Associations between socioeconomic status, psychosocial stress, and urinary levels of 8-iso-prostaglandin-F2α during pregnancy in Puerto Rico

The association between prenatal oxidative stress levels measured by isoprostanes and offspring neurodevelopmental outcomes at 36 months

Oxidative stress during pregnancy has been a mechanistic pathway implicated in autism development, yet few studies have examined this association directly. Here, we examined the association of prenatal levels of 8-iso-PGF2α, a widely used measure of oxidative stress, and several neurodevelopmental outcomes related to autism in children. Participants included 169 mother-child pairs from the Early Autism Risk Longitudinal Investigation (EARLI), which enrolled mothers who had an autistic child from a previous pregnancy and followed them through a subsequent pregnancy and until that child reached age 3 years. Maternal urine samples were collected during the second trimester of pregnancy and were later measured for levels of isoprostanes. Child neurodevelopmental assessments included the Mullen Scales of Early Learning (MSEL), the Social Responsiveness Scale (SRS), and the Vineland Adaptive Behavior Scale (VABS), and were conducted around 36 months of age. Primary analyses examined associations between interquartile range (IQR) increases in 8-iso-PGF2α levels, and total composite scores from each assessment using quantile regression. In adjusted analyses, we did not observe statistically significant associations, though estimates suggested modestly lower cognitive scores (β for MSEL = -3.68, 95% CI: -10.09, 2.70), and minor increases in autism-related trait scores (β for SRS T score = 1.68, 95% CI: -0.24, 3.60) with increasing 8-iso-PGF2α. These suggestive associations between decreased cognitive scores and increased autism-related traits with increasing prenatal oxidative stress point to the need for continued investigation in larger samples of the role of oxidative stress as a mechanistic pathway in autism and related neurodevelopmental outcomes.

Identification of novel F2-isoprostane metabolites by specific UDP-glucuronosyltransferases

UDP-glucuronosyltransferases (UGTs) catalyze the conjugation of glucuronic acid with endogenous and exogenous lipophilic small molecules to facilitate their inactivation and excretion from the body. This represents approximately 35 % of all phase II metabolic transformations. Fatty acids and their oxidized eicosanoid derivatives can be metabolized by UGTs. F2-isoprostanes (F2-IsoPs) are eicosanoids formed from the free radical oxidation of arachidonic acid. These molecules are potent vasoconstrictors and are widely used as biomarkers of endogenous oxidative damage. An increasing body of evidence demonstrates the efficacy of measuring the β-oxidation metabolites of F2-IsoPs rather than the unmetabolized F2-IsoPs to quantify oxidative damage in certain settings. Yet, the metabolism of F2-IsoPs is incompletely understood. This study sought to identify and characterize novel phase II metabolites of 15-F2t-IsoP and 5-epi-5-F2t-IsoP, two abundantly produced F2-IsoPs, in human liver microsomes (HLM). Utilizing liquid chromatography-mass spectrometry, we demonstrated that glucuronide conjugates are the major metabolites of these F2-IsoPs in HLM. Further, we showed that these molecules are metabolized by specific UGT isoforms. 15-F2t-IsoP is metabolized by UGT1A3, 1A9, and 2B7, while 5-epi-5-F2t-IsoP is metabolized by UGT1A7, 1A9, and 2B7. We identified, for the first time, the formation of intact glucuronide F2-IsoPs in human urine and showed that F2-IsoP glucuronidation is reduced in people supplemented with eicosapentaenoic and docosahexaenoic acids for 12 weeks. These studies demonstrate that endogenous F2-IsoP levels can be modified by factors other than redox mechanisms.

Adolescent endocrine disrupting chemical exposure and academic achievement

BACKGROUND

Epidemiologic studies support associations of exposure to endocrine disrupting chemicals (EDCs), such as some phthalates, phenols, and parabens with a wide range of cognitive and behavioral traits. While many of these traits are associated with academic achievement, the relationship of EDC exposure specifically with academic achievement in adolescence has not yet been studied.

OBJECTIVE

We assessed the association of urinary biomarker concentrations of EDCs with academic achievement in adolescents as well as the potential for psychosocial factors to modify associations.

