Never happened to me but my grandmother (who lives in a very nice neighborhood) was walking her two Pekingese and a large dog, who was unleashed, growled and then tried to jump on them. She instinctively dropped to the ground and hovered over them and she was the one who got bit and scratched. But who knows if the doggies would have made it through the attack without her.
It is very scary...keep your baby close!!
