Two people were removed from their vehicles by emergency services, police said.
The pregnant woman was airlifted to Whangarei Hospital in serious condition.
The man who was seriously injured was taken to hospital by ambulance.
Only one north-bound lane is open and the Serious Crash Unit are on the scene.
Debris is being cleared from the road. Tow-trucks are on their way to move the damaged vehicles.
A St John spokeswoman said seven other people were involved in the crash. They had minor injuries or no injuries and were treated by St John staff at the scene.