If this is going to be your first baby I will have to say that you will probably still have lots of time for your pup. I remember when my daughter was just a few months old I had bought a new puppy and with having a baby, they do sleep alot. I was never one to nap when my daughter did, she was a pretty good baby sleep wise at night. So I had lots of time to give to my dog.
Right now I have an almost 6 year old Step son who is here every other weekend, 3 and a half year old daughter, 3 dogs and 1 parrot. I have time for all of them and they all gets lots of attention. I would LOVE to have another baby but I do have some of those concerns as well, I think it comes natural as a mother to worry.