A young woman with rapid-onset Alzheimer's disease has given birth to a healthy baby girl — but has no idea she has become a mother.

Rebecca Doig from Sydney, Australia was diagnosed with the degenerative brain disease last August.

Doctors discovered the 31-year-old was pregnant during a series of scans to see what was causing her memory loss.

Her condition has deteriorated so quickly, she can no longer recognize her daughter Emily, who was delivered by Caesarean section last week.

Emily's father Scott now has to look after his wife and newborn daughter.

"Emily is perfect," Doig told Australia's Sunday Telegraph. "She's a very beautiful little thing and very healthy. The road ahead is going to be extremely difficult — there's no two ways about it.

Doig is believed to be one of the first women to give birth at such a late stage of the disease.

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