In a severe case of anaphalaxis from an allergic or severe reaction to for example a bee bite, I personally would use benedryl. Then rush to vet or ER.
Benedryl is typically a benign drug but you should check with your vet about using it for a bred or pregnant bitch.
You would use it even though it appears on the list as something not to use on a pregnant bitch?
If you look at the times posted, that list was posted 4 minutes before my post. I had not seen it yet or prior.
My repro vet told me to use diphenhydramine in a serious emergency, pregnant or not. I did not repeat that because each vet has an opinion. My suggestion was for the OP to speak to their vet as they intend on doing.
Why are some of you looking for an argument for any reason?.......
Benadryl is safe for pregnant humans and safe for pregnant dogs. I use to give it on a human burn unit as if it were water. I gave it to pregnant women, infants, children,etc. It's a very safe drug. And yes, I've given it several times to pregnant bitches without any side effects.