I have to say, that fetal development can only be appreciated by those who have been pregnant. Only a momma-to-be can understand the deep desire to know what is going on with the little bean growing and developing inside - both in a cosmic wonder sense, AND, in the sense that you worry every day that everything is going fine and that development is going well. If you have never been pregnant, it might not be interesting, or at the extreme, "gross", but perhaps only because it is different. We all fear the unknown / different / etc. That said, I think the comment should have not been made, and was insensitive and inappropriate.
Engagement rings? I stopped wearing mine about 3-4 years ago. Just never wanted to wear it anymore, I blamed it on not wanting to scratch it, etc. Then, I stopped wearing my wedding band. I blamed it on swollen pregnancy fingers. Last year, I filed for divorce. Looking back, I realized I was slowly shutting down in the marriage but couldn't admit it to myself, but this was my subconscious mind's way of starting to let go.
However, I think I am the exception. I think most women who no longer wear their rings have innocent reasons - they've outgrown the look, they are much older, the marriage is very solid and no need to keep wearing it, etc. Very few older women that I know still wear their engagement rings, because it represents a style from say 30-40 years ago and it just doesn't suit their style anymore.