Recruitment strategies and challenges in a cohort study of pregnant women with a chronic medical condition in pregnancy

Abstract Background Recruiting pregnant women into longitudinal health research is challenging, particularly when studies involve low-prevalence chronic medical conditions not directly related to pregnancy. Comparative evidence on the effectiveness, cost, and representativeness of different recruitment strategies in this context remains limited. Therefore, this study aims to compare the effectiveness, sociodemographic characteristics and describe the associated costs of various strategies in recruiting pregnant women with psoriasis and matched controls in the Maternal Psoriasis and Infant Neurodevelopmental Outcomes (MaPINO) cohort study in New Zealand. Methods This cross-sectional analysis used recruitment data from the MaPINO longitudinal cohort of pregnant women with psoriasis and without psoriasis (unexposed group) in New Zealand (June 2022–December 2025). Nine recruitment strategies were implemented, including social media campaigns, healthcare database searches, clinic-based recruitment, referrals, word-of-mouth, advertising in a perinatal magazine, primary health care database search, and unpaid online advertisements. Screening outcomes, recruitment yield, cost, and participant characteristics were summarised using descriptive statistics. Associations between recruitment strategy and both ethnicity and socioeconomic deprivation were examined. Results A total of 604 individuals were screened, and 200 participants were enrolled (overall yield 33%), with a higher yield in the unexposed group than the psoriasis group (44.0% vs 26.7%). Social media campaigns recruited the largest proportion of participants ( n = 113,57%) and were the most cost-effective strategy (NZD$23 per recruit) but had lower yield (34.6%). Healthcare database searches using maternity hospital and national pharmaceutical collections were most effective for identifying pregnant women with psoriasis, yielding approximately 23% and improving recruitment of participants from the Māori (indigenous ethnicity in New Zealand) population. Clinic-based recruitment, referrals, unpaid online advertisements, and word-of-mouth achieved higher yields but contributed a small number of participants each. Recruitment through clinics was labour-intensive and costly per recruit (NZ$496). Advertisement in online perinatal magazine (NZD$2300) and searches at primary healthcare practices did not identify any potential participants for screening. Recruitment strategy was significantly associated with ethnicity ( p = 0.004) and socioeconomic deprivation ( p = 0.023) of recruited participants. Conclusion The MaPINO study experience highlights that recruiting participants into matched, longitudinal health research exploring chronic conditions during pregnancy, such as psoriasis, requires an integrated approach that combines social media advertising with the use of existing healthcare databases and healthcare providers to improve efficiency and feasibility in achieving recruitment targets.