serum Cd level and risk of small for gestational age (SGA) infants in a Chinese population. The present study analyzed a subsample of the C-ABCS cohort that recruited 3254 eligible mother-and-singleton-offspring pairs. Maternal serum Cd level during pregnancy was measured by graphite furnace atomic absorption spectrometry. The rate and odds ratio (OR) for SGA infant were calculated. The rate for SGA infant was 10.6% among subjects with H-Cd (≥1.06 μg/L), significantly higher than 7.5% among subjects with L-Cd (<1.06 μg/L). OR was 1.45 (95% CI: 1.11, 1.90; P = 0.007) among subjects with H-Cd. Adjusted OR for SGA infants was 1.43 (95% CI: 1.09, 1.88; P = 0.007) among subjects with H-Cd. Taken together, we observe the fact that maternal Cd exposure at middle gestational stage, elevates the risk of SGA in contrast to early gestational stage. The present results might be interesting and worth more discussing, and guarantee to further studies.

Delayed vasculogenesis and impaired angiogenesis due to altered Ang-2 and VE-cadherin levels in the chick embryo model following exposure to cadmium

PURPOSE

Cadmium (Cd) causes chick embryo malformation and abnormal extra-embryonic vasculature. This study investigates the effect of Cd on vasculogenesis, quantifies extra-embryonic vascular development following exposure to cadmium acetate (CdAc).

METHODS

After 48 or 60 h incubation, chicks were explanted and treated with 50 µl of 50 µM CdAc or equimolar sodium acetate. Embryos were again incubated then re-examined 4, 8, 24 and 48 h later. Gross morphological and histological manifestations were noted. Vasculogenesis was assessed by the development of omphalomesenteric vessels from blood islands. Sinus terminalis (ST), area vasculosa (AV), vessel density and embryo crown-rump length (CRL) were measured. Ang-2 and VE-cadherin mRNA expression was analysed by RT-PCR.

RESULTS

Vasculogenesis was delayed on gross and histological examination. ST length, AV area, vessel density and CRL were significantly reduced in the Cd group. Ang-2 was increased 4 h after exposure to Cd, whereas VE-cadherin was reduced.

CONCLUSION

Cd exposure inhibits normal development of extra-embryonic vasculature in line with growth retardation of the chick embryo in association with altered expression of Ang-2 and VE-cadherin.

Effects of Environmental Exposures on Fetal and Childhood Growth Trajectories

Delayed fetal growth and adverse birth outcomes are some of the greatest public health threats to this generation of children worldwide because these conditions are major determinants of mortality, morbidity, and disability in infancy and childhood and are also associated with diseases in adult life. A number of studies have investigated the impacts of a range of environmental conditions during pregnancy (including air pollution, endocrine disruptors, persistent organic pollutants, heavy metals) on fetal and child development. The results, while provocative, have been largely inconsistent. This review summarizes up to date epidemiologic studies linking major environmental pollutants to fetal and child development and suggested future directions for further investigation.

Maternal cadmium, iron and zinc levels, DNA methylation and birth weight

Background

Cadmium (Cd) is a ubiquitous and environmentally persistent toxic metal that has been implicated in neurotoxicity, carcinogenesis and obesity and essential metals including zinc (Zn) and iron (Fe) may alter these outcomes. However mechanisms underlying these relationships remain limited.

Methods

We examined whether maternal Cd levels during early pregnancy were associated with offspring DNA methylation at regulatory sequences of genomically imprinted genes and weight at birth, and whether Fe and Zn altered these associations. Cd, Fe and Zn were measured in maternal blood of 319 women ≤12 weeks gestation. Offspring umbilical cord blood leukocyte DNA methylation at regulatory differentially methylated regions (DMRs) of 8 imprinted genes was measured using bisulfite pyrosequencing. Regression models were used to examine the relationships among Cd, Fe, Zn, and DMR methylation and birth weight.

