Baseline characteristics of pregnant workers participating in the study, in control and intervention groups at 16 weeks of pregnancy*
| Variable | Intervention group n=119 | Control group n=122 | P value |
| Demographics and general health | |||
| Age (years)† | 32 (5) | 33 (4) | 0.251 |
| Ethnic origin: Caucasian‡ | 102 (86%) | 110 (90%) | 0.288 |
| Educational level | |||
| University education or higher academic education | 69 (58%) | 68 (56%) | Ref |
| Higher professional education | 35 (29%) | 33 (27%) | 0.881 |
| Senior secondary vocational education | 15 (13%) | 21 (17%) | 0.354 |
| Body mass index (kg/m2) >25 | 22 (19%) | 14 (12%) | 0.172 |
| Health complaints/chronic illness before pregnancy | 10 (8%) | 10 (8%) | 0.954 |
| Medication prescribed by physician | 18 (15%) | 17 (14%) | 0.480 |
| Smoking during pregnancy | 0 | 2 (2%) | 0.498 |
| Drinking alcohol during pregnancy | 4 (3%) | 2 (2%) | 0.442 |
| Drugs: quit before pregnancy or earlier | 21 (18%) | 14 (12%) | 0.174 |
| Current pregnancy | |||
| With a fertility treatment | 9 (8%) | 9 (7%) | 0.985 |
| Twins or triplet | 3 (3%) | 4 (3%) | 1.000 |
| Parity ≥1 | 52 (44%) | 62 (51%) | 0.268 |
| Medical problems in former pregnancies? | 9/52 (17%) | 12/62 (19%) | 0.532 |
| Medical problems before current pregnancy? | 10 (8%) | 10 (8%) | 0.954 |
| Increase in complaints because of current pregnancy? | 37 (31%) | 39 (32%) | 0.884 |
| Work | |||
| Paid work from start of the pregnancy | 119 (100%) | 122 (100%) | 1.000 |
| Employment sector | |||
| Healthcare | 34 (29%) | 32 (26%) | Ref |
| Business services and research | 31 (26%) | 37 (30%) | 0.473 |
| Education, welfare and child care | 20 (17%) | 18 (15%) | 0.913 |
| Retail and hospitality and catering industry | 14 (12%) | 16 (13%) | 0.660 |
| Government and culture, recreation | 13 (11%) | 11 (9%) | 0.823 |
| Other (industry/NGOs/transport) | 6 (5%) | 8 (7%) | 0.756 |
| Number of employees in the company >50 | 81 (68%) | 85 (70%) | 0.715 |
| Self-employed§ | 6/105 (6%) | 8/117 (7%) | 0.615 |
| Commuting: travel distance >10 km | 71 (60%) | 73 (59%) | 0.980 |
| Travel time >1 hour/day (min/hour) | 50 (42%) | 49 (40%) | 0.768 |
| Private conditions | |||
| Sport | 66 (56%) | 57 (47%) | 0.195 |
| Times spent on hobby spending >5 hours/week | 9 (8%) | 9 (7%) | 0.985 |
| Children (living at home): Yes | 41 (35%) | 48 (39%) | 0.375 |
| Housework largely done by participant herself | 23 (19%) | 22 (18%) | 0.820 |
*Complete results in online supplemental file C.
†Mean (SD), all other variables mentioned as n (%).
‡Non-Caucasian includes: Turkish, Moroccan, Afro/American, Asian, Mixed and ‘other non-Western’.
§Based on second questionnaire (not in first questionnaire).
NGO, non-governmental organisation; NS, not significant; Ref, reference.