You are how you recruit: a cohort and randomized controlled trial of recruitment strategies

BACKGROUND: Recruitment is a challenge in developing population-representative pregnancy and birth cohorts. METHODS: We developed a collaborative recruitment infrastructure (CRI) to recruit pregnant women for 4 pregnancy cohorts using: faxes from obstetrical offices, in-clinic recruiters, university and funder-driven free-media events, paid-media, and attendance at relevant tradeshows. Recruitment rates and demographic differences were compared between recruitment methods. RESULTS: We received 5008 referrals over 40 months. Compared to fax, free-media referrals were 13 times more likely to be recruited (OR 13.0, 95% CI 4.2, 40.4: p 0.05). CONCLUSION: Recruitment methods result in different recruitment rates and participant demographics. A variety of methods are required to recruit a generalizable sample.