Evaluation of allylestrenol for clinical pregnancies in patients treated with assisted reproductive techniques: a retrospective, propensity score matched, observational study

Background: Allylestrenol is an oral progestogen being increasingly used for luteal phase support (LPS) inassisted reproductive techniques. However, evidence of the clinical efficacy of allylestrenol in LPS is lacking. Dydrogesterone is a representative drug used for LPS, the efficacy of which has been clinically confirmed. As such, we aimed to compare the effects of allylestrenol with the standard dydrogesterone on clinical pregnancy rates and pregnancy outcomes. Methods: : This retrospective study included 3375 assisted reproductive technique cycles using either allylestrenol or dydrogesterone between January 2015 and March 2020. Patients using either allylestrenol or dydrogesterone were matched in a 1:1 ratio using propensity scores. The primary outcomes were clinical pregnancy rate and pregnancy outcomes. Results: : No significant difference was found in the clinical pregnancy rate (54.4% vs. 53.7%, P = 0.787) and pregnancy outcomes (all P > 0.05) between allylestrenol and dydrogesterone. Compared with dydrogesterone, the use of allylestrenol significantly reduced the rate of biochemical pregnancies (6.4% vs. 11.8%, P < 0.001) and multiple gestation rate (16.8% vs. 26.3%, P = 0.001). Moreover, endometrial thickness, morphology, and blood flow were significantly improved by allylestrenol treatment (all P < 0.05). Conclusions: : Allylestrenol exhibited similar effects on clinical pregnancy rates and pregnancy outcomes as dydrogesterone. Moreover, allylestrenol had a more positive impact on biochemical pregnancy and endometrial receptivity.