The abductors took the baby and carried her away in a pram about 12:30 pm, just six hours after the mother gave birth about 6:30 am, a police spokesman said.
Police had launched a wide search for the women, even using a helicopter in their hunt.
One of the women was said to have gone into the new mother's hospital room pretending to be a nurse. On the pretence of taking a photo of the baby girl, she had left the room with the infant, daily Bild reported.
She was described as wearing jeans, aged about 30 and about 170 cm in height, police said. She appeared to be of foreign descent, the spokesman added. She wore a white top and a white headscarf.
The second woman, who was waiting outside the room with a pram, is described as being about 25, very overweight, approximately 1.65 metres tall and blonde-haired.
She wore light-coloured jeans, a light-coloured pullover and a dark brown jacket.
The infant wore a polka-dotted romper suit. The mother was being treated for shock in the women's ward of the hospital in Frankfurt's Höchst district.