Fig. 1From: Association between pregnancy exposure to air pollution and birth weight in selected areas of NorwayDistribution of birth weight according to pregnancy exposure to NO2. Comparing groups with mean pregnancy exposures to NO2 below 20 μg/m3 and above or equal 20 μg/m3. The differences were significant (t-test) in both groups: overall analysis (A) 60 g (p < 0.0001); and analysis limited to nulliparous, nonsmoking mothers (B) 27 g (p = 0.047)Back to article page