Has anyone's bitches vulva gone back down to normal size after mating and had been pregnant?  I'm sure with my bitch it's the size it was before mating
   Thank you

Yes -in fact I posted about it here last year as I didn't think she could be pregnant. That bitch was pregnant and had a good sized litter.

No.   And of any of 'the signs' this is the one thing I tend to go by, with mine.   Obviously they go back from how they are when in full season, but not quite to the 'as before' size.   But then I had one who went back to a blood-coloured discharge through her final week, which wasn't usual with mine after being mated.   She had an uneventful pregnancy and 9 really good puppies - so good we kept 3.

Yes,pretty much every bitch we have here goes back to normal size whether mated or not and we have never had a bitch miss.