[Thesis]. Manchester, UK: The University of Manchester; 2013.
Over the past decade there has been a substantial increase in evidence suggesting
an increased risk of adverse pregnancy outcomes from ambient air pollution exposure.
However, there is yet to be enough convincing evidence to confirm a causal link between
specific air pollutants and adverse pregnancy outcomes. The objective of this project
was to address the paucity of evidence from the UK on the risk from air pollution
in pregnancy. The research aim was to investigate the effects of ambient air pollution
on adverse pregnancy outcomes using retrospective birth outcome data from the ‘North
West Perinatal Survey Unit’ (NWPSU) during the period 2004 to 2008.In addition, primarily
to determine the most appropriate exposure estimation method, a prospective comparison
study (n=85) was performed to compare personal measurements of nitrogen oxides (NOx)
and specifically nitrogen dioxide (NO₂) with commonly used exposure estimation techniques.
This study informed two further studies which quantified the effects from air pollution
in pregnancy using a large retrospective cohort from the NWPSU. The first, investigated
the effects of maternal residential proximity to major roads on low birthweight (LBW),
small for gestational age (SGA) and preterm birth (PTB). The second, investigated
the effects of NOx, NO₂, carbon monoxide (CO) and particulate matter (PM₂.₅ and PM₁₀)
based on estimates from a novel spatio-temporal air pollution model and stationary
monitor sites on SGA, PTB and mean birth weight change. Linear and logistic regression
models were used to quantify the risk of adverse pregnancy outcomes from living in
close proximity to a major road and to specific ambient pollutants. Odds ratio (OR)
associations and mean birth weight change were calculated for each of the pollutants
with exposure averaged over the entire pregnancy and for specific pregnancy periods
to establish critical windows of exposure. Models were adjusted for maternal age,
ethnicity, parity, socio-economic status, birth season, body mass index and smoking.No
statistically significant associations were found between living <200m from a major
road and adverse pregnancy outcomes. Based on the spatio-temporal modelled air pollution
estimates, an increased risk of SGA was found in later pregnancy with NO₂ (OR=1.14,
95%CI= 1.00-1.30), CO (OR=1.21, 1.02-1.42), PM₂.₅ (OR=1.10, 1.00-1.21) and PM₁₀ (OR=1.12,
1.00-1.25). This study provides additional evidence that women exposed to high air
pollution concentrations in pregnancy are at an increased risk of an SGA birth, but
not for PTB. However, there was no evidence of an effect on SGA for exposures below
the current legal air quality limits.