Use of Clomiphene Citrate in minimal stimulation in vitro fertilization negatively impacts endometrial thickness: an argument for a freeze-all approach

OBJECTIVE: Minimal stimulation IVF is a treatment option that uses clomiphene citrate (CC). We sought to evaluate how CC impacts endometrial thickness during minimal stimulation IVF cycles. METHODS: We retrospectively analyzed a cohort of 230 cycles in 119 poor ovarian response patients. The IVF cycles were studied in three groups: 130 minimal stimulation cycles, 29 mild stimulation cycles, and 30 conventional high dose gonadotropin releasing hormone (GnRH) antagonist cycles. Thirty-three minimal stimulation IVF patients had 41 frozen embryo transfers (FET) which allowed us to study whether the CC effects were prolonged. RESULTS: Endometrial thickness in the minimal stimulation group was significantly lower than the mild and conventional stimulation groups (7.3±2.2mm versus 11.4±3.3mm versus 12.9±3.8mm, respectively, p<0.0001). In patients who underwent minimal stimulation IVF followed by FET, significantly thicker endometrial thickness was achieved during their FET cycles as compared to their minimal stimulation cycles (7.95±2.1mm versus 10.3±1.8mm, p<0.0001). CONCLUSION: We concluded that endometrial thickness is impacted during minimal stimulation IVF cycles. Since negative effects on endometrial thickness are not observed in the patients’ subsequent FET cycle, a freeze-all approach is justified to mitigate adverse endometrial effects of CC in minimal stimulation IVF cycles.