I don’t have the medical answer for this.
However, I had my progesterone checked several times during my protocol. I was on PIO before and the 2 weeks after transfer. It was checked 3 times while on PIO and it was around 50 each time.
I was starting to have a reaction to the PIO so I went to endometrim and oral progesterone and my level was over 100 after that (only checked once so far). They will be checking again next week.
Unfortunately I don’t have a PIO vs. only suppository (endometrim) comparrision number. I know there is a huge mix of what RE’s use…PIO, endometrim, crinone, oral, ect…and women seem to get pregnant on all of them.