Dataset Information

Statistical methods for modeling repeated measures of maternal environmental exposure biomarkers during pregnancy in association with preterm birth.

ABSTRACT:

Background

It is of critical importance to evaluate the role of environmental chemical exposures in premature birth. While a number of studies investigate this relationship, most utilize single exposure measurements during pregnancy in association with the outcome. The studies with repeated measures of exposure during pregnancy employ primarily cross-sectional analyses that may not be fully leveraging the power and additional information that the data provide.

Methods

We examine 9 statistical methods that may be utilized to estimate the relationship between a longitudinal exposure and a binary, non-time-varying outcome. To exemplify these methods we utilized data from a nested case-control study examining repeated measures of urinary phthalate metabolites during pregnancy in association with preterm birth.

Results

The methods summarized may be useful for: 1) Examining sensitive windows of exposure in association with an outcome; 2) Summarizing repeated measures to estimate the relationship between average exposure and an outcome; 3) Identifying acute exposures that may be relevant to the outcome; and 4) Understanding the contribution of temporal patterns in exposure levels to the outcome of interest. In the study of phthalates, changes in urinary metabolites over pregnancy did not appear to contribute significantly to preterm birth, making summary of average exposure across gestation optimal given the current design.

Conclusions

The methods exemplified may be of great use in future epidemiologic research projects intended to: 1) Elucidate the complex relationships between environmental chemical exposures and preterm birth; 2) Investigate biological mechanisms in prematurity using repeated measures of maternal factors throughout pregnancy; and 3) More generally, address the relationship between a longitudinal predictor and a binary, non-time-varying outcome.

SUBMITTER: Chen YH

PROVIDER: S-EPMC4417225 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Publications

Statistical methods for modeling repeated measures of maternal environmental exposure biomarkers during pregnancy in association with preterm birth.

Chen Yin-Hsiu YH Ferguson Kelly K KK Meeker John D JD McElrath Thomas F TF Mukherjee Bhramar B

Environmental health : a global access science source 20150126

<h4>Background</h4>It is of critical importance to evaluate the role of environmental chemical exposures in premature birth. While a number of studies investigate this relationship, most utilize single exposure measurements during pregnancy in association with the outcome. The studies with repeated measures of exposure during pregnancy employ primarily cross-sectional analyses that may not be fully leveraging the power and additional information that the data provide.<h4>Methods</h4>We examine 9 ...[more]

PMID: 25619201

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Project description:BackgroundMediation analysis is useful for understanding mechanisms and has been used minimally in the study of the environment and disease.ObjectiveWe examined mediation of the association between phthalate exposure during pregnancy and preterm birth by oxidative stress.MethodsThis nested case-control study of preterm birth (n = 130 cases, 352 controls) included women who delivered in Boston, Massachusestts, from 2006 through 2008. Phthalate metabolites and 8-isoprostane, an oxidative stress biomarker, were measured in urine from three visits in pregnancy. We applied four counterfactual mediation methods: method 1, utilizing exposure and mediator averages; method 2, using averages but allowing for an exposure-mediator interaction; method 3, incorporating longitudinal measurements of the exposure and mediator; and method 4, using longitudinal measurements and allowing for an exposure-mediator interaction.ResultsWe observed mediation of the associations between phthalate metabolites and all preterm birth by 8-isoprostane, with the greatest estimated proportion mediated observed for spontaneous preterm births specifically. Fully utilizing repeated measures of the exposure and mediator improved precision of indirect (i.e., mediated) effect estimates, and including an exposure-mediator interaction increased the estimated proportion mediated. For example, for mono(2-ethyl-carboxy-propyl) phthalate (MECPP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), the percent of the total effect mediated by 8-isoprostane increased from 47% to 60% with inclusion of an exposure-mediator interaction term, in reference to a total adjusted odds ratio of 1.67 or 1.48, respectively.ConclusionsThis demonstrates mediation of the phthalate-preterm birth relationship by oxidative stress, and the utility of complex regression models in capturing mediated associations when repeated measures of exposure and mediator are available and an exposure-mediator interaction may exist. Citation: Ferguson KK, Chen YH, VanderWeele TJ, McElrath TF, Meeker JD, Mukherjee B. 2017. Mediation of the relationship between maternal phthalate exposure and preterm birth by oxidative stress with repeated measurements across pregnancy. Environ Health Perspect 125:488-494; http://dx.doi.org/10.1289/EHP282.

