No suggestions regarding the parenting side from me. For the rest of it though...

The best thing to do would be to take some time to talk to her about exactly what it is she wants, what you want, and try to find the common ground you can both be happy with. There are some very good surveys posted on the site regarding hard limits/interests that you can both fill out and then discuss things.

I think I would recommend against trying to jump straight into pain play with a pregnant wife. Even experienced people make mistakes, and trying to jump too quickly when the life of your child could hang in the balance seems unwise.

But you have been married for 8 years, so what's a few more months of waiting? Take the next few months and figure out exactly what you both will or won't like (or think you will or won't like) talk a lot, figure out limits and terms, and stick to light play. Ramp it up when and where and how you can once the child arrives.

.02