Over night on it's own is terrible, for SOOOO many reasons (Fire being the most scary imo)
Outside on the street ...ummm depends if you can see the pram, if you know your neighbours etc ( I wouldn't but I have in the car when a sleep, but so I can see them)
but overnight is neglect, and dangerous and what about burglars/fire/illness/nightmares/
In mu job if we come across children on their own in a house, we ring the police and wait till they come, and also social services.
Selfish cow.