Air pollution and fetal growth- a study on ultrasound measures of Swedish children

Abstract

Background: Air pollution has been suggested to affect fetal growth. Most studies have relied on birth weight from birth records. Recent studies have been using ultrasound measures of fetal growth to assess air pollution effects. All of these studies have, however, been conducted in smaller study populations. Here, we have the opportunity to further advance our knowledge regarding the influence of air pollution exposures on fetal growth in a population based cohort of more than 48 000 pregnancies in women from Southern Sweden. The large study population allows us to perform sensitivity analyses. Methods: In this study we used outcome data from Swedish medical birth registers and an ultrasound database for around 55 000 pregnancies with two ultrasound measurements (one early in pregnancy and one late in pregnancy). We estimated exposures during different parts of pregnancies for all the pregnancies in the ultrasound database using geocoded residential adresses. The measures of air pollution exposure were obtained through dispersion modelling with input data from an emissions database (NOx) with high resolution (100m grids). We had knowledge from registers on potential confounders/interfering factors and effect modifiers (e.g.parity, sex, smoking, age and education of the mother). Results: In this large cohort of Swedish born children, we consistently estimated negative effects for NOx on most measures of fetal growth late in pregnancy. As an example, we show that our modelled NOx-exposures exhibit an effect on birth weight reducing birth weight by approximately 10g per 10 µg/m3 increment of NOx. This work was supported by FORMAS, The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.