Table 3.
Overview of the number of study participants recruited in the first trimester (T1) by each of the paid advertisement methods stratified by study location.
| Advertisement Methods | Denmark | Netherlands | Poland | United Kingdom | Total |
| Total participants recruited by paid advertising n |
614 | 446 | 125 | 682 | 1867 |
| Total recruited in T1 n (% of total) |
299 (48.7%) | 47 (9.87%) | 28 (22.4%) | 68 (10.0%) | 442 (23.7%) |
| Website n T1/total by method (%) | 296/594 (49.8%) | 6/32 (18.8%) | 8/22 (36.4%) | 7/20 (35.0%) | 317/668 (47.5%)a |
| Email n T1/total by method (%) | 3/20 (15.0%) | 13/346 (3.8%) | 11/47 (23.4%) | 45/582 (7.7%) | 72/995 (7.2%) |
| Leaflet n T1/total by method (%) | - | 28/68 (41.2%) | 9/47 (19.1%) | 16/79 (20.3%) | 53/194 (27.3%) |
| Television n T1/total by method (%) | - | - | 0/9 (0.0%) | - | 0/9 (0.0%) |
| Paid Social Median T1/total by method (%) | - | - | - | 0/1 (0.0%) | 0/1 (0.0%) |
aPoisson regression (P<.001) identifies a significant difference in the proportion of first trimester study participants recruited between the website, email, and leaflet advertisement methods, driven by the high proportion of first trimester participants recruited by website advertisements.