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Table 2 Characteristics of mothers and newborns delivered at Beijing Haidian Maternal and Child Health Hospital, 2006–2010

From: Ambient air pollution and adverse birth outcomes: a natural experiment study

Characteristics Term sample (N = 47,671) Preterm sample (N = 3,203)
  Male (N = 24,843) Female (N = 22,600) Male (N = 1,784) Female (N = 1,387)
Birth weight (grams) 3453.7 3331.4 2581.4 2477.2
(Std dev) (415.1) (402.8) (523.9) (513.6)
Birth year %     
2006 6.63 6.25 6.00 6.49
2007 23.81 23.99 21.69 23.22
2008 23.60 23.81 27.19 24.44
2009 24.97 24.62 26.23 25.67
2010 21.00 21.33 18.89 20.19
Household registration (Huji) %    
Urban Huji of Beijing 54.82 55.89 48.71 49.53
Rural Huji of Beijing 1.82 1.84 1.85 1.95
Other province, urban 27.33 27.44 26.51 26.03
Other state, rural 15.91 14.73 22.65 22.42
Missing 0.12 0.11 0.28 0.07
Maternal age at delivery (years)    
Mean (STD) 29.2 (3.7) 29.2 (3.6) 29.3 (4.2) 29.3 (4.3)
Parity %     
1 87.58 89.99 80.55 84.21
2+ 12.41 9.98 19.34 15.65
Missing 0.02 0.03 0.11 0.14