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Table 1 Background characteristics of mothers to children born 2000–2003, the Danish National Birth Cohort, Denmark

From: Maternal pre-pregnancy body mass index, smoking in pregnancy, and alcohol intake in pregnancy in relation to pubertal timing in the children

Background Characteristics Boys (n = 23,003)
No. (%)
Girls (n = 19,846)
No. (%)
Missing
No. (%)
Pre-pregnancy BMI    614 (1.4)
 < 18.5 kg/m2 984 (4.3) 833 (4.3)  
 18.5–24.9 kg/m2 15,287 (67.4) 13,119 (67.1)  
 25.0–29.9 kg/m2 4437 (19.6) 3875 (19.8)  
 30.0+ kg/m2 1979 (8.7) 1721 (8.8)  
Smoking in pregnancy    41 (0.1)
 Non-smoker 17,382 (75.6) 14,963 (75.5)  
 Stopped smoking 2194 (9.5) 1933 (9.7)  
 1–9 daily cigarettes 1921 (8.4) 1667 (8.4)  
 10–14 daily cigarettes 949 (4.1) 768 (3.9)  
 15+ daily cigarettes 532 (2.3) 499 (2.5)  
Alcohol in pregnancy    16 (0.0)
 Abstainer 12,480 (54.3) 11,036 (55.6)  
 < 1 weekly units 7199 (31.3) 6026 (30.4)  
 1–3 weekly units 2787 (12.1) 2362 (11.9)  
 > 3 weekly units 527 (2.3) 416 (2.1)  
Maternal age of menarche    373 (0.9)
 Earlier than peers 5638 (24.7) 5036 (25.6)  
 Same time as peers 13,359 (58.6) 11,278 (57.4)  
 Later than peers 3819 (16.7) 3346 (17.0)  
Highest social class of parents    89 (0.2)
 High grade professional 5565 (24.2) 4718 (23.8)  
 Low grade professional 7271 (31.7) 6440 (32.5)  
 Skilled worker 6499 (28.3) 5552 (28.0)  
 Unskilled worker 3060 (13.3) 2620 (13.2)  
 Student 442 (1.9) 379 (1.9)  
 Economically inactive 115 (0.5) 99 (0.5)  
Parity    1 (0.0)
 First child 11,146 (48.5) 9751 (49.1)  
 Second child or more 11,856 (51.5) 10,095 (50.9)  
Maternal age at delivery, years, mean (sd) 30.5 (4.2) 30.4 (4.2) 23 (0.1)
Childhood BMI at 7 years, mean (sd) 15.7 (1.7) 15.6 (1.8) 17,008 (39.7)
  1. BMI Body Mass Index, sd standard deviation