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 μm; 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 μg/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.Citation:Janssen BG, Saenen ND, Roels HA, Madhloum N, Gyselaers W, Lefebvre W, Penders J, Vanpoucke C, Vrijens K, Nawrot TS. 2017. Fetal thyroid function, birth weight, and in utero exposure to fine particle air pollution: a birth cohort study. Environ Health Perspect 125:699–705; http://dx.doi.org/10.1289/EHP508

Exposure to Ambient Particulate Matter during Specific Gestational Periods Produces Adverse Obstetric Consequences in Mice

“…In utero exposure to , which has independently been shown to predispose children to these same later-life outcomes ( Johnson and Breslau 2000 ; Lewandowski et al 2013 ; Li et al 2014 ), could, in combination with small-for-gestational-age size, pose a synergistic increase in risk for these same obstetric consequences. A recent study by Janssen et al ( 2016 ) showed a link between human exposure to an increase in exposure levels in the third trimester and decreased thyroid stimulating hormone (TSH) levels and free thyroxine to triiodothyronine ratio (T 4 /T 3 ) in cord blood. The decrease in free T 4 in cord blood was linked to a 56-g decrease in average birth weight.…”

TSHβX1 Splice Variant Expression and D2 Thr92Ala Polymorphism Analysis in Pregnant Women with Thyroid Diseases

“…The thyroid diseases do not have a unique origin; genetic, endogenous, and environmental factors are involved [15,16]. It has been previously published that a relationship between obesity and hypothyroidism in which leptin levels intervene and in which TSH is directly responsible for weight gain [17].…”

Association of Prenatal and Perinatal Exposures to Particulate Matter With Changes in Hemoglobin A1c Levels in Children Aged 4 to 6 Years

“…Further proposed mechanisms include metabolic dysfunction induced through alterations in the gut microbiome [42][43][44][45] and thyroid dysfunction in pregnancy and in newborns. [46][47][48] Prenatal exposures to air pollution have been associated with sex-dependent effects on infant lung function, 49 childhood asthma, 50,51 neurodevelopment, 14,52,53 and metabolic outcomes, including childhood body composition, 15 neonatal birth weight, 54 and adult eating behavior as well as weight gain in animal studies. 55,56 The mechanisms leading to sex differences in the associations of fetal exposure to PM are not well understood.…”