Xiaoning Wang,1– 5,* Jiarong Tian,1– 5,* Liu Tian,1– 5 Xin Chen,1– 5 Zhenzhen Zhang,1– 5 Honglu Diao,1– 5,* Ying Zhang1– 5,* 

1Reproductive Medicine Center, Renmin Hospital, Hubei University of Medicine, Shiyan, Hubei Province, People’s Republic of China; 2Hubei Clinical Research Center for Reproductive Medicine, Renmin Hospital, Hubei University of Medicine, Shiyan, Hubei Province, People’s Republic of China; 3Shiyan Key Laboratory of Reproduction and Genetics, Renmin Hospital, Hubei University of Medicine, Shiyan, Hubei Province, People’s Republic of China; 4Biomedical Engineering College, Hubei University of Medicine, Shiyan, Hubei Province, People’s Republic of China; 5Hubei Key Laboratory of Embryonic Stem Cell Research, Hubei University of Medicine, Shiyan, Hubei Province, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Ying Zhang, Reproductive Medicine Center, Renmin Hospital, Hubei University of Medicine, 39 Chaoyang Middle Road, Shiyan, Hubei, 442000, People’s Republic of China, Tel +86 719 8637130, Email yingzhangivf@gmail.com

Purpose: Progestin-primed ovarian stimulation (PPOS) has been widely employed in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles. In recent years, letrozole (LE) combined with medroxyprogesterone acetate (MPA) has been used in this protocol to enhance ovarian response. This study compared the effects of a 5-day regimen with those of a 3-day regimen of letrozole within PPOS, focused on the follicular output rate (FORT) and blastocyst formation rates.
Patients and Methods: From January 2017 to January 2020, 1,754 infertility patients who received PPOS protocol were divided into two groups: 577 patients received 2.5 mg/day LE for 5 days (LE 5-day), and 1177 patients received the same dose of LE for 3 days (LE 3-day). Propensity score matching (1:1) balanced confounders, yielding 489 patients per group. The primary outcoms was the FORT. The rate of blastocyst formation was evaluated as the secondary outcome. A multivariable logistic regression analysis was performed to compare the disparity in the FORT between the two groups.
Results: After matching, the number of oocytes retrieved, number of mature oocytes, number of blastocysts, blastocyst formation rates, FORT, and clinical pregnancy rates were more favourable in the LE 3-day group than in the LE 5-day group (P < 0.05). In the multivariable linear regression model, after making adjustments for factors such as age, anti-Müllerian hormone (AMH), antral follicle count (AFC), body mass index (BMI), infertility type, and basal P, patients in the LE 3-day group exhibited an increase in the FOTR (β = 0.08, 95% confidence interval [CI] 0.02 to 0.14, P = 0.0082) and blastocyst formation rate (β = 0.23, 95% CI 0.17 to 0.29, P < 0.0001) compared to those in the LE 5-day group.
Conclusion: Compared with LE administration for 5 days, LE administration for 3 days may increase the FORT and the rate of blastocyst formation.

Keywords: in vitro fertilization, follicular output rate, letrozole, medroxyprogesterone acetate, ovarian stimulation