Newborn baby and mum missing in NSW

A young mother and her newborn baby are missing after the pair failed to return home from a short trip to buy cigarettes.

Police are appealing for help in locating Telitha Perry, who phoned her sister on Monday morning saying she was walking to a nearby service station in Metford, near Maitland, to buy cigarettes.

They say Ms Perry is developmentally delayed.

It's believed Ms Perry was with her three-week-old daughter Kamila-Lea, who was last seen wearing a white and pink jumpsuit and being pushed in a blue three-wheeled jogging stroller.

Later in the day Ms Perry contacted her sister to tell her she was in Mt Druitt, in Sydney's west.

But the mother and daughter haven't returned home.

She was last seen wearing a light green shirt, black singlet and leggings, and was carrying a brown bag.