Project description:IntroductionHuman anelloviruses, including torque teno virus (TTV) and torque teno mini virus (TTMV), are ubiquitous in the general population and have no known pathogenicity. We investigated the prevalence and viral load of TTV and TTMV in plasma and saliva over pregnancy, and assessed their association with spontaneous or medically indicated preterm birth.MethodsThis is a secondary analysis of the Measurement of Maternal Stress (MOMS) study, which recruited 744 individuals with singleton pregnancies from 4 US sites (Chicago, Pittsburgh, San Antonio, and rural Pennsylvania). Baseline outpatient visits took place in the second trimester (between 12'0 and 20'6/7 weeks' gestation), and follow-up visits in the third trimester (between 32'0 and 35'6/7 weeks' gestation). In a case-control study design, participants who delivered preterm (<37 weeks) resulting from spontaneous labor and/or preterm premature rupture of membranes ("sPTB") were compared with participants experiencing medically indicated preterm birth ("iPTB"), or delivery at term ("controls"). Plasma and saliva samples obtained during the second and third trimesters were tested for the presence and quantity of TTV and TTMV using real-time PCR. Demographic data were obtained via self-report, and clinical data via medical record review by trained research personnel.ResultsTTV was detected in plasma from 81% (second trimester) and 77% (third trimester) of participants, and in saliva from 64 and 60%. Corresponding detection rates for TTMV were 59 and 41% in plasma, and 35 and 24% in saliva. TTV and TTMV concentrations were similar between matched plasma and saliva samples. TTV prevalence and concentrations were not significantly different between groups (sPTB, iPTB, and controls). However, plasma TTMV in the third trimester was associated with sPTB and earlier gestational age at delivery. The iPTB group was not different from either the sPTB or the control group. In saliva, concentrations of TTV and TTMV were similar among the three groups. Both TTV and TTMV were more prevalent with increasing parity and were more common in Black and Hispanic participants compared to non-Hispanic White participants.ConclusionAnellovirus presence (specifically, TTMV) in the third trimester may be associated with preterm birth. Whether this association is causative remains to be determined.

Project description:BACKGROUND:A number of phenols and parabens are added to consumer products for a variety of functions, and have been found at detectable levels in the majority of the U.S. POPULATION:Among other functions, thyroid hormones are essential in fetal neurodevelopment, and could be impacted by the endocrine disrupting effects of phenols and parabens. The present study investigated the association between ten maternal urinary phenol and paraben biomarkers (bisphenol S, triclosan, triclocarban, benzophenone-3, 2,4-dichlorophenol, 2,5-dichlorophenol, and ethyl, butyl, methyl and propyl paraben) and four plasma thyroid hormones in 439 pregnant women in a case-control sample nested within a cohort study based in Boston, MA. METHODS:Urine and blood samples were collected from up to four visits during pregnancy (median weeks of gestation at each visit: Visit 1: 9.64, Visit 2: 17.9, Visit 3: 26.0, Visit 4: 35.1). Linear mixed models were constructed to take into account the repeated measures jointly, followed by multivariate linear regression models stratified by gestational age to explore potential windows of susceptibility. RESULTS:We observed decreased total triiodothyronine (T3) in relation to an IQR increase in benzophenone-3 (percent change [%?]?=?-2.07; 95% confidence interval [CI]?=?-4.16, 0.01), butyl paraben (%??=?-2.76; 95% CI?=?-5.25, -0.26) and triclosan (%??=?-2.53; 95% CI?=?-4.75, -0.30), and triclocarban at levels above the LOD (%??=?-5.71; 95% CI?=?-10.45, -0.97). A 2.41% increase in T3 was associated with an IQR increase in methyl paraben (95% CI?=?0.58, 4.24). We also detected a negative association between free thyroxine (FT4) and propyl paraben (%??=?-3.14; 95% CI?=?-6.12, -0.06), and a suggestive positive association between total thyroxine (T4) and methyl paraben (%??=?1.19; 95% CI?=?-0.10, 2.47). Gestational age-specific multivariate regression analyses showed that the magnitude and direction of some of the observed associations were dependent on the timing of exposure. CONCLUSION:Certain phenols and parabens were associated with altered thyroid hormone levels during pregnancy, and the timing of exposure influenced the association between phenol and paraben, and hormone concentrations. These changes may contribute to downstream maternal and fetal health outcomes. Additional research is required to replicate the associations, and determine the potential biological mechanisms underlying the observed associations.

