Received January 02, 2023
Accepted May 22, 2023

We read the recently published article by Scheffer et al (2023) with great interest. This study is one of the few to evaluate the impact of serum progesterone level in luteal phase on pregnancy rates in fresh blastocyst transfer in antagonist cycles. The study also provides an insight into an optimal progesterone level on the day of blastocyst transfer with day-5 of progesterone supplementation (P4d5+) and gives a cut-off of ≥10 ng/ml to be associated with a significantly higher pregnancy rate. This could help us provide a more tailored progesterone supplementation for our patients, as it is well known that progesterone should be used with great caution and only when indicated (O’Brien, 2016). As much informative and thought-provoking as this article has been, we as readers would like to enquire the authors regarding some of our queries, that would help us in better understanding of the study. •