Congratulations!
As I mentioned in my introduction, I have two RR's (8 and 4) and a 16 month old little boy. My dogs have done great with the new addition. I think the key for us was continuing to include them in everything. We have pictures on the first day home from the hospital of me nursing Sam in our bed with a dog cuddled up on each side with a head on my leg. The dogs also each have a bed in Sam's room and are always welcome in there (although we do try to keep them from wrestling in his room!). Whenever I did anything with Sam when he was a newborn, I always invited the dogs along. Jumangi was very gentle with him from the start, Whiskey was very curious and had to be reminded that the baby was little and he had to be careful, but he caught on quickly.
We also set up all of the baby stuff - swing, bassinet, pack-n-play, nursery, etc - prior to the baby coming home so that the dogs were used to it.
The dogs had a bit of an adjustment with not getting 100% of the attention anymore, but they adjusted well. For the first month of so poor Whiskey would empty out his toy box onto any visitors hoping they were there to visit him instead of the baby!!

(Oh, and I also tried to make sure any visitors said hi to the dogs before paying all the attention to the baby.)
When Sam started getting moblie, Jumangi was a little unsure of him, but she is doing pretty well now, although she will not let him crawl all over her like Whiskey does. Whiskey thinks Sam is great now and they are great buddies. Both dogs will stay in Sam's room with him until he falls asleep.
I will post some pics of Whiskey & Sam (as soon as I figure out how!), they are adorable together!
Oh, and as far as them noticing me being pregnant, they didn't act much different. Although Whiskey was a little put out when my belly started to interfere with him sitting in my lap!

Anyway, hope this helps a little to at least reassure you. I am sure your dogs will love the new addition!
Tracy