Project description:BACKGROUND:Despite the mainly reassuring outcomes for pregnant women with coronavirus disease 2019 reported by previous case series with small sample sizes, some recent reports of severe maternal morbidity requiring intubation and of maternal deaths show the need for additional data about the impact of coronavirus disease 2019 on pregnancy outcomes. OBJECTIVE:This study aimed to report the maternal characteristics and clinical outcomes of pregnant women with coronavirus disease 2019. STUDY DESIGN:This retrospective, single-center study includes all consecutive pregnant women with confirmed (laboratory-confirmed) or suspected (according to the Chinese management guideline [version 7.0]) coronavirus disease 2019, regardless of gestational age at diagnosis, admitted to the Strasbourg University Hospital (France) from March 1, 2020, to April 3, 2020. Maternal characteristics, laboratory and imaging findings, and maternal and neonatal outcomes were extracted from medical records. RESULTS:The study includes 54 pregnant women with confirmed (n=38) and suspected (n=16) coronavirus disease 2019. Of these, 32 had an ongoing pregnancy, 1 had a miscarriage, and 21 had live births: 12 vaginal and 9 cesarean deliveries. Among the women who gave birth, preterm deliveries were medically indicated for their coronavirus disease 2019-related condition for 5 of 21 women (23.8%): 3 (14.3%) before 32 weeks' gestation and 2 (9.5%) before 28 weeks' gestation. Oxygen support was required for 13 of 54 women (24.1%), including high-flow oxygen (n=2), noninvasive (n=1) and invasive (n=3) mechanical ventilation, and extracorporeal membrane oxygenation (n=1). Of these, 3, aged 35 years or older with positive test result for severe acute respiratory syndrome coronavirus 2 using reverse transcription polymerase chain reaction, had respiratory failure requiring indicated delivery before 29 weeks' gestation. All 3 women were overweight or obese, and 2 had an additional comorbidity. CONCLUSION:Coronavirus disease 2019 in pregnancy was associated with maternal morbidity and preterm birth. Its association with other well-known risk factors for severe maternal morbidity in pregnant women with no infection, including maternal age above 35 years, overweight, and obesity, suggests further studies are required to determine whether these risk factors are also associated with poorer maternal outcome in these women.

Project description:BACKGROUND:Maintaining thyroid homeostasis during pregnancy is essential for normal fetal growth and development. Growing evidence suggests that phthalates interfere with normal thyroid function. Few human studies have investigated the degree to which phthalates may affect thyroid hormone levels in particularly susceptible populations such as pregnant women. OBJECTIVES:We examined the associations between repeated measures of urinary phthalate metabolites and plasma thyroid hormone levels in samples collected at up to four time points per subject in pregnancy. Additionally, we investigated the potential windows of susceptibility to thyroid hormone disturbances related to study visit of sample collection. METHODS:Data were obtained from pregnant women (n = 439) participating in a nested case-control study of preterm birth with 116 cases and 323 controls. We measured 9 phthalate metabolite concentrations in urine samples collected at up to four study visits per subject during pregnancy (median = 10, 18, 26, and 35 weeks of gestation, respectively). We also measured a panel of thyroid function markers in plasma collected at the same four time points per subject during pregnancy. RESULTS:Although our results were generally null, in repeated measures analyses we observed that phthalate metabolites were largely inversely associated with thyrotropin and positively associated with free and total thyroid hormones. Cross-sectional analyses by study visit revealed that the magnitude and/or direction of these relationships varied by timing of exposure during gestation. CONCLUSIONS:These results support previous reports showing the potential for environmental phthalate exposure to alter circulating levels of thyroid hormones in pregnant women. Citation: Johns LE, Ferguson KK, McElrath TF, Mukherjee B, Meeker JD. 2016. Associations between repeated measures of maternal urinary phthalate metabolites and thyroid hormone parameters during pregnancy. Environ Health Perspect 124:1808-1815;?http://dx.doi.org/10.1289/EHP170.

Project description:ObjectiveTo examine the relationship between maternal characteristics, serum biomarkers and preterm birth (PTB) by spontaneous and medically indicated subtypes.DesignPopulation-based cohort.SettingCalifornia, United States of America.PopulationFrom a total population of 1 004 039 live singleton births in 2009 and 2010, 841 665 pregnancies with linked birth certificate and hospital discharge records were included.MethodsCharacteristics were compared for term and preterm deliveries by PTB subtype using logistic regression and odds ratios adjusted for maternal characteristics and obstetric factors present in final stepwise models and 95% confidence intervals. First-trimester and second-trimester serum marker levels were analysed in a subset of 125 202 pregnancies with available first-trimester and second-trimester serum biomarker results.Main outcome measurePTB by subtype.ResultsIn fully adjusted models, ten characteristics and three serum biomarkers were associated with increased risk in each PTB subtype (Black race/ethnicity, pre-existing hypertension with and without pre-eclampsia, gestational hypertension with pre-eclampsia, pre-existing diabetes, anaemia, previous PTB, one or two or more previous caesarean section(s), interpregnancy interval ? 60 months, low first-trimester pregnancy-associated plasma protein A, high second-trimester ?-fetoprotein, and high second-trimester dimeric inhibin A). These risks occurred in 51.6-86.2% of all pregnancies ending in PTB depending on subtype. The highest risk observed was for medically indicated PTB <32 weeks in women with pre-existing hypertension and pre-eclampsia (adjusted odds ratio 89.7, 95% CI 27.3-111.2).ConclusionsOur findings suggest a shared aetiology across PTB subtypes. These commonalities point to targets for further study and exploration of risk reduction strategies.Tweetable abstractFindings suggest a shared aetiology across preterm birth subtypes. Patterns may inform risk reduction efforts.

Dataset Information

Statistical methods for modeling repeated measures of maternal environmental exposure biomarkers during pregnancy in association with preterm birth.

Background

Methods

Results

Conclusions

Publications

Statistical methods for modeling repeated measures of maternal environmental exposure biomarkers during pregnancy in association with preterm birth.

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