The car involved drove off from the scene
The crash happened just before 3.45pm this afternoon near to Beehive Lane.
A spokesperson for the Metropolitan Police said the woman has been taken to hospital.
It is not yet known how serious her injuries are.
The driver of the vehicle involved failed to stop.
The A12 is closed London-bound between the Gants Hill roundabout and Beehive Lane.
Tags: Redbridge, Ilford, Gants Hill, A12