A 22-year-old man and a 19-year-old woman have been held following the discovery at Packett Street, Fenton.
Staffordshire Police was called to the scene at 10:00 BST. A force spokesperson said post-mortem tests would take place on Wednesday.
Formal identification of the child has yet to take place.
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Scenes of crime officers have been examining the property and an alleyway behind it.
Det Insp Dan Ison said: "Our thoughts are with the little girl's family at this time.
"This is a very distressing incident and we are doing all we can to support those affected."
West Midlands Ambulance Service said crews found a child "who was sadly confirmed deceased".
A spokesman said: "They also treated a woman at the scene before she was transported to Royal Stoke University Hospital."

The baby, named Sion by officers, was recovered from the River Taff on 23 June. It is believed he died at birth.
The force said its main concern was to provide the mother with the emotional support she may need.
Police also want to find Sion's mother so he can be "laid to rest with his family name".
Det Insp Mark O'Shea said: "With the passing of time we hope that Sion's mother, or a family member, may feel more comfortable to come forward and enable us to support them and allow Sion to be laid to rest with his family name.
"We understand that Sion's mother has been through a traumatic time and I can reassure you that we have professionals in place with specialist skills who can provide you with support."
Suzanne Hardacre, head of midwifery at Cardiff and Vale University Health Board, said staff understood the mother might be frightened to come forward but urged her to get in touch.
"We are here to help you. We have a range of health care professionals available to give you any emotional support or medical attention you may need. Any care you receive from us will be in total confidence."
"Please contact us on this telephone number 02920 742679 anytime of the day or night, we want to make sure you are ok."

Passengers walked along the tracks for more than five minutes because a fault with the track led a train to get stuck outside Shepherd's Bush station.
It came to a halt at about 18:00 BST on Wednesday.
TfL said the evacuation was "safe and routine". Passengers thanked crews for "leading them into the light."
It said it was investigating why the line which carried the electrical current to the trains was dislodged.
All affected customers have been offered a full refund.
Jasmin Barras, one of the evacuated passengers, said TfL staff were "fantastic".
"It only took five minutes to walk once we could get off the train," she said.
"But I was in the very end carriage so first to get off - it would have been considerably longer for people further down the train."
Commenting on Twitter, Helen Pratt said: "Well, that was fun on the Central Line in the dark. Thanks TfL for sending friendly staff to lead us into the light."
A TfL spokesman confirmed nobody was hurt and said: "Emergency staff attended and led passengers off the train and back onto the platform."
Two people have been arrested on suspicion of murder after a two-year-old girl was found dead at an address in Stoke-on-Trent.
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