Instead of a peaceful water birth she was delivered by ACT intensive care paramedics - and some help from dad - in the back of an ambulance on the way to hospital yesterday afternoon.

Celeste couldn't wait and was born at the side of the road just metres from Calvary Hospital.

Mother Tracey and baby - who was born at 4.25pm weighing 2.9kg - of Ngunnawal, were doing well last night, after an eventful day.

Celeste is a sibling for Izaac, 2, and father, Rod, admitted they now had a bit of a story to tell friends, relatives and one day Celeste.

''It was completely not what was planned,'' he said.

He said his wife had been due to give birth next week but had experienced what she thought were Braxton Hicks contractions in the afternoon.

She had gone to a friend's house as the contractions intensified and Mr Hemley, who had been at work, got a call at 3pm to come home.

An anxious cab ride later he arrived home, picked up the car and went to the friend's house.

It was soon clear Ms Hemley was having contractions and they called an ambulance.

She gave birth just as they were pulling into the Calvary driveway.

Mr Hemley said, ''The paramedics were great ... they were keeping us calm, letting us know what was happening, where we were at and how far away we were from the hospital.''

ACT Ambulance Service duty operations manager Robert Wiggins said while they had been in sight of the hospital, for the safety of the delivery they have to stop once the baby starts moving.

He said the intensive care paramedics involved in the delivery, Jean Pallet and Kylie Hood, were thrilled with the result.

''It's one of a paramedic's favourite jobs; it's a magical time to be able to share with new parents and a highlight of a paramedic's career,'' he said of delivering babies.

''They're very happy. One of the paramedics, it was her 29th birthday today and shortly after finishing her shift she was off to celebrate for two.''

Mr Wiggins himself has delivered five or six babies during his career.