METHODS

We quantified urinary concentrations of select EDCs in 205 adolescent participants from the New Bedford Cohort (NBC), a prospective birth cohort of children born to mothers residing near the New Bedford Harbor Superfund site in Massachusetts, and estimated associations between EDCs and adolescent academic achievement assessed with the Wide Range Achievement Test (WRAT). Measures of socioeconomic status and the home environment were used to estimate psychosocial stress.

RESULTS

Urinary concentrations of antiandrogenic phthalates were inversely associated with Math Computation scores. For example, each doubling of the concentration of antiandrogenic phthalate metabolites in urine was associated with a 1.94 point decrease (95% CI: 3.84, -0.05) in Math Computation scores, indicating poorer performance. For the most part, associations were stronger in adolescents with more, as compared to less, social disadvantage, but most of these differences did not achieve statistical significance.

CONCLUSION

Our findings support the potential for adolescents' exposure to antiandrogenic phthalates to correlate with poorer academic achievement in math, particularly among participants with greater psychosocial stress.

The Relationship of Preconception and Early Pregnancy Isoprostanes with Fecundability and Pregnancy Loss

BACKGROUND

Although redox stress likely plays an important role in reproductive health, the utility of peripheral biomarkers of oxidative stress, such as isoprostanes, during the periconception period remains underexplored. We evaluated the relationship between isoprostanes during preconception and gestational week 4 and women's reproductive health outcomes.

METHODS

The Effects of Aspirin in Gestation and Reproduction trial (2007-2011) enrolled 1228 women attempting pregnancy and followed them for up to 6 menstrual cycles and throughout pregnancy if they became pregnant. We measured creatinine-adjusted, log-transformed isoprostanes 8-iso-prostaglandin F 2α (8-iso-PGF2α), its metabolite 2,3-dinor-iPF2α-III, and stereoisomers 5-iso-PGF2α-VI and 8,12-iso-iPF2α-VI in urine during preconception and 4 weeks gestation. We evaluated pregnancy among participants in each menstrual cycle using human chorionic gonadotropin (hCG) and defined pregnancy loss as observed loss following positive hCG. We calculated fecundability odds ratios (FOR) and 95% confidence intervals (CI) using discrete-time Cox proportional hazards models and relative risk of pregnancy loss using adjusted log-binomial models.

RESULTS

Higher preconception isoprostane levels were associated with lower fecundability [e.g., FOR = 0.89; 95% CI = 0.81, 0.97 per interquartile range (IQR) increase in 8-iso-PGF2α]. Among 797 pregnancies, isoprostane levels increased from preconception to 4 weeks gestation (e.g., mean difference = 0.12; 95% CI = 0.10, 0.14 ng/mL for 8-iso-PGF2α) and higher isoprostanes at 4 weeks gestation were associated with lower risk of pregnancy loss (e.g., RR = 0.79; 95% CI = 0.62, 1.00 per IQR increase in 8-iso-PGF2α).

CONCLUSIONS

Preconception urinary isoprostanes may identify redox stress pathways associated with lower fecundability. However, the increase in isoprostanes into gestational week 4 and the associated lower risk of pregnancy loss may suggest confounding by latent factors in early pregnancy.

Vascular Effects, Potential Pathways and Mediators of Fetal Exposure to Alcohol and Cigarette Smoking during Pregnancy: A Narrative Review

(1) Background: Programming of atherosclerosis results in vascular structure and function alterations, which may be attributed to fetal exposure to maternal tobacco smoking, alcohol consumption and several lifestyle factors in the first few years of life. This review aims to study the effects of teratogen exposure in utero on vascular dysfunction in offspring and consider mediators and pathways originating from the fetal environment. (2) Methods: Eligible studies were identified in the PubMed, Scopus and Web of Science databases. After the full-text screening, 20 articles were included in the narrative synthesis. (3) Results: The literature presents evidence supporting the detrimental effects of fetal exposure to tobacco smoking on vascular alterations in both human and animal studies. Alcohol exposure impaired endothelial dilation in animal studies, but human studies on both tobacco and alcohol exposure are still sparse. Reduction in nitric oxide (NO) bioavailability and alterations in the epigenome in infants through the upregulation of pro-oxidative and proinflammatory genes may be the common denominators. (4) Conclusion: While maternal smoking and alcohol consumption have more negative outcomes on the infant in the short term, several factors during the first few years of life may mediate the development of vascular dysfunction. Therefore, more prospective studies are needed to ascertain the long-term effects of teratogen exposure, specifically in South Africa.

