Dataset Information

Fetal Thyroid Function, Birth Weight, and in Utero Exposure to Fine Particle Air Pollution: A Birth Cohort Study.

ABSTRACT: BACKGROUND:Thyroid hormones are critical for fetal development and growth. Whether prenatal exposure to fine particle air pollution (? 2.5 ?m; PM2.5) affects fetal thyroid function and what the impact is on birth weight in normal healthy pregnancies have not been studied yet. OBJECTIVES:We studied the impact of third-trimester PM2.5 exposure on fetal and maternal thyroid hormones and their mediating role on birth weight. METHODS:We measured the levels of free thyroid hormones (FT3, FT4) and thyroid-stimulating hormone (TSH) in cord blood (n = 499) and maternal blood (n = 431) collected after delivery from mother-child pairs enrolled between February 2010 and June 2014 in the ENVIRONAGE birth cohort with catchment area in the province of Limburg, Belgium. RESULTS:An interquartile range (IQR) increment (8.2 ?g/m3) in third-trimester PM2.5 exposure was inversely associated with cord blood TSH levels (-11.6%; 95% CI: -21.8, -0.1) and the FT4/FT3 ratio (-62.7%; 95% CI: -91.6, -33.8). A 10th-90th percentile decrease in cord blood FT4 levels was associated with a 56 g decrease in mean birth weight (95% CI: -90, -23). Assuming causality, we estimated that cord blood FT4 mediated 21% (-19 g; 95% CI: -37, -1) of the estimated effect of an IQR increment in third-trimester PM2.5 exposure on birth weight. Third-trimester PM2.5 exposure was inversely but not significantly associated with maternal blood FT4 levels collected 1 day after delivery (-4.0%, 95% CI: -8.0, 0.2 for an IQR increment in third-trimester PM2.5). CONCLUSIONS:In our study population of normal healthy pregnancies, third-trimester exposure to PM2.5 air pollution was associated with differences in fetal thyroid hormone levels that may contribute to reduced birth weight. Additional research is needed to confirm our findings in other populations and to evaluate potential consequences later in life.

SUBMITTER: Janssen BG

PROVIDER: S-EPMC5382000 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Fetal Thyroid Function, Birth Weight, and <i>in Utero</i> Exposure to Fine Particle Air Pollution: A Birth Cohort Study.

Janssen Bram G BG Saenen Nelly D ND Roels Harry A HA Madhloum Narjes N Gyselaers Wilfried W Lefebvre Wouter W Penders Joris J Vanpoucke Charlotte C Vrijens Karen K Nawrot Tim S TS

Environmental health perspectives 20160913 4

<h4>Background</h4>Thyroid hormones are critical for fetal development and growth. Whether prenatal exposure to fine particle air pollution (≤ 2.5 μm; PM<sub>2.5</sub>) affects fetal thyroid function and what the impact is on birth weight in normal healthy pregnancies have not been studied yet.<h4>Objectives</h4>We studied the impact of third-trimester PM<sub>2.5</sub> exposure on fetal and maternal thyroid hormones and their mediating role on birth weight.<h4>Methods</h4>We measured the levels ...[more]

PMID: 27623605

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Project description:BackgroundStudies have identified relationships between air pollution and birth weight, but have been inconsistent in identifying individual pollutants inversely associated with birth weight or elucidating susceptibility of the fetus by trimester of exposure. We examined effects of prenatal ambient pollution exposure on average birth weight and risk of low birth weight in full-term births.MethodsWe estimated average ambient air pollutant concentrations throughout pregnancy in the neighborhoods of women who delivered term singleton live births between 1996 and 2006 in California. We adjusted effect estimates of air pollutants on birth weight for infant characteristics, maternal characteristics, neighborhood socioeconomic factors, and year and season of birth.Results3,545,177 singleton births had monitoring for at least one air pollutant within a 10 km radius of the tract or ZIP Code of the mother's residence. In multivariate models, pollutants were associated with decreased birth weight; -5.4 grams (95% confidence interval -6.8 g, -4.1 g) per ppm carbon monoxide, -9.0 g (-9.6 g, -8.4 g) per pphm nitrogen dioxide, -5.7 g (-6.6 g, -4.9 g) per pphm ozone, -7.7 g (-7.9 g, -6.6 g) per 10 microg/m3 particulate matter under 10 microm, -12.8 g (-14.3 g, -11.3 g) per 10 microg/m3 particulate matter under 2.5 microm, and -9.3 g (-10.7 g, -7.9 g) per 10 microg/m3 of coarse particulate matter. With the exception of carbon monoxide, estimates were largely unchanged after controlling for co-pollutants. Effect estimates for the third trimester largely reflect the results seen from full pregnancy exposure estimates; greater variation in results is seen in effect estimates specific to the first and second trimesters.ConclusionsThis study indicates that maternal exposure to ambient air pollution results in modestly lower infant birth weight. A small decline in birth weight is unlikely to have clinical relevance for individual infants, and there is debate about whether a small shift in the population distribution of birth weight has broader health implications. However, the ubiquity of air pollution exposures, the responsiveness of pollutant levels to regulation, and the fact that the highest pollution levels in California are lower than those regularly experienced in other countries suggest that precautionary efforts to reduce pollutants may be beneficial for infant health from a population perspective.

