Sonographic determination of a possible adverse effect of clomiphene citrate on endometrial growth

We recently demonstrated, using transvaginal sonography, thatconception cycles in in-vitro fertilization (IVF) are associatedwith a significantly thicker endometrium at mid-cycle than non-conceptioncycles, suggesting that endometrial growth may influence implantation.In the present study, to examine whether the type of stimulationprotocol affects endometrial development, we compared the sonographicappearance of the endometrium in 22 patients randomized to receiveclomiphene citrate and human menopausal gonadotrophin (CC/HMG)and in 19 who received HMG alone. A significantly thicker endometriumwas observed in the HMG patients compared to the CC/HMG group(P < 0.005) throughout the follicular phase of the cycle,although serum concentrations of oestradiol (E₂) did not differin the two groups. Twenty-three patients (13 in the HMG groupand 10 in the CC/HMG group) had previous IVF cycles with CC/HMGstimulation in which endometrial thickness was measured. A thinendometrium recurred with subsequent CC/HMG cycles while increasedgrowth occurred with HMG only compared to previous CC/HMG cycles.Therefore, ultrasound examination of the endometrium in thisstudy demonstrated that CC results in a thinner endometriumthan HMG alone. We believe these findings may be of importancein improving pregnancy rates in IVF and possibly in other infertilitytherapy which involves the use of clomiphene citrate.