Strengths and Limitation
Firstly, it was the first study to make direct comparisons of ultra-long, long, antagonist and short protocols on IVF/ICSI outcomes. Secondly, we ascertained ultra-long protocol was a better choice in fresh ET cycles for severer adenomyosis, and ultra-long or long protocols were both considerable for milder adenomyosis. Thirdly, we observed that antagonist and short protocols could decrease time and economic cost, and the poor pregnancy outcomes in fresh ET cycles could be reversed by whole embryo frozen and FET strategy.
The limitation of the study was the possible bias of a retrospective study, however, we developed strict inclusion and exclusion criteria to minimize the bias. The embryologists assessing embryo quality were independent of the study and avoided relevant bias. The differences of baseline parameters existed, therefore, we carried out logistic regression to adjust relevant parameters and increased the reliability of results. Of course, prospective studies were needed to verify the conclusions.