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Table 1 Descriptive statistics# for individual (Level-1) and DA (Level-2) covariates on term birth weight

From: Air pollution, neighbourhood and maternal-level factors modify the effect of smoking on birth weight: a multilevel analysis in British Columbia, Canada

Variable Mean (sd) Min-max
Level-1 (individual)
Maternal age 29.8 (5.60) 11 – 55
Nulliparous 0.45 (0.50) 0 – 1
Drug/Alcohol flag 0.02 (0.15) 0 – 1
Cigarettes/day 0.79 (2.91) 0 – 20
Fall/Winter season 0.48 (0.50) 0 – 1
Level-2 (DA) Variables
SESi -0.08 (0.58) -2.22 – 1.18
Education 0.50 (0.12) 0 – 0.95
Immigrant density 0.16 (0.19) 0 – 0.86
PM2.5 7.30 (0.86) 4.41 – 10.23
Rural address 0.11 (0.32) 0 – 1
  1. # values shown are unstandardized, non-centered; Nulliparous: patient has never delivered a baby of at least 500 g birth weight or at least 20 weeks gestation in a previous pregnancy; Drug or Alcohol Flag: physician indicated use of drugs (prescription, non-prescription, illicit) or alcohol as risk factor in pregnancy; Cigarettes/day: number of cigarettes smoked daily at 1st prenatal visit (self-reported); Fall/Winter Season: month or birth between September to February; SESi: socioeconomic status index; Education: proportion of population over 15 with any post-secondary education (trade, college, university); Immigrant Density: proportion of the population identified as immigrant status from continental Asia; PM2.5: Particulate Matter less than 2.5 μm; Rural: those having a rural residential address