Table 1 Baseline characteristics (n = 12,953)
Maternal characteristics | N | M (SD)/%a |
|---|---|---|
Maternal age, years | 12,953 | 31.0 (4.4) |
Pre-pregnancy BMI | ||
 Underweight (< 18.5) | 415 | 3.2 |
 Normal | 8548 | 66.0 |
 Overweight/obese (> 25) | 3827 | 29.9 |
 Missing | 163 | 1.3 |
Ethnicity | ||
 Dutch | 9,721 | 75.0 |
 Other western | 1,331 | 10.3 |
 Non-western | 1,893 | 14.6 |
 Missing | 8 | 0.1 |
Smoking during pregnancy | ||
 No | 11,101 | 85.7 |
 Yes | 1821 | 14.1 |
 Missing | 31 | 0.2 |
Educational level | ||
 Low | 1279 | 9.9 |
 Medium | 4531 | 35.0 |
 High | 6912 | 53.4 |
 Missing | 231 | 1.8 |
Parity | ||
 Nulliparous | 6243 | 48.2 |
 Multiparous | 6596 | 50.0 |
 Missing | 114 | 0.9 |
Infant characteristics | ||
 Birth weight, grams | 12,953 | 3485 (510.9) |
 Gestational age at birth, weeksb | 12,950 | 39.7 (1.6) |
Infant sex | ||
 Boys | 6589 | 50.9 |
 Girls | 6363 | 49.1 |
 Missing | 1 | 0.0 |