We conducted a parallel non-blinded randomized trial to assess whether offering home pregnancy tests (HPT) to preconception cohort study participants influenced cohort retention or pregnancy detection. Pregnancy Study Online (PRESTO) participants were female, aged 21-45 years, attempting pregnancy, and not using fertility treatment. At enrollment (2017-2018), 1,493 participants with ≤6 cycles of attempt time were randomized with 50% probability to receive Clearblue visual HPTs plus the standard protocol (N=720) or the standard protocol (N=773). Women completed bimonthly questionnaires for 12 months or until conception, whichever came first. In intent-to-treat analyses, retention (≥1 follow-ups) was higher in the HPT arm (N=598; 83%) than the standard protocol arm (N=535; 69%) (mean difference=15%, 95% CI: 10%, 19%). Mean time at first pregnancy testing was identical in both arms (2 days before expected menses), as was mean gestational weeks at first positive pregnancy test (4 weeks). Conception was reported by 78% in the HPT arm and 75% in the standard protocol arm. Spontaneous abortion was reported by 21% in the HPT arm (mean gestational weeks=7) and 21% in the standard protocol arm (mean gestational weeks=6). Randomization of HPTs was associated with greater cohort retention, but had little impact on incidence or timing of pregnancy detection.
