Optimal lead follicle size for human chorionic gonadotropin trigger in clomiphene citrate and intrauterine insemination cycles: an analysis of 1,676 treatment cycles

Our findings suggest that human chorionic gonadotropin administration at a lead follicle size of 21–22 mm is associated with higher odds of clinical pregnancy in clomiphene citrate–intrauterine insemination cycles.

VOLUME 115, ISSUE 4, P984-990


Kolbe L. Hancock, M.D., Nigel Pereira, M.D., Paul J. Christos, Dr.P.H., M.S., Allison C. Petrini, M.D., Jennifer Hughes, M.S.N., Pak H. Chung, M.D., Zev Rosenwaks, M.D.



To identify the optimal lead follicle size for hCG trigger in clomiphene citrate (CC)–intrauterine insemination (IUI) cycles.


Retrospective cohort study.


University-affiliated center.


Patients <40 years of age with ovulatory dysfunction or unexplained infertility undergoing their first CC-IUI cycle.


Ovulation induction, hCG trigger, and IUI.

Main Outcome Measure(s)

Clinical pregnancy rate (CPR) was the primary outcome and was plotted against lead follicle size in increments of 1 mm. Odds ratios with 95% confidence intervals for associations between lead follicle size and CPR were calculated from a multivariable logistic regression model. A receiver operating characteristic (ROC) curve was generated for CPR as a function of lead follicle size.


1,676 cycles were included. The overall CPR was 13.8% (232/1,676). There was no difference in baseline demographics or ovulation induction parameters of patients who did or did not conceive. The odds of clinical pregnancy were 2.3 and 2.2 times higher with lead follicle sizes of 21.1–22.0 mm and >22.0 mm, respectively, compared with the referent category of 19.1–20.0 mm. Lead follicle size was an independent predictor of CPR, even after accounting for confounders. A lead follicle size of 22.1 mm corresponded to a sensitivity and specificity of 80.1% and 90.4% for clinical pregnancy, respectively, with an area under the ROC curve of 0.89.


hCG administration at a lead follicle size of 21.1–22.0 mm is associated with higher odds of clinical pregnancy in patients undergoing their first CC-IUI cycles for ovulatory dysfunction or unexplained infertility.