Description of the sample and variables of interest
| N* | % | |
|---|---|---|
| Cohort | ||
| Asturias | 416 | 18.4 |
| Gipuzkoa | 545 | 24.1 |
| Sabadell | 591 | 26.1 |
| Valencia | 711 | 31.4 |
| Age | ||
| ≤ 24 | 154 | 6.8 |
| 25–29 | 717 | 31.7 |
| 30–34 | 973 | 43.0 |
| ≥ 35 | 418 | 18.5 |
| Social class | ||
| I–II (more affluent) | 492 | 21.8 |
| III | 584 | 25.8 |
| IV–V (less affluent) | 1186 | 52.4 |
| Level of education | ||
| Primary or no education | 547 | 24.2 |
| Secondary | 936 | 41.4 |
| University | 776 | 34.4 |
| BMI (pre-pregnancy) | ||
| <18.5 | 100 | 4.4 |
| 18.5–25 | 1568 | 69.3 |
| 25–30 | 420 | 18.6 |
| ≥ 30 | 175 | 7.7 |
| Previous parity | 957 | 43.1 |
| Birth in Europe | 2130 | 94.3 |
| Reported having smoked in their life | ||
| No | 879 | 38.8 |
| Occasional | 146 | 6.5 |
| Regular | 1238 | 54.7 |
| Reported smoking at the start of pregnancy | ||
| No | 1529 | 67.6 |
| Occasional | 28 | 1.2 |
| Regular | 706 | 31.2 |
| Reported smoking at the first trimester of pregnancy | ||
| No | 1813 | 80.3 |
| Occasional | 35 | 1.6 |
| Regular | 410 | 18.2 |
| Reported smoking at the third trimester of pregnancy | ||
| No | 1845 | 81.5 |
| Occasional | 37 | 1.6 |
| Regular | 381 | 16.8 |
| Year of urine sampling | ||
| 2004 | 321 | 14.2 |
| 2005 | 857 | 37.9 |
| 2006 | 466 | 20.6 |
| 2007 | 470 | 20.8 |
| 2004 | 149 | 6.6 |
| Cigarettes/day at the third trimester of pregnancy | ||
| 0 | 1845 | 81.5 |
| Occasional | 37 | 1.6 |
| 1–4 | 149 | 6.6 |
| 5–9 | 141 | 6.2 |
| ≥ 10 | 91 | 4.0 |
| Exposed to SHS in non-smoking women†: | ||
| At home (partner or others) | 479 | 26.0 |
| At work | 186 | 10.1 |
| Elsewhere in leisure time‡ | 715 | 38.8 |
| Number of sources of exposure to SHS§ | ||
| 0 | 798 | 43.5 |
| 1 | 735 | 40.0 |
| 2 | 271 | 14.8 |
| 3 | 32 | 1.7 |
| Cotinine (ng/ml) all the women | ||
| < 50 | 1773 | 78.3 |
| 50–99 | 31 | 1.4 |
| 100–199 | 19 | 0.8 |
| 200–499 | 52 | 2.3 |
| 500–999 | 70 | 3.1 |
| ≥ 1000 | 318 | 14.1 |
*The numbers and rates that do not match the total are due to missing data.
†Percentages calculated including non-exposed women.
‡Other homes or public places, for example, pubs or restaurants.
§Work, home and elsewhere in leisure time among non-smokers.
BMI, body mass index; SHS, second-hand smoke.