Results

Elevated maternal blood Cd levels were associated with lower birth weight (p = 0.03). Higher maternal blood Cd levels were also associated with lower offspring methylation at the PEG3 DMR in females (β = 0.55, se = 0.17, p = 0.05), and at the MEG3 DMR in males (β = 0.72, se = 0.3, p = 0.08), however the latter association was not statistically significant. Associations between Cd and PEG3 and PLAGL1 DNA methylation were stronger in infants born to women with low concentrations of Fe (p < 0.05).

Conclusions

Our data suggest the association between pre-natal Cd and offspring DNA methylation at regulatory sequences of imprinted genes may be sex- and gene-specific. Essential metals such as Zn may mitigate DNA methylation response to Cd exposure. Larger studies are required.

Metals exposure and risk of small-for-gestational age birth in a Canadian birth cohort: The MIREC study

BACKGROUND

Lead, mercury, cadmium and arsenic are some of the most common toxic metals to which Canadians are exposed. The effect of exposure to current low levels of toxic metals on fetal growth restriction is unknown.

OBJECTIVE

The aim of this study was to examine relationships between exposure to lead, mercury, cadmium and arsenic during pregnancy, and risk of small for gestational age (SGA) birth.

METHODS

Lead, mercury, cadmium and arsenic levels were measured in blood samples from the first and third trimesters in 1835 pregnant women from across Canada. Arsenic species in first trimester urine were also assessed. Relative risks and 95% confidence intervals were estimated using log binomial multivariate regression. Important covariates including maternal age, parity, pre-pregnancy BMI, and smoking, were considered in the analysis. An exploratory analysis was performed to examine potential effect modification of these relationships by single nucleotide polymorphisms (SNPs) in GSTP1 and GSTO1 genes.

RESULTS

No association was found between blood lead, cadmium or arsenic and risk for SGA. We observed an increased risk for SGA for the highest compared to the lowest tertile of exposure for mercury (>1.6 µg/L, RR=1.56.; 95% CI=1.04-2.58) and arsenobetaine (>2.25 µg/L, RR=1.65; 95% CI=1.10-2.47) after adjustment for the effects of parity and smoking. A statistically significant interaction was observed in the relationship between dimethylarsinic acid (DMA) levels in urinary arsenic and SGA between strata of GSTO1 A104A (p for interaction=0.02). A marginally significant interaction was observed in the relationship between blood lead and SGA between strata of GSTP1 A114V (p for interaction=0.06).

CONCLUSIONS

These results suggest a small increase in risk for SGA in infants born to women exposed to mercury and arsenic. Given the conflicting evidence in the literature this warrants further investigation in other pregnant populations.

Concentration of lead, mercury, cadmium, aluminum, arsenic and manganese in umbilical cord blood of Jamaican newborns

The objective of this study was to characterize the concentrations of lead, mercury, cadmium, aluminum, and manganese in umbilical cord blood of Jamaican newborns and to explore the possible association between concentrations of these elements and certain birth outcomes. Based on data from 100 pregnant mothers and their 100 newborns who were enrolled from Jamaica in 2011, the arithmetic mean (standard deviation) concentrations of cord blood lead, mercury, aluminum, and manganese were 0.8 (1.3 μg/dL), 4.4 (2.4 μg/L), 10.9 (9.2 μg/L), and 43.7 (17.7 μg/L), respectively. In univariable General Linear Models, the geometric mean cord blood aluminum concentration was higher for children whose mothers had completed their education up to high school compared to those whose mothers had any education beyond high school (12.2 μg/L vs. 6.4 μg/L; p < 0.01). After controlling for maternal education level and socio-economic status (through ownership of a family car), the cord blood lead concentration was significantly associated with head circumference (adjusted p < 0.01). Our results not only provide levels of arsenic and the aforementioned metals in cord blood that could serve as a reference for the Jamaican population, but also replicate previously reported significant associations between cord blood lead concentrations and head circumference at birth in other populations.

