Academic journal article Environmental Health Perspectives

Air Pollution Exposure during Pregnancy, Ultrasound Measures of Fetal Growth, and Adverse Birth Outcomes: A Prospective Cohort Study

Academic journal article Environmental Health Perspectives

Air Pollution Exposure during Pregnancy, Ultrasound Measures of Fetal Growth, and Adverse Birth Outcomes: A Prospective Cohort Study

Article excerpt

BACKGROUND: Air pollution exposure during pregnancy might have trimester-specific effects on fetal growth.

OBJECTIVE: We prospectively evaluated the associations of maternal air pollution exposure with fetal growth characteristics and adverse birth outcomes in 7,772 subjects in the Netherlands.

METHODS: Particulate matter with an aerodynamic diameter < 10 um (PM10) and nitrogen dioxide [NO.sub.2] 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.

RESULTS: In cross-sectional analyses, [NO.sub.2] levels were inversely associated with fetal femur length in the second and third trimester, and PMjo and [NO.sub.2] 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-ug/m3 increase in PM(0 and [NO.sub.2], respectively]. Average PMI0 and [NO.sub.2] 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 [PM.sub.10] 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 PMI0 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 [NO.sub.2] levels and adverse birth outcomes.

CONCLUSIONS: Results 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.

Key WORDS: air pollution, birth weight, dispersion modeling, fetal growth, intrauterine growth restriction, nitrogen dioxide, particulate matter, pregnancy, preterm birth. Environ Health Perspect 120:150-156(2012). http://dx.doi.org/10.1289/ehp.10033l6COnline26August2011]

Maternal exposure to air pollution during pregnancy has been suggested to be associated with increased risks of adverse birth outcomes such as low birth weight, intrauterine growth restriction, and preterm birth (Ritz and Wilhelm 2008). Thus far, results are not consistent: Reported associations (or absence thereof) for specific air pollutants, exposure periods, and birth outcomes have differed between studies (Bonzini et al. 2010; Shah and Balkhair 2011). Most previous studies defined fetal growth using measures at birth, such as weight, length, and head circumference (Choi et al. 2006; Hansen et al. 2007; Jedrychowski et al. 2004; Salam et al. 2005). However, because impaired growth during early pregnancy may be compensated for in the remaining intrauterine life, the eventual measures at birth can represent both normal and abnormal fetal growth and development. To provide insight into the specific effects of maternal air pollution exposure and to identify critical windows of exposure, it is of interest to assess fetal growth in different periods of pregnancy rather than only at birth. A small number of studies have examined the impact of air pollution exposure on fetal growth using ultrasound measurements during pregnancy as direct estimates of growth (Aguilera et al 201G; Hansen et al. 2008; Slama et al. 2009). These studies were based on small numbers, did not report measurements in each trimester of pregnancy, or were not able to consider the spatiotermporal variation in air pollution exposure.

Wc investigated associations of particulate matter with an aerodynamic diameter < 10 (am [PM. …

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