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Table 1 Maternal characteristics by smoking status (unadjusted for sample weighting)

From: Prevalence of maternal smoking and environmental tobacco smoke exposure during pregnancy and impact on birth weight: retrospective study using Millennium Cohort

Maternal Characteristics Non-smoker, non ETS exposed (n = 8100) Non-smoker, ETS exposed (n = 2259) Active smoker (n = 6397) Excluded due to missing smoking data (n = 1541)
Maternal age at birth Mean (SD) 29.6 (5.6) 28.7 (5.5) 26.2 (6.0) 29.2 (5.8)
BMI Mean (SD) 24.0 (4.4) 24.0 (4.8) 23.2 (4.4) 23.8 (4.4)
Parity (previous live births) N (%) *     
None 3310 (42.2) 862 (40.1) 2838 (45.2) 496 (36.0)
1–2 3952 (50.4) 1083 (50.4) 2882 (45.9) 750 (54.5)
3 or more 572 (7.3) 203 (9.4) 553 (8.8) 131 (9.5)
Alcohol use in pregnancy N (%) 622 (7.7) 157 (7.0) 684 (10.7) 98 (6.6)
Ethnicity N (column %) *     
White 6501 (80.4) 1701 (75.4) 6058 (94.9) 1018 (68.2)
Asian 872 (10.8) 412 (18.3) 76 (1.2) 364 (24.4)
Black 438 (5.4) 43 (1.9) 117 (1.8) 64 (4.3)
Mixed or other 275 (3.4) 100 (4.4) 134 (2.1) 46 (3.1)
Education N (column %) *     
Degree 1942 (24.0) 320 (14.2) 351 (5.5) 247 (16.4)
Diploma or A level 1714 (21.2) 440 (19.5) 789 (12.4) 278 (18.5)
O levels 3090 (38.2) 938 (41.6) 3401 (53.3) 633 (42.1)
None of the above 1342 (16.6) 558 (24.7) 1840 (28.8) 347 (23.1)
Income (£) N (column %) *     
Less than 10,400 1482 (19.9) 424 (20.3) 2514 (42.2) 256 (20.9)
10,400 to 20,800 2194 (29.5) 835 (40.0) 2058 (34.5) 453 (37.0)
20,800 to 31,300 1723 (23.2) 469 (22.5) 822 (13.8) 240 (19.6)
Above 31,200 2035 (27.4) 358 (17.2) 568 (9.5) 277 (22.6)
  1. * where numbers in column do not add up to column total, this is due to missing data