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Table 2 Unadjusted and adjusted associations between smoking during pregnancy and potential predictors.

From: Prevalence of smoking during pregnancy and associated risk factors among Canadian women: a national survey

  Sample size Smoking during pregnancy Unadjusted odds ratio Adjusted odds ratio
  N* N*(%) OR (95% CI)† OR (95% CI) †
Household income     
   < $30,000 1,031 230 (22.3) 10.12 (6.77-15.13) 1.73 (1.08-2.78)
   $30,000 to less than $60,000 1,853 242 (13.1) 5.31 (3.54-7.95) 1.86 (1.21-2.85)
   $60,000 to less than $100,000 1,940 111 (5.7) 2.14 (1.39-3.30) 1.09 (0.71-1.69)
   ≥ $100,000 1,212 33 (2.7) 1 1
Place of residence     
   Rural area 1,100 150 (13.6) 2.23 (1.78-2.80) 1.40 (1.04-1.87)
   Urban, population ≤ 499,999 2,283 310 (13.6) 2.22 (1.81-2.72) 1.42 (1.10-1.82)
   Urban, population ≥ 500,000 2,791 185 (6.6) 1 1
Immigrant     
   No 4,980 641 (12.9) 7.26 (4.79-11.00) 5.32 (3.32-8.51)
   Yes 1,407 28 (2.0) 1 1
Work during pregnancy     
   No 1,364 195 (14.3) 1.60 (1.34-1.91) 0.93 (0.72-1.20)
   Yes 5,028 475 (9.4) 1 1
Marital status     
   No partner 535 168 (31.4) 4.88 (3.97-6.01) 1.83 (1.33-2.53)
   Have a partner 5,860 501 (8.5) 1 1
Moms perceived health     
   Excellent/very good 4,645 396 (8.5) 1 1
   Good 1,419 208 (14.7) 1.84 (1.53-2.21) 1.17 (0.92-1.49)
   Poor/Fair 341 69 (20.2) 2.70 (2.03-3.60) 1.01 (0.67-1.51)
Alcohol drinking during pregnancy     
   No 5,713 576 (10.1) 1 1
   Yes 669 89 (13.3) 1.36 (1.06-1.74) 1.28 (0.93-1.77)
Health problems during pregnancy     
   No 4,837 485 (10.0) 1 1
   Yes 1,563 186 (11.9) 1.21 (1.01-1.46) 1.19 (0.95-1.50)
Reaction when discovered pregnancy     
   Very happy/happy 5,940 576 (9.7) 1 1
   Indifferent 265 58 (21.9) 2.63 (1.94-3.56) 1.09 (0.71-1.69)
   Very unhappy/Unhappy 180 36 (20.0) 2.35 (1.60-3.46) 0.93 (0.54-1.61)
Attended prenatal classes     
   No 4,306 528 (12.3) 1.89 (1.56-2.28) 1.43 (1.10-1.86)
   Yes 2,097 144 (6.9) 1 1
Support during pregnancy     
   None/Little of time 328 50 (15.2) 1.59 (1.15-2.21) 1.25 (0.82-1.91)
   Some of the time 502 52 (10.4) 1.03 (0.76-1.39) 0.97 (0.65-1.46)
   Most/All of time 5,555 567 (10.2) 1 1
Passive smoking during pregnancy     
   No 4,903 206 (4.2) 1 1
   Yes 1,499 466 (31.1) 10.28 (8.64-12.23) 5.31 (4.28-6.58)
Province‡     
   Eastern-Atlantic 379 51 (13.5) 1 1
   Eastern-Central 4,018 385 (9.6) 0.69 (0.57-0.83) 1.27 (0.85-1.89)
   Western-Prairies 1,220 159 (13.0) 0.97 (0.78-1.21) 1.15 (0.74-1.76)
   Western-British Columbia 755 64 (8.5) 0.60 (0.44-0.82) 1.24 (0.76-2.02)
   Northern territories 33 13 (39.4) 4.09 (3.32-5.05) 2.29 (0.73-7.14)
   Unadjusted Mean difference § (95% CI)†  
Years of education 6,349 -2.57 (-2.77--2.36) 0.84 (0.80-0.88)
Age at first pregnancy 6,332 -4.89 (-5.31--4.47) 0.93 (0.90-0.96)
Number of past pregnancies 6,397 0.62 (0.46-0.77) 1.08 (0.99-1.18)
Mother's age at selected birth 6,368 -2.88 (-3.36--2.39) 1.04 (1.01-1.07)
Weight gained during pregnancy 6,332 0.50 (-0.20-1.21) --
Number of stressful events 6,353 1.25 (1.07-1.42) 1.15 (1.08-1.23)
Number of prenatal visits 6,138 0.20 (-0.23-0.64) --
  1. * Sample size is estimated using normalized weights
  2. † 95% CI were calculated using bootstrapping technique
  3. ‡ Eastern Atlantic: Newfoundland & Labrador, Nova Scotia, Prince Edward Island & New Brunswick; Eastern Central: Quebec & Ontario; Western Prairies: Manitoba, Saskatchewan, & Alberta; Western British Columbia: British Columbia; and Northern Territories: Yukon Territory, Nunavut & Northwest Territories.
  4. § Represents the difference between the mean of smokers and non-smokers (Meansmokers - Meannon-smokers).