Recruitment through social media ads and videocalls: Cost, effectiveness, and lessons from the Experiences of Pregnancy Study

While participant recruitment via social media is increasingly used, its cost-effectiveness remains unclear for recruiting pregnancy cohorts, especially across social media platforms and in the context of increasing threats from robots and fraudulent participants. Accordingly, we report on the implementation and results of online recruitment for a longitudinal cohort study about mental health in pregnancy and postpartum (Experiences of Pregnancy (EoP) cohort). We describe: (1) the cost-effectiveness of Facebook, Instagram, Twitter/X, and Reddit for recruiting individuals in their first trimester (2) methods, experiences, and solutions for the prevention of bots and fraudulent participants (3) the representativeness of EoP compared to the United States (US) population and pregnancy cohorts recruited in person. Over three months (beginning June 2023), 574 eligible participants were recruited at a cost of US$6.19 per participant. Facebook and Instagram had the lowest cost per recruited participant. While EoP was not fully representative of the US population, it had similar representativeness to cohorts recruited in person. Overall, this study found that social media recruitment is a viable method for recruiting pregnant individuals in a time-efficient manner and at a reasonable cost but requires implementing a range of safeguards to counter robots and fraudulent participants from joining the study.