Urinary oxidative stress biomarkers are associated with preterm birth: an Environmental Influences on Child Health Outcomes program study

BACKGROUND

Preterm birth is the leading cause of infant morbidity and mortality worldwide. Elevated levels of oxidative stress have been associated with an increased risk of delivering before term. However, most studies testing this hypothesis have been conducted in racially and demographically homogenous study populations, which do not reflect the diversity within the United States.

OBJECTIVE

We leveraged 4 cohorts participating in the Environmental Influences on Child Health Outcomes Program to conduct the largest study to date examining biomarkers of oxidative stress and preterm birth (N=1916). Furthermore, we hypothesized that elevated oxidative stress would be associated with higher odds of preterm birth, particularly preterm birth of spontaneous origin.

STUDY DESIGN

This study was a pooled analysis and meta-analysis of 4 birth cohorts spanning multiple geographic regions in the mainland United States and Puerto Rico (208 preterm births and 1708 full-term births). Of note, 8-iso-prostaglandin-F2α, 2,3-dinor-5,6-dihydro-8-iso-prostaglandin-F2α (F2-IsoP-M; the major 8-iso-prostaglandin-F2α metabolite), and prostaglandin-F2α were measured in urine samples obtained during the second and third trimesters of pregnancy. Logistic regression was used to calculate adjusted odds ratios and 95% confidence intervals for the associations between averaged biomarker concentrations for each participant and all preterm births, spontaneous preterm births, nonspontaneous preterm births (births of medically indicated or unknown origin), and categories of preterm birth (early, moderate, and late). Individual oxidative stress biomarkers were examined in separate models.

RESULTS

Approximately 11% of our analytical sample was born before term. Relative to full-term births, an interquartile range increase in averaged concentrations of F2-IsoP-M was associated with higher odds of all preterm births (odds ratio, 1.29; 95% confidence interval, 1.11-1.51), with a stronger association observed for spontaneous preterm birth (odds ratio, 1.47; 95% confidence interval, 1.16-1.90). An interquartile range increase in averaged concentrations of 8-iso-prostaglandin-F2α was similarly associated with higher odds of all preterm births (odds ratio, 1.19; 95% confidence interval, 0.94-1.50). The results from our meta-analysis were similar to those from the pooled combined cohort analysis.

CONCLUSION

Here, oxidative stress, as measured by 8-iso-prostaglandin-F2α, F2-IsoP-M, and prostaglandin-F2α in urine, was associated with increased odds of preterm birth, particularly preterm birth of spontaneous origin and delivery before 34 completed weeks of gestation.

Associations between social, biologic, and behavioral factors and biomarkers of oxidative stress during pregnancy: Findings from four ECHO cohorts

BACKGROUND

Lower socioeconomic status (SES) and elevated psychosocial stress are known contributors to adverse pregnancy outcomes; however, biological mechanisms linking these factors to adverse pregnancy outcomes are not well-characterized. Oxidative stress may be an important, yet understudied mechanistic pathway. We used a pooled study design to examine biological, behavioral, and social factors as predictors of prenatal oxidative stress biomarkers.

METHODS

Leveraging four pregnancy cohorts from the Environmental influences on Child Health Outcomes (ECHO) Program spanning multiple geographic regions across the United States (U.S.) (N = 2082), we measured biomarkers of oxidative stress in urine samples at up to three time points during pregnancy, including 8-isoprostane-prostaglandin F2α (8-isoPGF2α), its major metabolite, 2,3-dinor-5,6-dihydro-15-F2t-isoprostane, and prostaglandin F2α (PGF2α). Maternal age, pre-pregnancy body mass index, marital/partnered status, parity, and smoking status were included as biological and behavioral factors while race/ethnicity, maternal education, and stressful life events were considered social factors. We examined associations between each individual biological, behavioral, and social factor with oxidative stress biomarkers using multivariable-adjusted linear mixed models.

RESULTS

Numerous biological, behavioral, and social factors were associated with elevated levels of 8-isoPGF2α, its major metabolite, and PGF2α. Pregnant people who were current smokers relative to non-smokers or had less than a high school education relative to a college degree had 11.04% (95% confidence interval [CI] = -1.97%, 25.77%) and 9.13% (95% CI = -1.02%, 20.32%) higher levels of 8-isoPGF2α, respectively.

