Preterm birth is a leading cause of neonatal mortality, with a variety of contributing causes and risk factors. Environmental exposures represent a group of understudied, but potentially important, ...factors. Phthalate diesters are used extensively in a variety of consumer products worldwide. Consequently, exposure in pregnant women is highly prevalent.
To assess the relationship between phthalate exposure during pregnancy and preterm birth.
This nested case-control study was conducted at Brigham and Women's Hospital, Boston, Massachusetts. Women were recruited for a prospective observational cohort study from 2006-2008. Each provided demographic data, biological samples, and information about birth outcomes. From within this group, we selected 130 cases of preterm birth and 352 randomly assigned control participants, and we analyzed urine samples from up to 3 time points during pregnancy for levels of phthalate metabolites.
Phthalate exposure during pregnancy.
We examined associations between average levels of phthalate exposure during pregnancy and preterm birth, defined as fewer than 37 weeks of completed gestation, as well as spontaneous preterm birth, defined as preterm preceded by spontaneous preterm labor or preterm premature rupture of the membranes (n = 57).
Geometric means of the di-2-ethylhexyl phthalate (DEHP) metabolites mono-(2-ethyl)-hexyl phthalate (MEHP) and mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), as well as mono-n-butyl phthalate (MBP), were significantly higher in cases compared with control participants. In adjusted models, MEHP, MECPP, and Σ DEHP metabolites were associated with significantly increased odds of preterm birth. When spontaneous preterm births were examined alone, MEHP, mono-(2-ethyl-5-oxohexyl) phthalate, MECPP, Σ DEHP, MBP, and mono-(3-carboxypropyl) phthalate metabolite levels were all associated with significantly elevated odds of prematurity.
Women exposed to phthalates during pregnancy have significantly increased odds of delivering preterm. Steps should be taken to decrease maternal exposure to phthalates during pregnancy.
Background Preeclampsia is a prevalent and enigmatic disease, in part characterized by poor remodeling of the spiral arteries. However, preeclampsia does not always clinically present when remodeling ...has failed to occur. Hypotheses surrounding the “second hit” that is necessary for the clinical presentation of the disease focus on maternal inflammation and oxidative stress. Yet, the studies to date that have investigated these factors have used cross-sectional study designs or small study populations. Objective In the present study, we sought to explore longitudinal trajectories, beginning early in gestation, of a panel of inflammation and oxidative stress markers in women who went on to have preeclamptic or normotensive pregnancies. Study Design We examined 441 subjects from the ongoing LIFECODES prospective birth cohort, which included 50 mothers who experienced preeclampsia and 391 mothers with normotensive pregnancies. Participants provided urine and plasma samples at 4 time points during gestation (median, 10, 18, 26, and 35 weeks) that were analyzed for a panel of oxidative stress and inflammation markers. Oxidative stress biomarkers included 8-isoprostane and 8-hydroxydeoxyguanosine. Inflammation biomarkers included C-reactive protein, the cytokines interleukin-1β, -6, and -10, and tumor necrosis factor-α. We created Cox proportional hazard models to calculate hazard ratios based on time of preeclampsia diagnosis in association with biomarker concentrations at each of the 4 study visits. Results In adjusted models, hazard ratios of preeclampsia were significantly ( P <.01) elevated in association with all inflammation biomarkers that were measured at visit 2 (median, 18 weeks; hazard ratios, 1.31–1.83, in association with an interquartile range increase in biomarker). Hazard ratios at this time point were the most elevated for C-reactive protein, for interleukin-1β, -6, and -10, and for the oxidative stress biomarker 8-isoprostane (hazard ratio, 1.68; 95% confidence interval, 1.14–2.48) compared to other time points. Hazard ratios for tumor necrosis factor-α were consistently elevated at all 4 of the study visits (hazard ratios, 1.49–1.63; P <.01). In sensitivity analyses, we observed that these associations were attenuated within groups typically at higher risk of experiencing preeclampsia, which include African American mothers, mothers with higher body mass index at the beginning of gestation, and pregnancies that ended preterm. Conclusions This study provides the most robust data to date on repeated measures of inflammation and oxidative stress in preeclamptic compared with normotensive pregnancies. Within these groups, inflammation and oxidative stress biomarkers show different patterns across gestation, beginning as early as 10 weeks. The start of the second trimester appears to be a particularly important time point for the measurement of these biomarkers. Although biomarkers alone do not appear to be useful in the prediction of preeclampsia, these data are useful in understanding the maternal inflammatory profile in pregnancy before the development of the disease and may be used to further develop an understanding of potentially preventative measures.
