Mild Ovarian Stimulation Using the Aromatase Inhibitor Letrozole (LTZ) is a Good Stimulation Protocol for to Obtain Euploid Blastocysts for Advanced Maternal Age Women

Purpose: Mild Ovarian Stimulation (MOS) is an effective form of Assisted Reproductive Technology (ART) for Advanced Maternal Age (AMA) women. Taking either Clomiphene (CC) or Letrozole (LTZ) with MOS reduces the amount of gonadotropin that must be used. It has remained uncertain, however, whether LTZ or CC is more effective in combination with MOS. Therefore, we evaluated the choice of combination of either CC or LTZ with MOS and quantified the obtainment of euploid blastocysts for AMA women. Methods: This retrospective study was conducted between January 2020 and April 2021. In this study, we stimulated 286 women with MOS, 153 of these women used CC (CC group) and 133 were given LTZ (LTZ group). All women took either 100 mg of CC or 5 mg of LTZ daily for 7 days between MC 3 and MC 9, and 225 IU of recombinant-FSH were administered on MC 3, MC 5, MC 7, and MC 9. The euploid rates were compared between these two groups. Among them, the women who were ≥ 40 years old were divided into two groups, the CC-O40 group (n = 61) and LTZ-O40 group (n = 54), and the euploid rates were evaluated. Results: For AMA women, the blastocyst formation rate in the LTZ-O40 group (58.5%) was significantly higher than that in the CC-O40 group (46.6%, p < 0.05). The euploid rate in the LTZ group was 53.4%, which was significantly higher than that in the CC group (38.0%, p < 0.05). The AMA euploid rate in the LTZ-O40 group was 40.5%, which also was significantly higher than that in the CC-O40 group (16.7%, p < 0.05). Conclusions: For AMA women, a regimen of LTZ combined with MOS is the most effective ovarian stimulation method for obtaining euploid blastocysts.