Early pregnancy blood lead and spontaneous abortion

Effects of hazardous chemicals on secondary sex ratio: A comprehensive review

The secondary sex ratio (SSR), defined as the ratio of male to female offspring at birth, has garnered significant scientific interest due to its potential impact on population dynamics and evolution. In recent years, there has been a growing concern regarding the potential consequences of environmental chemicals on the SSR, given their widespread exposure and potential enduring ramifications on the reproductive system. While SSR serves as an indicator of health, ongoing research and scientific inquiry are being conducted to explore the potential relationship between chemicals and offspring ratio. Although some studies have suggested a possible correlation, others have yielded inconclusive results, indicating that the topic is intricate and still needs to be elucidated. The precise mechanism by which chemical agents exert their influence on the SSR remains ambiguous, with disruption of the endocrine system being a prominent justification. In light of the complex interplay between chemical exposure and SSR, the present review aims to comprehensively examine and synthesize existing scientific literature to gain a deeper understanding of how specific chemical exposures may impact SSR. Insights into chemical hazards that shift SSR patterns or trends could guide prevention strategies, including legislative bans of certain chemicals, to minimize environmental and public health risks.

Exposure of Reproductive-Aged Women to Multiple Metals and Its Associations with Unexplained Recurrent Miscarriage

Exposure to heavy metals exerts toxic effects on female reproduction and embryo development. This study examined the exposure of patients with unexplained recurrent miscarriage (uRM) to multiple metals and the correlations among exposures to different metals. A total of 275 participants were enrolled, including 43 healthy women without previous miscarriage (the control group) and 232 uRM women (the case group); among these uRM women, 159 had two miscarriages (2M), 42 had three miscarriages (3M) and 31 had four or more miscarriages (≥4M). A total of 22 elements were measured in serum samples via inductively coupled plasma-mass spectrometry. The levels of calcium (104.37 mg/L vs. 92.65/93.02/92.61/92.47 mg/L) and selenium (131.85 µg/L vs. 117.80/118.04/115.88/124.35 µg/L) were higher in the controls than in the total uRM group and the 2M, 3M and ≥4M subgroups. The level of vanadium was significantly lower in the controls than in the total uRM group (0.15 µg/L vs. 0.23 µg/L), and the level of lead was lower in the controls than that in the total uRM group and the 2M, 3M and ≥4M subgroups (0.01 µg/L vs. 0.28/0.18/0.63/0.34 µg/L). After adjusting for age, body mass index and education level, calcium and selenium exposure were consistently negatively associated with miscarriage, while lead exposure was positively associated with miscarriage. In addition, the correlations among exposures to different metals slightly differed between the control and uRM groups. Therefore, changes in some metal elements in the blood might be related to the risk of uRM.

Association between female circulating heavy metal concentration and abortion: a systematic review and meta-analysis

Objective

This study aimed to evaluate the association between blood heavy metal (zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd)) concentrations and spontaneous abortion (SA) and recurrent pregnancy loss (RPL) and explore the possible endocrine dysfunction associated with it.

Methods

A literature search was performed in the PubMed, Embase, Cochrane Library, and Web of Science databases up to April 2023. The overall effects were expressed as the standard mean difference (SMD). Subgroup analysis was performed according to the type of abortion (SA or RPL). Stata 16.0 was utilized for data analysis.

Results

Based on the integrated findings, abortion women showed significantly lower Zn (SMD = -1.05, 95% CI: -1.74 to -0.36, p = 0.003) and Cu concentrations (SMD = -1.42, 95% CI: -1.97 to -0.87, p <0.001) and higher Pb (SMD = 1.47, 95% CI: 0.89-2.05, p <0.001) and Cd concentrations (SMD = 1.15, 95% CI: 0.45-1.85, p = 0.001) than normal pregnant women. Subgroup analysis showed that Zn and Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with RPL, whereas Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with SA.

Conclusion

Zn and Cu deficiencies and Pb and Cd exposure were associated with abortion. Endocrine dysfunction, such as insulin resistance, vitamin D insufficiency, and abnormal thyroid and sex hormone concentrations, is thought to be involved in heavy metal-related abortion.