The concept that preeclampsia is a multisystemic syndrome is appreciated in both research and clinical care. Our understanding of pathophysiology recognizes the role of inflammation, oxidative and ...endoplasm reticulum stress, and angiogenic dysfunction. Yet, we have not progressed greatly toward clinically useful prediction nor had substantial success in prevention or treatment. One possibility is that the maternal syndrome may be reached through different pathophysiological pathways, that is, subtypes of preeclampsia, that in their specificity yield more clinical utility. For example, early and late onset preeclampsia are increasingly acknowledged as different pathophysiological processes leading to a common presentation. Other subtypes of preeclampsia are supported by disparate clinical outcomes, long-range prognosis, organ systems involved, and risk factors. These insights have been supplemented by discovery-driven methods, which cluster preeclampsia cases into groups indicating different pathophysiologies. In this presentation, we review likely subtypes based on current knowledge and suggest others. We present a consideration of the requirements for a clinically meaningful preeclampsia subtype. A useful subtype should (1) identify a specific pathophysiological pathway or (2) specifically indicate maternal or fetal outcome, (3) be recognizable in a clinically useful time frame, and (4) these results should be reproducible and generalizable (but at varying frequency) including in low resource settings. We recommend that the default consideration be that preeclampsia includes several subtypes rather than trying to force all cases into a single pathophysiological pathway. The recognition of subtypes and deciphering their different pathophysiologies will provide specific targets for prevention, prediction, and treatment directing personalized care.
We conducted a literature review on the studies that investigated the relationship of preterm birth, including spontaneous preterm birth (sPTB), with vitamin D status. Overall, these studies ...demonstrated that the incidence of sPTB was associated with maternal vitamin D insufficiency in early pregnancy. However, the potential mechanisms and biological pathways are unknown.
To investigate early pregnancy gene expression signatures associated with both vitamin D insufficiency and sPTB. We further constructed a network of these gene signatures and identified the common biological pathways involved.
We conducted peripheral blood transcriptome profiling at 10-18 weeks of gestation in a nested case-control cohort of 24 pregnant women who participated in the Vitamin D Antenatal Asthma Reduction Trial (VDAART). In this cohort, 8 women had spontaneous preterm delivery (21-32 weeks of gestation) and 17 women had vitamin D insufficiency (25-hydroxyvitamin D < 30 ng/mL). We separately identified vitamin D-associated and sPTB gene signatures at 10 to 18 weeks and replicated the overlapping signatures in the mid-pregnancy peripheral blood of an independent cohort with sPTB cases.
At 10-18 weeks of gestation, 146 differentially expressed genes (25 upregulated) were associated with both vitamin D insufficiency and sPTB in the discovery cohort (FDR < 0.05). Of these genes, 43 (25 upregulated) were replicated in the independent cohort of sPTB cases and controls with normal pregnancies (P < 0.05). Functional enrichment and network analyses of the replicated gene signatures suggested several highly connected nodes related to inflammatory and immune responses.
Our gene expression study and network analyses suggest that the dysregulation of immune response pathways due to early pregnancy vitamin D insufficiency may contribute to the pathobiology of sPTB.
Non-persistent chemicals, such as phthalates, environmental phenols, organophosphate pesticides, and others, are challenging to study because of their ubiquity in the environment, diverse exposure ...routes, and high temporal variability of biomarkers. Nonetheless, there is interest in understanding how gestational exposure to these chemicals may affect fetal growth, as perturbations to normal fetal growth are related to a plethora of adverse health outcomes in childhood and adulthood.
The purpose of this review is to describe the state of the science on this topic. We searched PubMed for studies that included both 1) biomarkers of non-persistent chemicals collected during pregnancy and 2) fetal growth outcomes measured at birth (e.g., birth weight) or by ultrasound in utero (e.g., estimated fetal weight).
The bulk of the literature we found uses biomarkers measured at a single time point in pregnancy and birth weight as the primary measure of fetal growth. There is a small, but growing, body of research that uses ultrasound measures to assess fetal growth during pregnancy. In addition to summarizing the findings of the publications we identified, we describe inconsistencies in methodology, areas for improvement, and gaps in existing knowledge that can be targeted for improvement in future work. This literature is characterized by variability in methodology, likely contributing to the inconsistency of results reported. We further discuss maternal, placental, and fetal pathways by which these classes of chemicals may affect fetal growth.
