Strengths and Limitations
To our knowledge, this is the first prospective study with the largest sample size (n=180) and randomized controlled design, investigating the effect of systemic oral progestin with or without LNG-IUS on fertility-preserving outcome in AEH patients. However, it is undeniable that several limitations in this study warrant further discussion. First, it was a single-center phase II study. The lack of double-blind design and placebo was also a weakness of the clinical trial. Moreover, all three treatment groups were combined with hysteroscopic evaluation and resection of endometrial lesion, which might conceal the difference in efficacy of the regimens. In addition, the follow-up time after complete response was relatively short. The rates of recurrence, pregnancy and live birth will be further analyzed after all patients have been followed up for two years. Finally, the rate of lost to follow-up in our study is relatively high (26.6% and 17.1% at 16 weeks and 32 weeks of treatment), which may reduce the accuracy of the results. Some patients eventually delayed or cancelled the hysteroscopy for various reasons, such as the COVID-19 quarantine, vaginitis, the conflict with their working hours, resulting in a high rate of lost follow-up.