Systemic review of genetic and epigenetic factors underlying differential toxicity to environmental lead (Pb) exposure

Lead (Pb) poisoning is a major public health concern in environmental justice communities of the USA and in many developing countries. There is no identified safety threshold for lead in blood, as low-level Pb exposures can lead to severe toxicity in highly susceptible individuals and late onset of diseases from early-life exposure. However, identifying "susceptibility genes" or "early exposure biomarkers" remains challenging in human populations. There is a considerable variation in susceptibility to harmful effects from Pb exposure in the general population, likely due to the complex interplay of genetic and/or epigenetic factors. This systematic review summarizes current state of knowledge on the role of genetic and epigenetic factors in determining individual susceptibility in response to environmental Pb exposure in humans and rodents. Although a number of common genetic and epigenetic factors have been identified, the reviewed studies, which link these factors to various adverse health outcomes following Pb exposure, have provided somewhat inconsistent evidence of main health effects. Acknowledging the compelling need for new approaches could guide us to better characterize individual responses, predict potential adverse outcomes, and identify accurate and usable biomarkers for Pb exposure to improve mitigation therapies to reduce future adverse health outcomes of Pb exposure.

Occupational Factors Affecting Women Workers’ Sexual and Reproductive Health Outcomes in Oil, Gas, and Mining Industry: A Scoping Review

Objectives: Globally, female workers workforce in Oil, Gas, and Mining (OGM) industry have increased significantly. The complexities of the OGM operations and the extensive exposure to workplace hazards potentially affect the health status of workers, including sexual and reproductive health (SRH) outcomes of female workers. Yet, the current state of knowledge on SRH issues in OGM contexts seems to be limited and fragmented. This scoping review aims to identify the occupational factors that influence women’s SRH outcomes in OGM industry.

Methods: This scoping review followed the Joanna Briggs Institute’s guidelines (PRISMA) and was conducted in five databases, including the citation chaining via Google Scholar and manual search through relevant organisations and Government websites. Sixteen articles met the inclusion criteria and were analysed.

Results: Despite the scarcity of evidence, chemical and physical are found to be the predominant factors greatly influencing women workers’ SRH outcomes in OGM. Most studies showed menstrual and cycle disorders, and risky pregnancy as key SRH issues. However, menstruation disorder was considerably linked with psychological and organisational factors.

Conclusion: This review suggests further empirical research on the relationship between OGM occupational hazards and women workers’ SRH. This will contribute to improvements in workplace safety legislations, measures, policies, and management systems taking into account women’s needs.

Effects of maternal exposure to lead on secondary sex ratio in Japan: The Japan Environment and Children's Study

A decline in the proportion of male births (secondary sex ratio, SSR) has been seen in several countries including Japan in recent years. Although previous studies have reported that the SSR is affected by exposure to chemical substances such as dioxins and polychlorinated biphenyls, as well as heavy metals such as methylmercury, the effects of lead exposure on the SSR have been little studied. The aim of this study was to determine the association between maternal lead exposure and SSR. In a large-scale nationwide birth cohort study, maternal blood lead level (BLL) was determined using whole blood from the second or third trimester of pregnancy. The association between SSR and maternal BLL was estimated using multivariable logistic models. Binomial distribution was applied to examine the differences in SSR by dividing the participants into five groups based on BLL. The primary outcome was SSR, and the child sex was obtained from the medical record transcripts. Of 104,062 fetal records, 85,171 were examined for analysis. The median maternal BLL was 5.85 ng/g (5th-95th percentile 3.45-10.6 ng/g). The overall proportion of males among participating infants was 0.512. In logistic regression models adjusted for covariates, the analysis revealed an increased odds ratio for SSR with higher blood lead concentrations [Group 2: adjusted OR 1.082, 95% confidence interval 1.037 to 1.129, Group 3: 1.122, 1.074 to 1.171, Group 4: 1.214, 1.163 to 1.268, Group 5: 1.279, 1.224 to 1.336]. Compared to the general birth probability in Japan, the group with low BLL had a lower SSR and the group with high BLL had a higher SSR. Higher maternal lead exposures during pregnancy were associated with increased SSR. Further investigations including assessment of paternal lead exposure are necessary to understand the association between lead exposure and SSR.

