Temporal variation in air pollution concentrations and preterm birth-a population based epidemiological study

Area of Science:

• Environmental Health
• Reproductive Epidemiology
• Perinatal Medicine

Background:

• Growing evidence links prenatal air pollution exposure to adverse birth outcomes.
• Recent studies present conflicting findings, necessitating further investigation.
• Vehicle exhaust and ozone are common urban air pollutants with potential health impacts.

Purpose of the Study:

• To evaluate the impact of ozone and nitrogen dioxide (NO2) exposure on gestational length.
• To assess the association between ozone and NO2 exposure and the risk of preterm delivery.
• To examine exposure effects across different gestational windows: first trimester, second trimester, and last week of gestation.

Main Methods:

• Utilized data from the Swedish Medical Birth Registry (1987-1995) for singleton births in Stockholm (n=115,588).
• Estimated daily average levels of NO2 and ozone using data from multiple monitoring stations.
• Employed linear regression for gestational length and logistic regression for preterm delivery risk, analyzing exposure during key gestational periods.

Main Results:

• Higher first-trimester ozone exposure correlated with shorter gestation and increased preterm delivery risk (OR 1.06 per 10 μg/m³).
• Second-trimester ozone exposure was linked to shorter gestation, but preterm delivery risk was not statistically significant.
• Ozone and NO2 exposure in the last week of gestation were associated with shorter gestation; NO2 also with preterm delivery.
• No significant associations were found between first or second-trimester NO2 exposure and the studied outcomes.
• First-trimester ozone's adverse effect was diminished in women conceiving in autumn, potentially due to higher vitamin D levels.

Conclusions:

• First-trimester ozone exposure poses a risk for shorter gestation and preterm birth.
• Later gestational exposure to ozone and NO2 also impacts gestation length and preterm birth risk.
• Seasonal variations in vitamin D may modulate the effects of early pregnancy air pollution exposure.