Traffic pollution at the home address and pregnancy outcomes in Stockholm, Sweden.
BACKGROUND
For the past two decades, several studies have reported associations between elevated levels of ambient air pollution and adverse pregnancy outcomes, although with varying conclusions.


OBJECTIVE
To examine possible associations between the traffic pollution situation at the home address, for women who did not change address during pregnancy, and three types of pregnancy outcomes: spontaneous preterm delivery, children born small for gestational age (SGA) and pregnancy-induced hypertensive disorders.


METHODS
We used data for the Greater Stockholm Area from the Swedish Medical Birth Register to construct a cohort based on all pregnancies conceived between July 1997 and March 2006, n = 100 190. The pregnancy average nitrogen oxide, NOx, levels and annual mean daily vehicles at the home address were used as exposure variables. Mixed-model logistic regression was performed to assess any associations between exposure and outcome.


RESULTS
There was an association between elevated traffic pollution exposure during pregnancy and pregnancy-induced hypertensive disorders. A 10 µg/m(3) increase in the pregnancy average NOx level at the home address resulted in an OR of 1.17 (95% CI 1.10 to 1.26). The 2nd to 4th quartiles of NOx were all associated with an increased risk of SGA, but there was no difference in the risk estimate among the higher quartiles. There was a tendency of a higher risk of spontaneous preterm delivery in relation to higher levels of NOx. There was no evidence of an association between vehicle flow, the cruder indicator of traffic pollution, and the studied outcomes in this study.


CONCLUSIONS
In this large cohort, there was a fairly strong association between vehicle exhaust levels at the home address and pregnancy-induced hypertensive disorders, after adjustment for important risk factors.
Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden.
David
D
Olsson
Department of Clinical Sciences, Obstetrics and Gynecology, Umeå University, Umeå, Sweden.
Ingrid
I
Mogren
Environment and Health Administration, Stockholm, Sweden.
Kristina
K
Eneroth
Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden.
Bertil
B
Forsberg
D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology*; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D016015:Logistic Models; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D018986:Motor Vehicles; D009589:Nitrogen Oxides / Q000009:adverse effects / Q000032:analysis; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000209:etiology*; D012307:Risk Factors; D013548:Sweden; D001335:Vehicle Emissions / Q000032:analysis
D000393:Air Pollutants; D009589:Nitrogen Oxides; D001335:Vehicle Emissions
EPIDEMIOLOGY; PUBLIC HEALTH