Firstly congratulations!!
I can say that you are going to be very busy!!!
I can highly recommend this blog site for tips on managing babies and dogs -
http://www.dogsandbabieslearning.com/blog/page/4/ - the series of articles on "magnetising" are very interesting and really helped us develop a safe approach to dog/baby interactions.
We haven't followed the advice in its entirety, as we do encourage the children to give the dog treats (under supervision), but the cues to give doggie space etc are spot on.
Honey was 3 when our first was born, and 4.5 when our youngest was born. Youngest has just turned 1 now.
We made sure that Honey had a reliable sit and wait (so she didn't try and race me up the stairs while I was carrying baby), and also waited for permission before jumping up to the sofa, in case I was sat there with a baby. She also has a bed in the lounge and a crate in the dining room which are completely off limits to children. Honey isn't a confident dog, and has struggled at times with the children - we have always made sure to respect her communication (growls) and teach her (and the children) ways of avoiding the situations she finds tough (move away etc). Also a reliable "give" in case she picked up baby toys/clothes/nappies...
In the early months, we used room dividers and playpens to ensure I could leave the room briefly without leaving dog and baby unsupervised together... but over time the playpen became more useful as a toy store (to stop Honey stealing teddies). It has now gone altogether, as with one toddler and one about to start walking, space is more important in avoiding confrontation. It can be a juggling act to keep watch on all, but we manage!
Your pup is likely to still need a very high level of attention at the time your baby is due - she will be in her teenage months and could well be in the secondary fear and teething stage, so do make sure you work out how you will be able to keep up her training/socialisation. Whether she will know to be more cautious around baby really depends on the individual dog. We tended to keep a pram in the lounge to use as a mobile moses basket so I could put baby down briefly, but safely out of the way of Honey. I also use slings (a stretchy wrap in the early weeks) so I could get on with jobs/dog walks/training while keeping baby close and safe. Do get Bella used to any equipment you intend to use - Honey found the pram terrifying... wasn't an issue as we didn't use it out of the house, and it was only scary for her if it was moving, but do get Bella used to anything along those lines that you think you might move!
You could find that Bella finds adapting to a new baby fairly tiring, so do watch that she doesn't get over-stimulated - we actually found Honey coped better when I eased off on other training and just let her adapt, with just occassional reinforcement of her basic training.
