Air pollution exposure during pregnancy, ultrasound measures of fetal growth, and adverse birth outcomes: a prospective cohort study

Abstract

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 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.

Results: In 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.

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.

Figure 1

Associations of PM₁₀ and NO₂ exposure with longitudinally measured fetal growth characteristics. Figures are based on spline regression models of longitudinally measured (A,D) head circumference (HC) growth, 17,726 observations; (B,E) length growth, n = 20,305 observations; and (C,F) weight growth, n = 20,395 observations, all expressed in SD scores (SDS), for each quartile (Q) of air pollution exposure during pregnancy (from conception until delivery) compared with the reference group (lowest quartile). A–C present associations for PM₁₀ exposure, and D–F present associations for NO₂ exposure. Head circumference was estimated by ultrasound in second and third trimester of pregnancy and measured neonatally. Fetal length was measured by ultrasound as crown–rump length in first trimester and femur length in second and third trimester and as body length neonatally. Weight was estimated by ultrasound in second and third trimester of pregnancy and measured at birth. p-Values are based on multivariate F-tests and reflect the difference between the spline of each air pollution exposure category compared with the reference category. Models are adjusted for maternal age, body mass index, height, parity, ethnicity, education, folic acid supplementation use, smoking, alcohol consumption, noise exposure, paternal height, and fetal sex.