To improve understanding of how everyday chemical exposures affect fetal growth, and ultimately lifelong health outcomes, mechanisms of toxicant action should be considered alongside improved study designs for future hypothesis-driven research.
Preterm birth is a significant public health problem, affecting over 1 in 10 live births and contributing largely to infant mortality and morbidity. Everyday exposure to environmental chemicals such ...as phthalates could contribute to prematurity, and may be modifiable. In the present study we examine variability in phthalate exposure across gestation and identify windows of susceptibility for the relationship with preterm birth.
Women were recruited early in pregnancy as part of a prospective, longitudinal birth cohort at the Brigham and Women's Hospital in Boston, Massachusetts. Urine samples were collected at up to 4 time points during gestation for phthalate measurement, and birth outcomes were recorded at delivery. From this population we selected all 130 cases of preterm birth, defined as delivery before 37weeks of completed gestation, as well as 352 random controls.
Urinary phthalate metabolite levels were moderately variable over pregnancy, but levels measured at multiple time points were associated with increased odds of preterm birth. Adjusted odds ratios (aOR) for spontaneous preterm birth were strongest in association with phthalate metabolite concentrations measured at the beginning of the third trimester (aOR for summed di-2-ethylhexyl phthalate metabolites ∑DEHP=1.33, 95% confidence interval CI=1.02, 1.73). Odds ratios for placental preterm birth, defined as delivery with presentation of preeclampsia or intrauterine growth restriction, were slightly elevated in the first trimester for DEHP metabolites (aOR for ∑DEHP=1.33, 95% CI=0.99, 1.78).
Pregnant women with exposure to phthalates both early and late in pregnancy are at an increased risk of delivering preterm, but mechanisms may differ based on etiology.
•We examine changes in maternal urinary phthalate metabolites over pregnancy.•We modeled trajectories of metabolites in mothers who delivered preterm vs. term.•We calculated odds of prematurity with phthalates measured at each time point.•Spontaneous preterm birth was associated with 3rd trimester phthalate levels.
Eicosanoids are a class of bioactive lipids produced from the oxygenation of polyunsaturated fatty acid precursors, including the primary omega-6 fatty acids (linoleic acid LA and arachidonic acid ...AA) and omega-3 fatty acids (docosahexaenoic acid DHA and eicosapentaenoic acid EPA) 12. Namely, 1 participant previously categorized as AGA was recategorized as SGA, and 2 participants previously categorized as LGA were recategorized as AGA. ...our final distribution of outcome groups was 31 SGA cases, 31 AGA controls, and 28 LGA cases. Eicosanoid quantification A panel of eicosanoids and fatty acids was measured in plasma samples by the Mass Spectrometry Research and Support Group at the National Institute of Environmental Health Sciences (Research Triangle, NC, US) in 2018. The eicosanoid pathway is defined by a fatty acid precursor—linoleic acid (LA), arachidonic acid (AA), docosahexaenoic acid (DHA), or eicosapentaenoic acid (EPA)—that is metabolized by an enzyme—cytochrome P450 (CYP), lipoxygenase (LOX), or cyclooxygenase (COX).
Maternal exposure to environmental phenols is common in pregnancy and has been linked to preterm birth, preeclampsia, and reduced fetal growth. One potential mechanism may be through increased ...maternal oxidative stress.
We examined the associations between a panel of 10 urinary phenols, including dichlorophenols, benzophenone-3, parabens, triclosan and triclocarban, and bisphenol-S, and two urinary oxidative stress biomarkers, 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane. All exposure and outcome biomarkers were measured at 4 time points in pregnancy.
We used repeated measures models to examine the association between repeated exposure and outcome biomarkers. Additionally, we used adaptive elastic net (AENET) to identify non-null associations accounting for the correlation structure of exposures, both for phenols and urinary phthalate metabolites that were previously associated with the oxidative stress biomarkers in our study population.
In adjusted repeated measures models, we observed that dichlorophenols, benzophenone-3, triclosan, and some parabens were associated with increases in both oxidative stress biomarkers. The greatest effect estimates were observed for 2,5-dichlorophenol; an interquartile range (IQR) increase in this compound was associated with a 15.2% (95% confidence interval CI = 11.0, 19.6) increase in 8-OHdG and a 16.7% (95% CI = 9.66, 24.2) increase in 8-isoprostane. Bisphenol-S detection was associated with a clear increase in 8-isoprostane (18.5%, 95% CI = 7.68, 30.5) but a more modest increase in 8-OHdG (6.18%, 95% CI = −0.27, 13.1). However, AENET models did not consistently select any of the phenols as predictors of 8-OHdG or 8-isoprostane when phthalate metabolites were included in the model.
