Abstract
BackgroundThe effect of individual pollutants and the period(s) during pregnancy when pollutant levels are likely to have most impact on preterm birth is not clear. We evaluated the effect of prenatal exposure to six common urban air pollutants in the Sydney metropolitan area on preterm birth.MethodsWe obtained information on all births in metropolitan Sydney between January 1, 1998 and December 31, 2000. For each birth, exposure to each air pollutant was estimated for the first trimester, the three months preceding birth, the first month after the estimated date of conception and the month prior to delivery. Gestational age was analysed as a categorical variable in logistic regression models.ResultsThere were 123 840 singleton births in Sydney in 1998–2000 and 4.9% were preterm. Preterm birth was significantly associated with maternal age, maternal smoking, male infant, indigenous status and first pregnancy. Air pollutant levels in the month and three months preceding birth had no significant effect on preterm birth after adjusting for maternal and infant covariates. Ozone levels in the first trimester of pregnancy and spring months of conception and sulphur dioxide were associated with increased risks for preterm births. Nitrogen dioxide was associated with a decreased risk of preterm births.ConclusionWe found more protective than harmful associations between ambient air pollutants and preterm births with most associations non-significant. In view of these inconsistent associations, it is important to interpret the harmful effects with caution. If our results are confirmed by future studies then it will be imperative to reduce Sydney's already low air pollution levels even further.
Highlights
The effect of individual pollutants and the period(s) during pregnancy when pollutant levels are likely to have most impact on preterm birth is not clear
We examined this relationship in Sydney, Australia where ambient air pollution concentration is low compared with most cities where studies of the acute effects of air pollution have been conducted
After adjusting for meteorological, maternal and infant factors, preterm birth was significantly associated with maternal age, maternal smoking (OR = 1.62, 95%CI = 1.51–1.74), male sex of the child (OR = 1.22, 95%CI = 1.16–1.29), whether mother is an Aboriginal or Torres Strait Islander (OR = 1.60, 95%CI = 1.24–2.07) and first pregnancy (OR = 1.38, 95%CI = 1.30–1.45) (Table 1)
Summary
The effect of individual pollutants and the period(s) during pregnancy when pollutant levels are likely to have most impact on preterm birth is not clear. The review suggests that the effect of individual pollutants and the period(s) during pregnancy when pollutant levels are likely to have most impact on preterm birth is not clear. It is useful, to examine the impact of ambient air pollution and preterm birth in a variety of different sites to clarify the nature of the relationship. To examine the impact of ambient air pollution and preterm birth in a variety of different sites to clarify the nature of the relationship We examined this relationship in Sydney, Australia where ambient air pollution concentration is low compared with most cities where studies of the acute effects of air pollution have been conducted. Mean daily particulate concentrations in Sydney are lower than in any of the cities in the NMMAPS study in the USA [6]
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