Thank you Megan for clarifying. I don't really wish to get into detail about my medical issues but suffice to say that using progesterone cream is the supplement of choice for both my medical condition and my practitioner. I generally like to assume, unless otherwise indicated, that women posting at mdc about their medical needs know their diagnosis.
I did, by the way, ask my naturopath today why those in her line of practice prefer cream to suppositories and why progesterone over clomid, which I used prior to the first pregnancy for the same purpose. That was at a time when I was seeing a reproductive endocrinologist for supposedly medically mystifying infertility that turned out to be very easily solved with progesterone and increased thyroid meds. (could have saved thousands of $$ if I had stuck with the naturopath in the first place) Anyway, she said the means of entering the body is still topically with both creams and suppositories and there is no guarantee that either is getting any more or less hormone to the body.
And, to answer the question that started this thread, my doc said that women who are trying to concieve and have been identified with a problem with low progesterone can take the hormone while they are ttc and then they can and should continue to do so for the first trimester, using the same product at the same levels. It is not wise to start anew after pregnancy with progesterone, she said, nor is it wise to change the dose. That is probably what the pharmacist meant.
I did a few google searches and found this article
to be particularly interesting.