Paraparaumu fire station officer John Arthur said the mother asked after her husband and child as she slipped in and out of consciousness.
"It's always difficult when there's children and families involved. All you can tell her is that the baby is with the ambulance staff. That's all you can say."
It took the fire crew about 30 minutes to cut the mother from the car, Mr Arthur said. She was taken by ambulance while her baby was flown by helicopter to Wellington Hospital where she later died.
"It was a single vehicle crash," Mr Arthur said. "It went off the road to the left and they've gone into the flax. They came back on to the road and they started rolling. It rolled five or six times."
When the first fire crew arrived at the scene about five minutes after the crash, the baby was out of the vehicle. It was not known if she had been thrown from the van during the crash or if a passersby had removed her.
An off-duty paramedic who had been travelling behind the car worked on the baby until ambulance crews arrived.
The mother, in her early 30s, was last night in a serious condition in intensive care, a Wellington Hospital spokesman said. The father had been released from hospital.
In a similar one-car crash near Taumarunui in the central North Island yesterday, a 4-year-old girl died when the car her mother was driving left the road and flipped.
Sergeant Paul Dowie said the mother and father, believed to be in their early 40s, were conscious as they were treated at the scene.
"They have crossed the centre line, hit a ditch on the other side of the road and the vehicle has rolled. Alcohol and speed were not factors," he said.
"The parents were in a coherent condition, so they were aware of what had happened."
Both parents were taken to Taumarunui Hospital. The father was in a serious condition.
The holiday road toll climbed to four with another fatal crash in Southland yesterday afternoon.
One person died and two others were injured in the head-on crash about 3.30pm between Te Anau and Mossburn.
"There were two cars. One was on the wrong side of the road, going up a hill," a police spokesman said.
Car passenger Sandy Paul Waenga Brown, 21, from Paua, was the first person killed in the holiday period, in a crash near Cape Reinga about 2.30am on Christmas Day.
Six people died in the last Christmas and New Year holiday period which runs from 4pm on Christmas Eve to 6am on January 3.
