Congrats on your pregnancy! I am planning on TTC this summer and am so excited just thinking about it
My dd will be the same age as your ds if all goes as planned.
From what I researched I understand the cream should be labeled as "U.S.P. Natural Progesterone" to be effective. It all comes from wild yam but those that are not labeled USP have not been synthesized into usable human progesterone and will do little for you. As for the warning label that is just a legal thing IMO and I take it with a grain of salt in most cases.
I've been using topical progesterone cream for over 5 years because of estrogen dominance and perimenopausal symptoms. I continued through the first trimester of my pregnancy and started back with it as soon as my period returned 6 weeks postpartum. I use it every month from day 14-26 of my cycle, doing so keeps my previously strange cycle regular and my once horrible PMS to a minimum.
Canyon River Naturals makes the stuff I use: http://www.premugest.com/info.htm
This progesterone is in a cream made from emu oil which has molecules small enough to penetrate the skin. I could feel it's effects immediately when I rubbed it on the first time so I knew I'd found a good product! The only thing I don't like is the scent which is very sweet smelling, but I am very scent sensitive so it may just be me.