Parental Lead Exposure Promotes Neurobehavioral Disorders and Hepatic Dysfunction in Mouse Offspring

Lead (Pb) induces neurotoxicity in both children and adults. Children are more vulnerable to Pb toxicity than adults. Little is known about the effects of Pb on the mental health of the children who are prenatally exposed. Therefore, we designed an animal experiment to compare the adverse effects of Pb on neurobehavioral and hepatic functions between Pb-exposed (Pb mice) and parental Pb-exposed (P-Pb mice) group mice. Mice were treated with Pb-acetate (10 mg/kg bodyweight/day) via drinking water. Male mice from unexposed parents treated with Pb for 90 days were defined as Pb mice, whereas male mice from Pb-exposed parents treated with Pb for further 90 days were defined as P-Pb mice. Anxiety-like behavior and spatial memory and learning were assessed by elevated plus maze and Morris water maze. Serum hepatic enzyme activities and butyrylcholinesterase activity were measured by an analyzer. P-Pb mice displayed increased anxiety-like behavior and memory and learning impairments compared to Pb mice. BChE activity was significantly decreased in P-Pb mice compared to Pb mice. Pb levels in the brains of P-Pb mice were significantly higher than those of Pb mice. The activities of serum hepatic enzymes of P-Pb mice were also higher than those of Pb mice. Additionally, histopathology data revealed that hepatic tissue injury was more pronounced in P-Pb mice than in Pb mice. Thus, the results suggest that persistent exposure to Pb from fetus to adult causes more severe neurobehavioral changes and hepatic toxicities than adult exposure only.

Are there excess fetal deaths attributable to waterborne lead exposure during the Flint Water Crisis? Evidence from bio-kinetic model predictions and Vital Records

BACKGROUND

Flint, Michigan had elevated water lead (Pb) levels during the 2014-15 Flint Water Crisis (FWC) and reports claim the exposures caused excess fetal deaths.

OBJECTIVE

To model the likelihood of excess fetal deaths occurring from FWC lead exposure and compare results to Vital Records.

METHODS

We used an established bio-kinetic model to predict relative blood lead trends in pregnant women from characteristic exposure to 90th percentile water lead levels (WLLs), and another established model to then estimate characteristic miscarriage (<20 gestation weeks) odds ratios (OR) in Flint (2011-17). For comparison, we made similar predictions for exposures during (1) Washington DC's worst water lead crisis year (2001), (2) Flint "Resident Zero" home with anomalously high WLLs, and (3) 19th century lead-based abortifacients. Data on stillbirths (≥20 gestation weeks) and total fertility rates were obtained from the State of Michigan.

RESULTS

The models predicted that pregnant women drinking water with representative 90th percentile WLLs had a miscarriage OR during the worst FWC period (June-August 2014) of 1.21 (95% CI = 1.02,1.60), versus 1.66 (95% CI = 1.07, 3.56) during a time of high water lead 3 years before the FWC and 1.00 (95% CI = 1.00, 1.01) post-FWC. The corresponding predicted OR in late-2001 for Washington D.C. when higher fetal death rates were statistically associated with very high WLLs was 3.01 (95% CI = 1.16, 16.23). No apparent differences were revealed in overall and race-specific stillbirth rates before, during, or after the FWC. Total fertility rates dropped 6.8% during the FWC (April 2014-October 2015 versus April 2012-October 2013), but this is now revealed to be within the normal annual variation (-9.4% to +15%) observed post-FWC when residents were protected from water lead exposure.

SIGNIFICANCE

Neither model simulations nor Vital Records data are consistent with the hypothesis that there was an uptick in fetal deaths or decreased fertility attributable to water lead exposure during the FWC.

Umbilical Cord Blood Lead Level Disparities between Flint and Detroit

OBJECTIVE

The lead-in-water impact of the Flint water crisis on the youngest and most neurodevelopmentally vulnerable population was largely unknown. The objective of this study was to investigate and compare cord blood lead levels (CBLLs) in newborns in Flint, Michigan, after the Flint water crisis, to a group of Detroit newborns.

STUDY DESIGN

Mothers of 99 Flint newborns were surveyed about potential lead exposures. These neonates were born after the recognition of population-wide lead-in-water contamination. CBLLs were measured and maternal-fetal metrics were reviewed. CBLLs and maternal-fetal metrics were then compared with those of a retrospective cohort of 116 Detroit newborns who previously shared the same water source. Analysis involved descriptive statistics, independent t-test, and χ ² analysis.

RESULTS

CBLLs greater than or equal to 1 μg/dL (0.05 μmol/L) were more prevalent among Flint newborns (14%), as compared with Detroit newborns (2%; p = 0.001). This was a sevenfold disparity between Flint and Detroit newborns. No statistically significant differences were found in birth weight, head circumference, small for gestational age status, gestational age, or preterm status among the two groups.

