Emergency services were called at 6.15am today following the collision between a van and a car.
A Cambridgeshire police spokeswoman said: “Officers are currently at the scene of a serious collision on the A605 between Coates and March.
“The collision, which happened at just after 6.15am today (3 June), involved a van and a car.
“Paramedics and fire crews also attended the scene and one woman has been seriously injured.
“The road has been closed and motorists are advised to avoid the area.