Excuse my non-medical jargon, but i'll have a go with a laymans explanation of Crinone - please correct me where i'm wrong!

Crinone is progesterone, which your body (or your DW's!) should produce naturally in the phase after she ovulates. Some peoples bodies don't do this or need some help. I don't have progesterone issues, but my FS - (and some others do too), just give you some more support after a stim IVF cycle as they have mucked around with your body and hormones so much, that a bit more can't hurt!!
It's a gel/cream which you use in much the same way as a thrush treatment IYKWIM (if you don't - then ask DW). I got to use it for a full two weeks, and there is not enough room up there for all that stuff, and so it makes its way back out again - and it looks like cottage cheese crossed with god only knows what.
HEY, don't blame me - you asked!!!
But your DW may not need it - so maybe not a good idea to discuss with her until you know.