Birth outcomes and background exposures to select elements, the Longitudinal Investigation of Fertility and the Environment (LIFE)

Evidence suggests that trace exposures to select elements may increase the risk for adverse birth outcomes. To investigate further, we used multiple regression to assess associations between preconception parental exposures to Pb, Cd, and total Hg in blood, and 21 elements in urine, with n=235 singleton birth outcomes, adjusted for confounders and partner's exposure. Earlier gestational age at delivery (GA) was associated with higher tertiles of urine maternal W (-1.22 days) and paternal U (-1.07 days), but GA was later for higher tertiles of maternal (+1.11 days) and paternal (+1.30 days) blood Hg. Additional analysis indicated shorter GA associated with higher paternal urine Ba, W, and U, and with higher maternal blood Pb for boys, but GA was longer in association with higher maternal urine Cr. Birth weight (BW) was lower for higher tertiles of paternal urine Cs (-237.85g), U (-187.34g), and Zn (-209.08g), and for higher continuous Cr (P=0.021). In contrast, BW was higher for higher tertiles of paternal urine As (+194.71g) and counterintuitively for maternal blood Cd (+178.52g). Birth length (BL) was shorter for higher tertiles of urine maternal W (-1.22cm) and paternal U (-1.10cm). Yet, higher tertiles of maternal (+1.11cm) and paternal (+1.30) blood Hg were associated with longer BL. Head circumference at delivery was lower for higher tertiles of paternal urine U (-0.83cm), and for higher continuous Mo in boys (-0.57cm). Overall, associations were most consistently indicated for GA and measures of birth size with urine W and U, and paternal exposures were more frequently associated than maternal. Though limited by several factors, ours is the largest multi-element investigation of prospective couple-level trace exposures and birth outcomes to date; the novel observations for W and U merit further investigation.

Maternal blood metal levels and fetal markers of metabolic function

Exposure to metals commonly found in the environment has been hypothesized to be associated with measures of fetal growth but the epidemiological literature is limited. The Maternal-Infant Research on Environmental Chemicals (MIREC) study recruited 2001 women during the first trimester of pregnancy from 10 Canadian sites. Our objective was to assess the association between prenatal exposure to metals (lead, arsenic, cadmium, and mercury) and fetal metabolic function. Average maternal metal concentrations in 1st and 3rd trimester blood samples were used to represent prenatal metals exposure. Leptin and adiponectin were measured in 1363 cord blood samples and served as markers of fetal metabolic function. Polytomous logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between metals and both high (≥ 90%) and low (≤ 10%) fetal adiponectin and leptin levels. Leptin levels were significantly higher in female infants compared to males. A significant relationship between maternal blood cadmium and odds of high leptin was observed among males but not females in adjusted models. When adjusting for birth weight z-score, lead was associated with an increased odd of high leptin. No other significant associations were found at the top or bottom 10th percentile in either leptin or adiponectin models. This study supports the proposition that maternal levels of cadmium influence cord blood adipokine levels in a sex-dependent manner. Further investigation is required to confirm these findings and to determine how such findings at birth will translate into childhood anthropometric measures.

Maternal cadmium levels during pregnancy associated with lower birth weight in infants in a North Carolina cohort

Cadmium (Cd) is a ubiquitous environmental contaminant, a known carcinogen, and understudied as a developmental toxicant. In the present study, we examined the relationships between Cd levels during pregnancy and infant birth outcomes in a prospective pregnancy cohort in Durham, North Carolina. The study participants (n = 1027) had a mean Cd level of 0.46 µg/L with a range of <0.08 to 2.52 µg/L. Multivariable models were used to establish relationships between blood Cd tertiles and fetal growth parameters, namely birth weight, low birth weight, birth weight percentile by gestational age, small for gestational age, pre-term birth, length, and head circumference. In multivariable models, high maternal blood Cd levels (≥0.50 µg/L) during pregnancy were inversely associated with birth weight percentile by gestational age (p = 0.007) and associated with increased odds of infants being born small for gestational age (p<0.001). These observed effects were independent of cotinine-defined smoking status. The results from this study provide further evidence of health risks associated with early life exposure to Cd among a large pregnancy cohort.

Preeclampsia induced by cadmium in rats is related to abnormal local glucocorticoid synthesis in placenta

BACKGROUND

Cadmium (Cd) is a major environmental pollutant that causes multiple adverse health effects in humans and animals. In this study, we investigated Cd-mediated toxic effects in rats during pregnancy and endocrine intervention in the placenta.

