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Table 1 Descriptive statisticsa for individual (Level-1) and DA (Level-2) covariates

From: The reduction of birth weight by fine particulate matter and its modification by maternal and neighbourhood-level factors: a multilevel analysis in British Columbia, Canada

Variables

Mean

Std. Dev.

Min-Max

PM 2.5 mean (SE)b

    

Absence/1st quintile

Presence/5th quintile

Level-1 (individual)

     

 Birth weight (grams)

3433.3

566.51

135 – 6475

7.30 (.016)

7.36 (.018)c,e

 Gestational age (weeks)

38.8

2.02

19 – 44

7.30 (.016)

7.30 (.017)f

 Maternal age (years)

29.8

5.60

11 – 55

7.10 (.022)

7.39 (.014)c

 Nulliparous

0.45

0.50

0 – 1

7.27 (.016)

7.34 (.016)c

 Gestational diabetes

0.06

0.25

0 – 1

7.29 (.016)

7.53 (.016)c

 Pre-existing diabetes

0.004

0.06

0 – 1

7.30 (.016)

7.34 (.034)

 Gestational hypertension

0.02

0.15

0 – 1

7.30 (.016)

7.44 (.019)c

 Poor prenatal care

0.09

0.29

0 – 1

7.28 (.016)

7.47 (.02)c

 Drug/Alcohol flag

0.02

0.15

0 – 1

7.31 (.016)

7.08 (.026)c

 Cigarettes/day

0.79

2.91

0 – 20

7.33 (.015)

7.02 (.023)c,g

 Fall/Winter season

0.48

0.50

0 – 1

7.29 (.016)

7.31 (.016)c

Level-2 (DA) variables

     

 SESi

-0.08

0.58

-2.22 – 1.18

7.82 (.027)

6.95 (.032)c,d

 Higher education

0.50

0.12

0 – 0.95

7.16 (.04)

7.53 (.022)c,d

 Immigrant density

0.16

0.19

0 – 0.86

6.75 (.023)

7.95 (.021)c,d

 Rural address

0.11

0.32

0 – 1

7.39 (.014)

6.59 (.061)c,d

 PM2.5 (μg/m3)

7.30

0.86

4.41 – 10.23

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  1. aValues shown are unstandardized, non-centered; Birth weights below 500 grams were included if their gestational age was > 19 weeks. Gestational age under 20 weeks were included if their birth weight was >499 grams. Poor prenatal care: having less than 4 prenatal care visits or was missing; Drug/Alcohol flag: indicates whether physician lists patient’s use of alcohol or drugs (prescription, nonprescription, illicit) as a risk factor in this pregnancy; Cigarettes/day: self-reported number of cigarettes smoked daily at 1st prenatal visit (excluding non-smokers, mean(sd) = 7.7 (5.41)); Fall/Winter season: birth month = September to February
  2. bRobust standard errors adjusted for 6338 DA clusters
  3. cSignificant difference at p < 0.05 using Wald tests
  4. d1st vs. 5th quintile
  5. eNormal birth weight vs. low birth weight
  6. fTerm birth vs. preterm birth
  7. gNon-smoker vs. current smoker