Reputable and responsible breeders of dogs will NOT sell you a dog during the holidays.
PLEASE READ ALL THESE LINKS CAREFULLY and re-consider your timing for bringing a puppy into your home....
http://www.petrescue.com/library/no-pups.htm
http://www.veterinarypartner.com/Content.plx?P=A&C=29...
http://www.cyberpet.com/dogs/articles/lexi/cmgifts.htm
http://www.slate.com/id/2132035/
As for getting a dog while pregnant and also caring for another young child....it CAN be done....BUT, to give a dog any kind of proper care and attention at this time will take a lot of work. If you are up for that, so be it. more reading for you....
http://www.babylune.com/a-note-about-puppies-for-pregnant...
http://kennelkraze.com/2007/04/28/getting-a-puppy-with-a-...
I am NOT anti-dog.....I just KNOW personally from having had dogs all my life and also being a Mom with a toddler and 3 dogs.....it is NOT easy. When bringing ANY new pet into a home with young children or expecting a baby you must think very carefully before you jump at this.
Dogs are not born trained and calm.
As for breed?? This is a pretty personal choice. MOST breeds can be good with children if raised with them properly. Rescues CAN be good....but because you never truly know their background and history it can be tough to know for sure if a rescue will fit in with human babies.
Any, I hope you think long and hard about adding a puppy to the family. It CAN be a wonderfully rewarding experience but taking in a pet is NOT something to be taken lightly.
Oh, you might be interested in reading an article I recently wrote for an on-line magazine. There is a link within the article which has lots of useful information about kids and dogs.
http://www.thegreatdanegallery.com/obed_agil_etc.html
Good luck with whatever you decide to do. Be careful of the source from which you purchase a puppy. There are a LOT of non-respectable dog breeders in PA. Back-yard breeders doing it for the buck (generally don't have a clue about proper dog breeding), puppy millers and commercial dog breeders...also making money off their dogs...and pet shops (who buy thier dogs from the puppy millers and commercial breeders). Anyone advertising 'Puppies Ready for Christmas' or posting signs on the side of the road with 'Puppies for Sale' is generally someone to stay away from. Shelters and rescues CAN be a great place to find a pet.....but not at Christmas.....and the dogs gotten from a shelter or rescue must be carefully screened to be good with babies and children.
I hope this post helped :)