METHODS

We exposed pregnant rats to intraperitoneal Cd (CdCl2) at various doses (0, 0.25, and 0.5 mg/kg BW/day) from days 5 to 19 of pregnancy and evaluated the maternal-placental-fetal parameters linked to preeclampsia. We measured the corticosterone level in rat serum and placental tissue by sensitive ELISA and also analyzed the expression of glucocorticoid synthesis enzymes in the placenta.

RESULTS

Key features of preeclampsia (PE), including hypertension, proteinuria, glomerular endotheliosis, placental abnormalities and small fetal size, appeared in pregnant rats after injection with 0.5 mg/kg BW/day Cd. The placental corticosterone production and maternal and fetal plasma corticosterone levels were increased in rats treated with 0.5 mg/kg BW/day Cd (P <0.01). The expression of 21-hydroxylase (CYP21) and 11beta-hydroxylase (CYP11B1), enzymes essential for corticosteroid synthesis, were increased in Cd-exposed placenta (P <0.01). 11beta-hydroxysteroid dehydrogenase (11beta-HSD2), a dominant negative regulator of local glucocorticoid levels, was decreased in Cd-exposed placenta (P <0.01).

CONCLUSIONS

Our study demonstrates for the first time that changes in placental glucocorticoid synthesis induced by Cd exposure during pregnancy could contribute to preeclamptic conditions in rats.

The effects of prenatal exposure to low-level cadmium, lead and selenium on birth outcomes

To evaluate the current maternal and fetal exposure to cadmium (Cd), lead (Pb) and selenium (Se), and their potential effect on newborn birth outcomes, a cross-sectional study involving an assessment of the levels of these three metals in maternal blood, urine and umbilical cord blood was conducted in 209 pregnant women living in Eastern China. The maternal blood, urine and cord blood samples were collected and measured with inductively coupled plasma mass spectrometry (ICP-MS). The maternal blood concentrations of Cd, Pb and Se (the geometric means (GMs) were 0.48, 39.50 and 143.53 μg L(-1)) were significantly higher than and correlated with those in the cord blood (GM: 0.09, 31.62 and 124.61 μg L(-1)). In the urine samples, the GMs for Cd, Pb and Se were 0.13, 0.48, and 4.78 μg L(-1), respectively. Passive smoking was found to positively correlate with urine Cd (r=0.16) and negatively correlate with urine Se (r=-0.29). The maternal blood Se level was negatively associated with the cord Cd levels (r=-0.41). The blood Cd concentration in the mother could significantly affect the newborn birth weight (r=-0.22), but it was not correlated with birth height. We identified cord Se as a new factor which significantly correlated with birth weight. In conclusion, maternal Cd, Pb, Se exposure correlated with their umbilical cord concentration, and maternal Cd exposure might affect the newborn birth weight. Increasing the Se intake might reduce the cord blood Cd concentration and promote the fetal growth.

Nongenetic determinants of age at menarche: a systematic review

BACKGROUND

The acceleration of pubertal development is an important medical and social problem, as it may result in increased morbidity and mortality in later life. This systematic review summarizes relevant data about nongenetic factors, which contribute to age at menarche (AAM), and suggests those which may be the most important.

METHODS

The available literature from 1980 till July 2013 was searched using PubMed and Google Scholar databases. Finally, 154 papers were selected for the analysis.

RESULTS

Environmental factors, which may affect AAM, vary in populations of different ethnicity. The prenatal, infancy, and early childhood periods are the most susceptible to these factors. Body weight, high animal protein intake, family stressors (e.g., single parenting), and physical activity seem to influence AAM in most populations.

CONCLUSIONS

The data about influence of nongenetic factors on AAM are still inconsistent. The factors affecting prenatal and early childhood growth seem to have a larger effect on further sexual maturation. Further studies are needed in order to validate the association between other environmental determinants and AAM in different ethnical groups.