CONCLUSION

The Flint water crisis potentially exposed newborns to lead in utero, implicating maternal-fetal outcomes and future health and development. Primary prevention efforts, including identification and mitigation of lead exposure before conception and during pregnancy, are needed. New environmental exposure detection methods and long-term neurodevelopmental follow-up will complement the findings of this study.

Prenatal blood levels of some toxic metals and the risk of spontaneous abortion

High-level toxic metal exposure has become rare in the recent years. Although, it has not known whether relatively lower exposure may adversely affect human reproductive system. Spontaneous abortion (SA) is a serious reproductive problem, which, in many cases, the cause(s) is not clearly understood. To assess the relationship between prenatal blood level of metals and SA risk, we compared blood concentration of some heavy metals in samples taken from mothers recruited in Tehran Environment and Neurodevelopmental Defects (TEND) study conducted on apparently healthy pregnant women in Tehran, Iran who subsequently experienced spontaneous abortion with mothers who their pregnancy ended to live births. During early gestation, 206 women were enrolled to the survey and followed up till fetal abortion or baby deliveries occur. Blood metal concentrations were measured using an inductively coupled plasma mass spectrometer. The mean blood levels of lead, antimony, and nickel were higher in SA than ongoing pregnancy; however, this difference was not statistically significant. When adjusted for covariates, the logistic regression analysis showed significant association between maternal age and the risk of SA in all models. Among toxic metals only antimony had a noticeable positive relation with the risk of SA (OR: 1.65, 95% CI:1.08-2.52, P value: 0.02). Pearson's correlation coefficient showed significant (P < 0.05) positive correlations among prenatal blood metals levels, except for nickel. Although the present study failed to provide strong evidence for the effects of toxic metals on the occurrence of SA at the relatively low-levels, these metals should be avoided in women who plan pregnancy and/or during the early stages of gestation to prevent the chance of adverse effects.

Blood lead level monitoring related to environmental exposure in the general Iranian population: a systematic review and meta-analysis

Exposure to lead can cause adverse health problems incorporating hypophosphatemia, heart and liver disease, cancers, neurological and cardiovascular diseases, central nervous disorders, and sensory disorders. This study investigated the blood lead level in the general Iranian population with environmental exposure to lead. In the presented systematic review and meta-analysis, the authors searched Iranian dataset, including Magiran, SID, Iranmedex, and Nopa, and the main dataset, comprising PubMed, Scopus, Embase, and Web of Science, all available articles until 12 January 2019, and extracting 55 studies (with 63 data for analysis) to a meta-analysis. A comprehensive meta-analysis software, pooled standard deviation, mean, sample size, and the utterly random effects model was analyzed in this study. The results showed that the overall mean BLL (95% CI) in total inquiries was 6.41 μg/dL (5.96 to 6.87). Besides, the results for gender and age subgroups were as follows: mean BLL, 6.47 μg/dL, 95% CI, 5.79, to 7.15, mean BLL, 6.44 μg/dL, 95% CI, 5.96, to 6.91, respectively. Conclusively the mean BLL in the Iranian population was higher than the recommended level by the US Centers for Disease Control and Prevention (CDC). Results indicated that the mean BLL in men and adults was more elevated than in women and children, respectively. Therefore, BLL monitoring and screening of the general Iranian population are is necessary to determine a reference value.

The Impact of the Flint Water Crisis on Fertility

Flint switched its public water source in April 2014, increasing exposure to lead and other contaminants. We compare the change in the fertility rate and in health at birth in Flint before and after the water switch to the changes in other cities in Michigan. We find that Flint fertility rates decreased by 12 % and that overall health at birth decreased. This effect on health at birth is a function of two countervailing mechanisms: (1) negative selection of less healthy embryos and fetuses not surviving (raising the average health of survivors), and (2) those who survived being scarred (decreasing average health). We untangle this to find a net of selection scarring effect of 5.4 % decrease in birth weight. Because of long-term effects of in utero exposure, these effects are likely lower bounds on the overall effects of this exposure.

Blood Lead Levels in Females of Childbearing Age in Flint, Michigan, and the Water Crisis

OBJECTIVE

To compare blood lead levels in females of childbearing age, 12-50 years, living within and adjacent to Flint, Michigan, before, during, and after the Flint River water exposure and compare the levels to those that have been shown to cause fetal loss and preterm birth.

