I dug up some info and am looking for more.

I found that a whitetail fetus grows more than 60% of it's size in the final trimester. This is timed to take winter stress off the doe and to coincide with the spring plant growth.
also... A fetus in a doe that was bred around Nov 15 will be less than 8 inches in length at the end of Feb, 100 days after conception.
Still fairly small heading into March.

I used the term delayed implantation, OOPS, that's black bears. Sorry, wrong term.

I still can't find the exact article. I didn't read it on the web. Probably not published on the web.