Table 1.
Characteristics of the study population
| Value | ||
|---|---|---|
| Term birth | 1 515 338 (94·8%) | |
| Preterm birth | 84 209 (5·2%) | |
| 32 weeks and 0 days to 36 weeks and 6 days | 72 753 (4·5%) | |
| 28 weeks and 0 days to 31 weeks and 6 days | 8248 (0·5%) | |
| 26 weeks and 0 days to 27 weeks and 6 days | 2114 (0·1%) | |
| 24 weeks and 0 days to 25 weeks and 6 days | 1094 (0·1%) | |
| Gestational age, weeks | 39·5 (1·7) | |
| Birthweight, grams* | 3436 (547) | |
| Birthweight centile* | 49·3 (29·3) | |
| Small for gestational age* | 171 910 (10·7%) | |
| Sex† | ||
| Male | 819 886 (51·2%) | |
| Female | 779 654 (48·8%) | |
| Province of residence‡ | ||
| Drenthe | 39 344 (2·5%) | |
| Flevoland | 45 072 (2·8%) | |
| Friesland | 57 112 (3·6%) | |
| Gelderland | 181 830 (11·4%) | |
| Groningen | 49 643 (3·1%) | |
| Limburg | 82 613 (5·2%) | |
| Noord-Brabant | 221 212 (13·8%) | |
| Noord-Holland | 273 616 (17·1%) | |
| Overijssel | 109 762 (6·9%) | |
| Utrecht | 137 630 (8·6%) | |
| Zeeland | 31 278 (1·9%) | |
| Zuid-Holland | 369 084 (23·1%) | |
| Living in urban area‡ | 590 028 (36·9%) | |
| Neighbourhood socioeconomic status§ | ||
| Low (<20th percentile) | 301 611 (18·8%) | |
| Medium (20th–80th percentile) | 970 522 (60·7%) | |
| High (>80th percentile) | 319 809 (20·0%) | |
Data are n (%) or mean (SD).
*
Birthweight was missing for 391 individuals (0·02%).
†
Sex was unspecified for fewer than 10 individuals. According to National Institute for Public Health and the Environment policy, cells containing fewer than 10 individuals are censored.
‡
Postcode was missing for 1195 individuals (0·07%).
§
7605 cases (0·5%) could not be assigned to a Netherlands Institute for Social Research socioeconomic status category: 1195 due to missing postcode and 6410 because the Netherlands Institute for Social Research does not calculate neighbourhood socioeconomic status scores for postcodes with fewer than 100 households.