An Australian woman who suffers from advanced Alzheimer's disease has given birth, a first world experience.

On Tuesday, Rebecca Doig, 31 gave birth to Emily, but the she was indifferent to her new-born daughter, could not remember giving birth and had not been able to hold her baby.

Ms Doig, from Sydney found out she was expecting while having scans to assess her memory loss.

Her husband, Scott who has watched his wife's deteriorating health for the past nine months, described their new-born daughter, Emily as a miracle.

Emily is perfect. She's a very beautiful little thing and very healthy, he said.

Ms Doig was diagnosed with a rare form of the degenerative disease last August. She is believed to the first female patient afflicted with it.

Even so, she had a complication-free pregnancy and Emily Rebecca Doig was born healthy at 2.82kg by caesarean section at Hornsby Hospital.

The road ahead is going to be extremely difficult. There's no two ways about it, said Mr Doig.

We take every day as it comes because there's not a lot we can do about it.

I have a wife and a now a girl to look after.

Mr Doig has been learning how to feed and care for his daughter. To his wife who can no longer take care for herself, motherhood is an alien concept.

Before being diagnosed with Alzheimer's, Ms Doig was an independent, outgoing and bright young woman.

It's hard to see your wife lose that, said Mr Doig.

But she's my life and I'm not giving up on her.

Donations can be made to the Rebecca Doig Trust Fund at