A Melbourne model has given birth to a baby in a bathroom - and she didn't even know she was pregnant.

Two weeks ago, 23-year-old Erin gave birth to a very healthy baby, named Isla, weighing 3.5kg.

Watch the video above

But the unusual pregnancy left Erin with no baby bump, no morning sickness, no cravings and all happened while she was using contraceptive injections.

"I wasn't showing obviously because I fit into everything. It's just really bizarre," Erin told 7NEWS in an exclusive interview.

Erin, pictured with her partner Dan, gave birth to a baby girl, despite not even realising she was pregnant. Credit: 7NEWS

Erin said she felt unwell on the day Isla was born, but didn't realise why until the baby's dramatic arrival, which she said was all over in about 10 minutes.

Her partner Dan said: "I heard a scream and I ran in there and then I saw the little one and I thought, hang on there's two."

The shocked new father quickly realised baby Isla wasn't breathing and rang triple-0.

Emergency advice

Audio from the phone call to emergency services revealed how the operator helped save the little girl's life.

"How many weeks pregnant was she? We didn't know she was pregnant," Dan can be heard telling the operator.

With help from emergency services, the new father was able to save the baby, who is now perfectly healthy.

Chevron Right Icon 'I heard a scream and I ran in there and then I saw the little one and I thought, hang on there's two.'

A surprise baby is often called a cryptic or stealth pregnancy.

One in 500 women don't know they are carrying a baby until they are 20 weeks into their pregnancy and one in 2500 don't find out until they are in labour.

"I'm still in shock, but you just adjust and this is our life now. We wouldn't change it," Erin said.