An Auckland Hospital spokeswoman said the woman's injuries, initially thought to have been serious, were minor and she had been discharged from hospital today.
If her unborn child had been affected she would not have been discharged, the spokeswoman said.
Te Atatu Fire Station officer Geoff Gardner, who attended the crash, said there had been serious concern for her wellbeing.
"The lady was status two [serious condition] and pregnant so [the police] were fearful that the consequences could escalate.''
He said the woman's husband arrived at the scene shortly after emergency services and accompanied her to hospital.
Police said the serious crash unit and Waitemata CIB were investigating.
The incident was one of several serious crashes around the country this weekend.
Two people were taken to hospital after a car crashed into a shop on Cascades Rd in the Auckland suburb of Pakuranga about 2am today.
On Saturday, a man died after his motorbike and a ute collided in the Waikato town of Maramarua.
Police said the 31-year-old Auckland man died in hospital from injuries sustained in the crash, at the intersection of Kopuku Rd and Symes Rd.
Also on Saturday, one person was taken to hospital and another two treated for injuries after a crash on State Highway 1 near Kawakawa in Northland.
And an 18-year-old man died after the car he was in came of Pariwai Rd in Thames about 4.25am yesterday. Just hours before, police had taken the car keys from a drunk driver from the same car.
Another six people were injured in crashes on Friday, including a 25-year-old woman who suffered life-threatening injures when struck by a petrol tanker in Dunedin.
Carnage on the roads:
Sunday, 4am: A pregnant woman was injured in a crash on Auckland's northwestern motorway.
Sunday, 2am: A car crashed into a shop in Pakuranga, Auckland, injuring two.
Saturday, 3.50pm: A man died after his motorbike and a ute collided in Maramarua, Waikato.
Saturday, 9.45am: Three people were injured in a crash near Kawakawa.
Saturday, 4.25am: An 18-year-old man died in a crash in Thames.
Friday night: Four people were injured, one critically, in a head-on collision in Waikato.
Friday, 8.25am: A a 25-year-old student was hit by a petrol tanker in Dunedin.
Friday morning: An elderly woman was hit by a car while at an ATM machine in Waihi.