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