CONCLUSIONS

Oxidative stress biomarkers are elevated among pregnant people with higher socioeconomic disadvantage and may represent one pathway linking biological, behavioral, and social factors to adverse pregnancy and child health outcomes, which should be explored in future work.

Serum metabolomics of end-stage renal disease patients with depression: potential biomarkers for diagnosis

Background

End-stage renal disease (ESRD) is the final stage during the development of renal failure. Depression is the most common psychiatric disorder in patients with ESRD, which in turn aggravates the progression of renal failure, however, its underlying mechanism remains unclear. This study aimed to reveal the pathogenesis and to discover novel peripheral biomarkers for ESRD patients with depression through metabolomic analysis.

Methods

Ultra-high-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) was used to explore changes of serum metabolites among healthy controls, ESRD patients with or without depression. The differential metabolites between groups were subjected to clustering analysis, pathway analysis, receiver operating characteristic (ROC) curve analysis.

Results

A total of 57 significant serum differential metabolites were identified between ESRD patients with or without depression, which were involved in 19 metabolic pathways, such as energy metabolism, glycerolipid metabolism, and glutamate-centered metabolism. Moreover, the area under the ROC curve of gentisic acid, uric acid, 5-hydroxytryptamine, 2-phosphoglyceric acid, leucyl-phenylalanine, propenyl carnitine, naloxone, pregnenolone, 6-thioxanthene 5'-monophosphate, hydroxyl ansoprazole, zileuton O-glucuronide, cabergoline, PA(34:2), PG(36:1), probucol and their combination was greater than 0.90.

Conclusions

Inflammation, oxidative stress and energy metabolism abnormalities, glycerolipid metabolism, and glutamate-centered metabolism are associated with the pathogenesis of ESRD with depression, which may be promising targets for therapy. Furthermore, the identified differential metabolites may serve as biomarkers for the diagnosis of ESRD patients with depression.

Associations of mixture of air pollutants with estimated 10-year atherosclerotic cardiovascular disease risk modified by socio-economic status: The Henan Rural Cohort Study

BACKGROUND

Low socio-economic status (SES) and exposure to single-air pollutant relate to increased prevalent atherosclerotic cardiovascular diseases (ASCVD), however, interactive effect between SES and exposure to single- or multiple-air pollutants on high 10-year ASCVD risk remains unclear.

METHODS

A total of 31,162 individuals were derived from the Henan Rural Cohort Study. Concentrations of air pollutants (particulate matter with an aerodynamic diameter ≤ 1.0 μm (PM₁), ≤2.5 μm (PM_2.5) or ≤10 μm (PM₁₀), nitrogen dioxide (NO₂)) were assessed using a spatiotemporal model based on satellites data. Independent and joint associations of SES, single- and multiple- air pollutants with high 10-year ASCVD risk were evaluated using logistic regression models, quantile g-computation and structural equation models. The interactive effects of SES and exposure to single- or multiple air pollutants on high 10-year ASCVD risk were visualized by using Interaction plots.

RESULTS

Exposure to single air pollutant (PM₁, PM_2.5, PM₁₀ or NO₂) related to increased high 10-year ASCVD risk among individuals with low education level or personal average monthly income, compared to the ones with high education level or personal average monthly income. Furthermore, similar results of exposure to mixture of air pollutants with high 10-year ASCVD risk were observed. Positive interactive effects between low SES and exposure to high single air pollutant or the mixture of air pollutants on high 10-year ASCVD risk were observed.

CONCLUSION

Positive association of low SES with high 10-year ASCVD risk was amplified by exposure to high levels of single air pollutant or a mixture of air pollutants, implying that individuals with low SES may more susceptible to air pollution-related adverse health effect.