Project description:BackgroundAir pollution exposure during pregnancy might have trimester-specific effects on fetal growth.ObjectiveWe prospectively evaluated the associations of maternal air pollution exposure with fetal growth characteristics and adverse birth outcomes in 7,772 subjects in the Netherlands.MethodsParticulate matter with an aerodynamic diameter < 10 μm (PM10) and nitrogen dioxide (NO2) levels were estimated using dispersion modeling at the home address. Fetal head circumference, length, and weight were estimated in each trimester by ultrasound. Information on birth outcomes was obtained from medical records.ResultsIn cross-sectional analyses, NO2 levels were inversely associated with fetal femur length in the second and third trimester, and PM10 and NO2 levels both were associated with smaller fetal head circumference in the third trimester [-0.18 mm, 95% confidence interval (CI): -0.24, -0.12 mm; and -0.12 mm, 95% CI: -0.17, -0.06 mm per 1-μg/m3 increase in PM10 and NO2, respectively]. Average PM10 and NO2 levels during pregnancy were not associated with head circumference and length at birth or neonatally, but were inversely associated with birth weight (-3.6 g, 95% CI: -6.7, -0.4 g; and -3.4 g, 95% CI: -6.2, -0.6 g, respectively). Longitudinal analyses showed similar patterns for head circumference and weight, but no associations with length. The third and fourth quartiles of PM10 exposure were associated with preterm birth [odds ratio (OR) = 1.40, 95% CI: 1.03, 1.89; and OR = 1.32; 95% CI: 0.96, 1.79, relative to the first quartile]. The third quartile of PM10 exposure, but not the fourth, was associated with small size for gestational age at birth (SGA) (OR = 1.38; 95% CI: 1.00, 1.90). No consistent associations were observed for NO2 levels and adverse birth outcomes.ConclusionsResults suggest that maternal air pollution exposure is inversely associated with fetal growth during the second and third trimester and with weight at birth. PM10 exposure was positively associated with preterm birth and SGA.

Project description:ImportanceKnowledge of whether serious adverse pregnancy outcomes are associated with increasingly widespread effects of climate change in the US would be crucial for the obstetrical medical community and for women and families across the country.ObjectiveTo investigate prenatal exposure to fine particulate matter (PM2.5), ozone, and heat, and the association of these factors with preterm birth, low birth weight, and stillbirth.Evidence reviewThis systematic review involved a comprehensive search for primary literature in Cochrane Library, Cochrane Collaboration Registry of Controlled Trials, PubMed, ClinicalTrials.gov website, and MEDLINE. Qualifying primary research studies included human participants in US populations that were published in English between January 1, 2007, and April 30, 2019. Included articles analyzed the associations between air pollutants or heat and obstetrical outcomes. Comparative observational cohort studies and cross-sectional studies with comparators were included, without minimum sample size. Additional articles found through reference review were also considered. Articles analyzing other obstetrical outcomes, non-US populations, and reviews were excluded. Two reviewers independently determined study eligibility. The Arskey and O'Malley scoping review framework was used. Data extraction was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.FindingsOf the 1851 articles identified, 68 met the inclusion criteria. Overall, 32 798 152 births were analyzed, with a mean (SD) of 565 485 (783 278) births per study. A total of 57 studies (48 of 58 [84%] on air pollutants; 9 of 10 [90%] on heat) showed a significant association of air pollutant and heat exposure with birth outcomes. Positive associations were found across all US geographic regions. Exposure to PM2.5 or ozone was associated with increased risk of preterm birth in 19 of 24 studies (79%) and low birth weight in 25 of 29 studies (86%). The subpopulations at highest risk were persons with asthma and minority groups, especially black mothers. Accurate comparisons of risk were limited by differences in study design, exposure measurement, population demographics, and seasonality.Conclusions and relevanceThis review suggests that increasingly common environmental exposures exacerbated by climate change are significantly associated with serious adverse pregnancy outcomes across the US.

Project description:BackgroundA growing body of evidence has associated maternal exposure to air pollution with adverse effects on fetal growth; however, the existing literature is inconsistent.ObjectivesWe aimed to quantify the association between maternal exposure to particulate air pollution and term birth weight and low birth weight (LBW) across 14 centers from 9 countries, and to explore the influence of site characteristics and exposure assessment methods on between-center heterogeneity in this association.MethodsUsing a common analytical protocol, International Collaboration on Air Pollution and Pregnancy Outcomes (ICAPPO) centers generated effect estimates for term LBW and continuous birth weight associated with PM(10) and PM(2.5) (particulate matter ? 10 and 2.5 µm). We used meta-analysis to combine the estimates of effect across centers (~ 3 million births) and used meta-regression to evaluate the influence of center characteristics and exposure assessment methods on between-center heterogeneity in reported effect estimates.ResultsIn random-effects meta-analyses, term LBW was positively associated with a 10-?g/m3 increase in PM10 [odds ratio (OR) = 1.03; 95% CI: 1.01, 1.05] and PM(2.5) (OR = 1.10; 95% CI: 1.03, 1.18) exposure during the entire pregnancy, adjusted for maternal socioeconomic status. A 10-?g/m3 increase in PM(10) exposure was also negatively associated with term birth weight as a continuous outcome in the fully adjusted random-effects meta-analyses (-8.9 g; 95% CI: -13.2, -4.6 g). Meta-regressions revealed that centers with higher median PM(2.5) levels and PM(2.5):PM(10) ratios, and centers that used a temporal exposure assessment (compared with spatiotemporal), tended to report stronger associations.ConclusionMaternal exposure to particulate pollution was associated with LBW at term across study populations. We detected three site characteristics and aspects of exposure assessment methodology that appeared to contribute to the variation in associations reported by centers.

Dataset Information

Fetal Thyroid Function, Birth Weight, and in Utero Exposure to Fine Particle Air Pollution: A Birth Cohort Study.

Publications

Fetal Thyroid Function, Birth Weight, and <i>in Utero</i> Exposure to Fine Particle Air Pollution: A Birth Cohort Study.

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