The obesogen tributyltin

The obesogen hypothesis postulates the role of environmental chemical pollutants that disrupt homeostatic controls and adaptive mechanisms to promote adipose-dependent weight gain leading to obesity and metabolic syndrome complications. One of the most direct molecular mechanisms for coupling environmental chemical exposures to perturbed physiology invokes pollutants mimicking endogenous endocrine hormones or bioactive dietary signaling metabolites that serve as nuclear receptor ligands. The organotin pollutant tributyltin can exert toxicity through multiple mechanisms but most recently has been shown to bind, activate, and mediate RXR-PPARγ transcriptional regulation central to lipid metabolism and adipocyte biology. Data in support of long-term obesogenic effects on whole body adipose tissue are also reported. Organotins represent an important model test system for evaluating the impact and epidemiological significance of chemical insults as contributing factors for obesity and human metabolic health.

Lead, cadmium and mercury levels in pregnancy: the need for international consensus on levels of concern

For heavy metals that have any degree of transfer though the placenta to the fetus, it is unlikely that there are safe limits for maternal blood levels. The only means of reducing fetal exposure is to minimise maternal exposure. There are few recommendations for levels of concern. With the exception of US recommendations for maternal Pb levels, but there are no international levels of concern or cut-off levels specifically for pregnancy for heavy metals, so that comparisons can generally only be made with national reference values relating to similar physiological statuses or age groups. These include recommendations for Cd levels by Germany (reference value for non-smoking adults aged 18–69 years, 1 µg/l) and for Hg by Germany (reference value for adults age 18–60 years with fish intake ⩽3 times per month, 2.0 µg/l) and the USA (cut-off level for women, 5.8 µg/dl). To illustrate the lack of cohesion, we present data on blood Pb, Cd and Hg levels from pregnant women enroled in the UK Avon Longitudinal Study of Parents and Children study and compare the values with present levels of concern and recommended cut-off values. We also compare the levels with those found in other groups of pregnant women worldwide to strengthen the database for the development of levels of concern in pregnancy. The need for clarity of terminology in describing levels of concern is discussed. There is a pressing need for international consensus on levels of concern for all age groups and physiological statuses, particularly for pregnancy.

Birth outcome measures and maternal exposure to heavy metals (lead, cadmium and mercury) in Saudi Arabian population

This cross-sectional study was conducted to assess the association between exposure to heavy metals (lead, cadmium and mercury) during pregnancy and birth outcomes in 1578 women aged 16-50 years who delivered in Al-Kharj hospital, Saudi Arabia, in 2005 and 2006. The levels of lead, cadmium and mercury were measured in umbilical cord blood, maternal blood and the placenta. Outcome variables were anthropometric measures taken at birth, along with the risk of being small-for-gestational age (SGA). We selected the 10th percentile as the cutoff for dichotomizing measures of birth outcome. Cadmium, despite its partial passage through the placenta had the most prominent effect on several measures of birth outcome. After adjustment for potential confounders, logistic regression models revealed that crown-heel length (p=0.034), the Apgar 5-minute score (p=0.004), birth weight (p=0.015) and SGA (p=0.049) were influenced by cadmium in the umbilical cord blood. Significant decreases in crown-heel length (p=0.007) and placental thickness (p=0.022) were seen with higher levels of cadmium in maternal blood. As placental cadmium increased, cord length increased (p=0.012) and placental thickness decreased (p=0.032). Only lead levels in maternal blood influenced placental thickness (p=0.011). Mercury in both umbilical cord and maternal blood was marginally associated with placental thickness and placental weight, respectively. Conversely, placental mercury levels significantly influenced head circumference (p=0.017), the Apgar 5-minute score (p=0.01) and cord length (p=0.026). The predictions of these models were further assessed with the area under the curve (AUC) of the receiver operating curves (ROCs), which were modest (larger than 0.5 and smaller than 0.7). The independence of gestational age or preterm births on the observed effect of metals on some measures of birth outcome, suggested detrimental effects of exposure on fetal development. The magnitude of the estimated effects might not necessarily be of clinical significance for infants but may have a considerable public-health relevance given the high prevalence of exposure to heavy metals. Further research should be conducted to confirm these findings and to evaluate their long-term risks, if any.