Contribution of Adipose Tissue Oxidative Stress to Obesity-Associated Diabetes Risk and Ethnic Differences: Focus on Women of African Ancestry

Adipose tissue (AT) storage capacity is central in the maintenance of whole-body homeostasis, especially in obesity states. However, sustained nutrients overflow may dysregulate this function resulting in adipocytes hypertrophy, AT hypoxia, inflammation and oxidative stress. Systemic inflammation may also contribute to the disruption of AT redox equilibrium. AT and systemic oxidative stress have been involved in the development of obesity-associated insulin resistance (IR) and type 2 diabetes (T2D) through several mechanisms. Interestingly, fat accumulation, body fat distribution and the degree of how adiposity translates into cardio-metabolic diseases differ between ethnicities. Populations of African ancestry have a higher prevalence of obesity and higher T2D risk than populations of European ancestry, mainly driven by higher rates among African women. Considering the reported ethnic-specific differences in AT distribution and function and higher levels of systemic oxidative stress markers, oxidative stress is a potential contributor to the higher susceptibility for metabolic diseases in African women. This review summarizes existing evidence supporting this hypothesis while acknowledging a lack of data on AT oxidative stress in relation to IR in Africans, and the potential influence of other ethnicity-related modulators (e.g., genetic-environment interplay, socioeconomic factors) for consideration in future studies with different ethnicities.

Psychosocial status modifies the effect of maternal blood metal and metalloid concentrations on birth outcomes

BACKGROUND

Metal exposure and psychosocial stress in pregnancy have each been associated with adverse birth outcomes, including preterm birth and low birth weight, but no study has examined the potential interaction between them.

OBJECTIVES

We examined the modifying effect of psychosocial stress on the association between metals and birth outcomes among pregnant women in Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) birth cohort study.

METHODS

In our analysis of 682 women from the PROTECT study, we measured 16 essential and non-essential metals in blood samples at two time points. We administered questionnaires to collect information on depression, perceived stress, social support, and life experience during pregnancy. Using K-means clustering, we categorized pregnant women into one of two groups: "good" and "poor" psychosocial status. We then evaluated whether the effect of blood metals (geometric average) on adverse birth outcomes (gestational age, preterm birth [overall and spontaneous], birth weight z-score, small for gestation [SGA], large for gestation [LGA]) vary between two clusters of women, adjusting for maternal age, maternal education, pre-pregnancy body mass index (BMI), and second-hand smoke exposure.

RESULTS

Blood manganese (Mn) was associated with an increased odds ratio (OR) of overall preterm birth (OR/interquartile range [IQR] = 2.76, 95% confidence interval [CI] = 1.25, 6.12) and spontaneous preterm birth (OR/IQR: 3.68, 95% CI: 1.20, 6.57) only among women with "poor" psychosocial status. The association between copper (Cu) and SGA was also statistically significant only among women having "poor" psychosocial status (OR/IQR: 2.81, 95% CI: 1.20, 6.57). We also observed associations between nickel (Ni) and preterm birth and SGA that were modified by psychosocial status during pregnancy.

CONCLUSIONS

Presence of "poor" psychosocial status intensified the adverse associations between Mn and preterm birth, Cu and SGA, and protective effects of Ni on preterm. This provides evidence that prenatal psychosocial stress may modify vulnerability to metal exposure.

Environmental risk factors and their footprints in vivo - A proposal for the classification of oxidative stress biomarkers

Environmental agents, including socioeconomic condition, and host factors can act as causal agents and risk factors in disease. We use biomarkers and sociomarkers to study causal factors, such as overproduction of reactive oxygen species (ROS) which could play a role in disease through oxidative stress. It is therefore important to define the exact meaning of the biomarker we measure. In this review we attempt a classification of biomarkers related to oxidative stress based on their biological meaning. We define as type zero biomarkers the direct measurement of ROS in vivo in patients. Type 1 biomarkers are the most frequently used indicators of oxidative stress, represented by oxidized lipids, proteins or nucleic acids and their bases. Type 2 biomarkers are indicators of the activation of biochemical pathways that can lead to the formation of ROS. Type 3 biomarkers are host factors such as small-molecular weight antioxidants and antioxidant enzymes, while type 4 biomarkers measure genetic factors and mutations that could modify the susceptibility of an individual to oxidative stress. We also discuss whether biomarkers are actionable or not, that is if the specific blockade of these molecules can ameliorate disease or if they are just surrogate markers.

The proposed classification of biomarkers of oxidative stress based on their meaning and ambiguities, within the theoretical framework of the oxidative stress theory of disease may help identify those diseases, and individuals, where oxidative stress has a causal role, to allow targeted therapy and personalized medicine.

