Blair Cashin didn't intend to deliver his wife's baby at home, but when her waters broke and a head popped out minutes later he became a makeshift midwife.

The panicked Wellington man dialled 111 and a Wellington Free Ambulance call taker talked him through the delivery in a bathtub.

Two contractions later, son Oliver was born. He gave the newborn to wife Sasha and then removed the placenta with the guidance of the call taker.

All the while an ambulance and the couple's midwife were still rushing to their Brooklyn home.

"I guess [I was] freaking out really," Mr Cashin said yesterday. "It was kind of a surreal moment. I felt like I was in a movie."

Mrs Cashin had had her first contraction about four hours earlier. They remained mild for about three hours.

At 7.30pm their midwife said everything sounded OK and told them to call back in an hour.

The couple were relaxed - Mrs Cashin was in labour with their first child, George, for 27 hours.

However, the mood in the house changed 50 minutes later when her waters broke as she was preparing to go to hospital.

Mr Cashin called for help about 8.30pm and the ambulance arrived about 15 minutes later.

Oliver was born about 8.40pm and spent three nights in hospital with Mrs Cashin. Five weeks on from his rapid entrance the pair are doing well.

Mr Cashin said the terrifying experience was made a lot easier by senior ambulance call taker Lorraine Harrower, who provided valuable guidance and calmed him down during the birth.

"She just kept me focused on making sure mum and baby were safe and healthy."

He had written to the ambulance service to say thanks.

"I'm sure it's a pretty thankless job most of the time."

Mrs Harrower said staff were trained to deal with an array of scenarios. She had helped deliver about 10 children over the phone since starting the job about three years ago.

"It was an exciting call and it had a really good result at the end of it."

- © Fairfax NZ News