Characteristics of pregnant women (n=6302) enrolled in a prospective prenatally recruited birth cohort, 2002–2006
| Variables | n | % |
| Individual characteristics | ||
| Age at enrolment in study | ||
| <25 years | 1066 | 17% |
| 25–30 years | 1690 | 29% |
| 30–35 years | 2530 | 40% |
| ≥35 years | 1016 | 16% |
| Educational level | ||
| Low | 1355 | 22% |
| Mid-low | 2016 | 32% |
| Mid-high | 1277 | 20% |
| High | 1654 | 26% |
| Country of origin | ||
| Netherlands | 3412 | 54% |
| Surinam and Dutch Antilles | 658 | 10% |
| Morocco and Turkey | 752 | 12% |
| Other | 1480 | 24% |
| Parity | ||
| First child | 3689 | 58% |
| Second child and higher | 2613 | 42% |
| Smoker during mid-pregnancy | 827 | 13% |
| Alcohol use during mid-pregnancy | 2046 | 32% |
| Occupational characteristics | ||
| Paid employment | 4556 | 72% |
| Skill level | ||
| Elementary education | 134 | 3% |
| Lower secondary education | 975 | 22% |
| Higher secondary education | 1397 | 31% |
| Tertiary education | 1283 | 29% |
| Academic education | 643 | 15% |
| Outcome measures | ||
| Live birth | 6282 | 99.7% |
| Preterm birth | ||
| <34 weeks | 78 | 1.2% |
| <37 weeks | 346 | 5.5% |
| Birth weight (n=6201) | ||
| <2500 g | 285 | 5% |
| 2500–3000 g | 926 | 15% |
| 3000–3500 g | 2175 | 35% |
| 3500+ g | 2817 | 45% |
| Time to pregnancy (n=3719) | ||
| ≤6 months | 2796 | 75% |
| 6–12 months | 536 | 15% |
| >12 months | 387 | 10% |