Repeated measures of urinary oxidative stress biomarkers and preterm birth in Puerto Rico

BACKGROUND

Preterm birth (PTB; gestational age <37 weeks), the leading cause of infant morbidity and mortality worldwide, is of particular concern in Puerto Rico. Rates of PTB in Puerto Rico peaked at 20% in 2006, which are historically some of the highest in the world. Oxidative stress and inflammation have been implicated as contributors to adverse birth outcomes, including PTB, and these associations have not been explored in Puerto Rico. Our objective was to examine associations between urinary oxidative stress biomarkers and PTB in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) pregnancy cohort (N = 469).

METHODS

8-iso-prostaglandin F2α (8-iso-PGF2α), its primary metabolite, and prostaglandin F2α (PGF2α) were included as biomarkers of oxidative stress or inflammation. Biomarkers were measured in urine samples collected at up to 3 timepoints across pregnancy (mean 18, 24, 28 weeks gestation). We quantified the proportion of 8-iso-PGF2α originating from oxidative stress and inflammation pathways with a formula based on the ratio of 8-iso-PGF2α to PGF2α. Logistic regression models were used to calculate adjusted odds ratios (OR) for associations between average biomarker concentrations from each woman (visits 1-3) and PTB. Associations between biomarker concentrations at each study visit and PTB were analyzed in separate models.

RESULTS

Averaged levels of 8-iso-PGF2α, its primary metabolite, and PGF2α were associated with increased odds of PTB (OR = 1.64, 95% confidence interval [CI] = 1.07-2.54; OR = 1.79, 95% CI = 1.14-2.84; OR = 1.98, 95% CI = 1.32-3.02, respectively). Odds ratios for PTB were greater in magnitude in association with oxidative stress biomarkers measured later in pregnancy. The fraction of 8-iso-PGF2α derived from inflammation was associated with PTB (OR = 1.73, 95% CI = 1.09, 2.93), while the fraction of 8-iso-PGF2α derived from oxidative stress was not associated with PTB (OR = 1.17, 95% CI = 0.90, 1.54).

CONCLUSIONS

Our results suggest that oxidative stress and inflammation, as measured by these biomarkers, may be important contributors to PTB. Further research is needed to improve our understanding of the role these biomarkers may play in the causal pathway between environmental factors and PTB.

Joint impact of phthalate exposure and stressful life events in pregnancy on preterm birth

BACKGROUND

Urinary phthalate metabolites and psychosocial stress in pregnancy have each been associated with preterm birth (PTB), but no study has examined the joint impact of these two environmental exposures. We hypothesized that there would be stronger associations between phthalate exposure and PTB in mothers with higher stress in pregnancy compared to mothers with lower stress.

METHODS

We addressed this question using data from The Infant Development and the Environment Study (TIDES), a prospective birth cohort conducted at four US sites (N = 783). We examined urinary phthalate metabolite concentrations measured in samples collected from up to three trimesters of pregnancy. Mothers reported their exposure to stressful life events (SLE) in each trimester in a questionnaire administered in the third trimester. PTB was defined as delivery before 37 weeks completed gestation (n = 71, 9.1%). We examined associations between urinary phthalate metabolite concentrations (individual time points and on average) and PTB using logistic regression models adjusted for maternal race, age, pre-pregnancy body mass index, education, specific gravity, and gestational age at sample collection. In addition, we created models stratified by whether or not mothers were exposed to any or no SLE in pregnancy.

RESULTS

Summed di-2-ethylhexyl phthalate (ΣDEHP) metabolites measured in urine samples from the third trimester, but not the first trimester, were associated with an increased odds ratio (OR) of PTB (OR = 1.44, 95% confidence interval [CI] = 1.06, 1.95). In models stratified by SLE, associations between third trimester ΣDEHP concentrations and PTB were significant only for women experiencing one or more SLE during pregnancy (OR for ΣDEHP: 2.09, 95% CI: 1.29, 3.37) but not for women with no SLE during pregnancy (OR for ΣDEHP: 1.04, 95% CI: 0.66, 1.63) (p for interaction = 0.07).

CONCLUSIONS

We observed an association between urinary ΣDEHP levels and PTB that was modified by whether a mother was exposed to one or more psychosocial stressors during pregnancy. Additional research to understand the joint impacts of chemical and non-chemical exposures, with an emphasis on timing of exposure, is needed in order to advance the state of the science on how the environment influences pregnancy.