Hancock KL, Pereira N, Christos PJ, et al. - Researchers conducted this retrospective cohort study to identify the optimal lead follicle size for hCG trigger in clomiphene citrate (CC)–intrauterine insemination (IUI) cycles. Participants in the study were patients < 40 years of age with ovulatory dysfunction or unexplained infertility undergoing their first CC-IUI cycle. One thousand six hundred seventy-six cycles were involved. Data reported that the overall clinical pregnancy rate was 13.8%. No difference was found in baseline demographics or ovulation induction parameters of patients who did or did not conceive. In patients undergoing their first CC-IUI cycles for ovulatory dysfunction or unexplained infertility, hCG administration at a lead follicle size of 21.1–22.0 mm is correlated with greater chances of clinical pregnancy.