Let me assure you that I adore all animals. I'm a firm believer in introducing your pet to your baby and your baby to your pet. But to be fair to your pet, many dogs and cats view small moving objects as playthings, and they respond instinctually to certain movements. Of course your pet would never want to hurt your baby. Animals who must survive in the wild instinctually stay still when they are in danger until their instinct tells them it's time to run.
Human babies are totally dependent on adults.
Their automatic response to any distress is to scream and move and carry on to attract attention. Such a response could result in an attack by your beloved pet. You owe it to your pet and baby to teach them how to respond to each other.