The force said it launched a high-risk missing person investigation and has begun conducting urgent inquiries.
They have visited the family’s home in Southwark several times in the last 24 hours, but have found no trace of the couple or the baby.
Police believe it is likely that they are staying with friends or family.
Detective Chief Inspector Lucy O'Connor, who is leading the investigation, said: "We are becoming increasingly concerned for the safety of Baby Graham. Her parents have not followed the medical advice they were given and in doing so, could be putting her health at risk.
"There will be a time and a place to explore their reasons, but right now our priority has to be the safety of this very young baby."
She added: "While we would of course ask the public to keep an eye out for Baby Graham's parents, we believe it's likely they are being accommodated by relatives or associates.
"I would urge those people to put the welfare of this tiny baby girl above any other loyalty they may have and get in touch with the police.
"I would also appeal directly to Azara and Machel to do the right thing and to go to the nearest A&E so that Baby Graham can get the care she needs."
Police are urging anyone who sees the baby or her parents to call police on 999 quoting reference 21MIS011809, while anyone with any other information that could be useful are asked to call 101.
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