It's not just while your wife is pregnant that you have to take into consideration, imagine when baby is here, they need an unbelievable amount of equipment! It won't be much fun for either of you having to carry all baby's stuff up and down the stairs, car seats, and travel systems!
I would of thought that it will be a big hassle for your wife everytime she wants to take baby out for a walk, as she'll have to struggle down all those stairs with a buggy or pram, then go back and get baby, and when she gets home she'll have to disturb baby by getting him or her out the pram and carrying him/her up seperately (I assume).
I would think it will make it more difficult than living on a ground floor, or having a lift, but I guess other people must manage it. Ask your wife, as long as she would be happy to do it I'm sure it will work out.
You could just move there for now and keep your eye out for somewhere more suitable for you, and wait to start a family when you are somewhere you think you'll be happy.