METHODS

The switch in the community water source to the Flint River occurred on April 25, 2014, and was reverted to the original source on October 15, 2015. Using a retrospective cross-sectional study design using geocoded blood lead levels obtained from all females of childbearing age available from a single hospital database, we compared blood lead levels for the following 18-month time periods: April 25, 2012-October 15, 2013 (PRE), April 25, 2014-October 15, 2015 (DURING), and April 25, 2016-October 15, 2017 (POST).

RESULTS

Results are reported as geometric mean (95% CI). Within Flint, PRE blood lead levels in females of childbearing age were 0.69 micrograms/dL (95% CI 0.63-0.75), DURING blood lead levels were 0.65 micrograms/dL (95% CI 0.60-0.71), and POST blood lead levels were 0.55 micrograms/dL (95% CI 0.54-0.56). DURING Flint River water exposure blood lead levels were not significantly different than the PRE Flint River water time period. POST Flint River water exposure blood lead levels were significantly lower than both PRE and DURING levels. Overall, lower blood lead levels were found outside the Flint boundary in all cohorts.

CONCLUSION

Blood lead levels in Flint females of childbearing age did not increase during the Flint River water exposure and subsequent 18-month time period. Mean blood lead levels during the Flint River water exposure are not consistent with the markedly higher blood lead levels reported in the literature to be associated with fetal loss, low birth weight, or preterm birth.

Environmental & occupational exposure & female reproductive dysfunction

All individuals are exposed to certain chemical, physical, biological, environmental as well as occupational factors. The data pertaining to role of these factors on female reproduction are scanty as compared to male. The available data suggest the adverse effects of certain toxicants, viz., metals such as lead, cadmium and mercury, pesticides such as bis(4-chlorophenyl)-1,1,1-trichloroethane and organic solvent such as benzene, toluene and ionizing radiation on the female reproductive system affecting directly the organ system or impacting in directly through hormonal impairments, molecular alterations, oxidative stress and DNA methylation impairing fertility as well as pregnancy and its outcomes. Thus, there is a need for awareness and prevention programme about the adverse effects of these factors and deterioration of female reproductive health, pregnancy outcome and offspring development as some of these chemicals might affect the developing foetus at very low doses by endocrine disruptive mechanism.

Change of the levels of trace elements and heavy metals in threatened abortion

BACKROUND

This study aimed to investigate the impact of changes in the serum levels of trace elements and heavy metals in threatened abortion, which is a common complication in early pregnancy. Earlier studies have shown that changes in the serum levels of some trace elements and increased serum concentrations of heavy metals are associated with spontaneous abortion; however, this relationship has not been fully clarified.

METHODS

The patient group consisted of 45 pregnant women diagnosed with threatened abortion. There were 40 healthy nonpregnant women in the control group. Blood samples were obtained from the patients and the healthy controls, and the concentrations of serum trace elements and heavy metals were measured using atomic absorption spectrophotometry.

RESULTS

Statistically significant decreases were found in the serum zinc (Zn), iron (Fe), magnesium (Mg) and manganese (Mn) levels, and significant increases were found in the serum copper (Cu), cadmium (Cd) and lead (Pb) levels in cases of threatened abortion in comparison to the controls (p < 0.001). However, there was no difference between the groups in terms of the serum cobalt (Co) levels (p > 0.001).

CONCLUSION

Changes in the balance of some essential trace elements (especially decreases in Fe and Zn) and elevated concentrations of some toxic heavy metals in the blood may be important diagnostic and prognostic parameters for threatened abortion.

Maternal lead exposure and risk of congenital heart defects occurrence in offspring

Maternal lead exposure may be harmful to fetal development. However, sufficient evidence was lacked about the risk on cardiac development in offspring. To explore the association between maternal lead exposure and risks of congenital heart defects (CHDs) occurrence in fetuses, a case-control study was adopted during pregnant women making antenatal examinations. The maternal hair lead levels were measured by using inductively coupled plasma mass spectrometry (ICP-MS), and logistic regression analysis was used to calculate the odds ratio (OR). Three hundred and sixteen cases and 348 controls were eligible to the study. The median level of lead in maternal hair of case (0.670ng/mg) was significantly higher (AOR 3.07, 95% CI 2.00-4.72) than that of the control (0.461ng/mg), including the CHD cases with or without extracardiac malformations (AOR 3.55, 2.94, respectively). Maternal lead exposure is associated with the risk of some subtypes of CHDs occurrence in offspring. The potential dose-response relationship is also presented.