Overall, urinary phenols were associated with increases in biomarkers of oxidative stress in pregnancy but either to a lesser extent, or due to correlation with, urinary phthalate metabolites.
•We examined the association between urinary phenols and oxidative stress biomarkers.•Urinary exposure and outcome biomarkers were measured at 4 study visits in pregnancy.•Phenols were associated with modest increases in both oxidative stress biomarkers.•AENET selected the drivers of associations from the mixture of phenols and phthalates.•Mixture results suggested phthalates were driving phenol-oxidative stress associations.
Objective The purpose of this study was to investigate oxidative stress as a mechanism of preterm birth in human subjects; we examined associations between urinary biomarkers of oxidative stress that ...were measured at multiple time points during pregnancy and preterm birth. Study Design This nested case-control study included 130 mothers who delivered preterm and 352 mothers who delivered term who were originally recruited as part of an ongoing prospective birth cohort at Brigham and Women’s Hospital. Two biomarkers that included 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine samples that were collected at up to 4 time points (median 10, 18, 26, and 35 weeks) during gestation. Results Urinary concentrations of 8-isoprostane and 8-OHdG decreased and increased, respectively, as pregnancy progressed. Average levels of 8-isoprostane across pregnancy were associated with increased odds of spontaneous preterm birth (adjusted odds ratio, 6.25; 95% confidence interval, 2.86–13.7), and associations were strongest with levels measured later in pregnancy. Average levels of 8-OHdG were protective against overall preterm birth (adjusted odds ratio, 0.19; 95% confidence interval, 0.10–0.34), and there were no apparent differences in the protective effect in cases of spontaneous preterm birth compared with cases of placental origin. Odds ratios for overall preterm birth were more protective in association with urinary 8-OHdG concentrations that were measured early in pregnancy. Conclusion Maternal oxidative stress may be an important contributor to preterm birth, regardless of subtype and timing of exposure during pregnancy. The 2 biomarkers that were measured in the present study had opposite associations with preterm birth; an improved understanding of what each represents may help to identify more precisely important mechanisms in the pathway to preterm birth.
We sought to validate several clinical risk factors previously described for preeclampsia in a large contemporary multicenter prospective cohort.
We enrolled women from three sites before 15 weeks of ...gestation. Demographic and clinical risk factors were collected through standardized chart review. The main outcome of preeclampsia was diagnosed using the American College of Obstetricians and Gynecologists definitions from 2002. Multivariable logistic regression was used to control for confounders.
Two thousand six hundred thirty-seven women are included in this analysis; 237 (9.0%) developed preeclampsia. In adjusted analysis, chronic hypertension (adjusted odds ratio OR 2.72; 95% confidence interval 1.78-4.13), pregestational diabetes (adjusted OR 3.88; 2.08-7.26), multiple gestation (adjusted OR 2.96; 1.74-5.03), African American race (adjusted OR 1.91; 1.35-2.71), prior preeclampsia (adjusted OR 3.63; 2.29-5.73), nulliparity (adjusted OR 1.73; 1.26-2.38), assisted reproductive techniques (adjusted OR: 1.72; 1.10-2.68), and being overweight (adjusted OR for body mass index BMI, kg/m greater than 25-30: 1.65; 1.13-2.41) or obese (adjusted OR for BMI greater than 30-35: 2.34, 1.51-3.61; adjusted OR for BMI greater than 35-40: 3.59, 2.13-6.03; adjusted OR for BMI greater than 40: 6.04, 3.56-10.24) were associated with preeclampsia, but advanced maternal age was not. Similar associations were found for severe preeclampsia. A dose-response effect was observed in the relationship between BMI and both preeclampsia and severe preeclampsia. Being overweight or obese was the most important risk factor for both preeclampsia and severe preeclampsia with an attributable risk percent of 64.9% and 64.4%, respectively.
In this contemporary cohort, increasingly prevalent and potentially modifiable factors were confirmed as significant risk factors for preeclampsia and severe preeclampsia, the most important being overweight or obese. This information is important to guide public health efforts in preeclampsia prevention.
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