The Ontario Provincial Police say the crash happened at about 1:30 p.m. Tuesday, in the eastbound lanes of the highway, just east of Port Union Road in Toronto.
Police say the crash occurred after the driver of a Pontiac Sunfire lost control, hit a cement barrier and was then hit by the container truck.
The 37-year-old female driver of the Sunfire was taken to an Ajax hospital with minor injuries, along with the 15-year-old girl and month-old baby riding in the car.
The two minors were subsequently taken to the Hospital for Sick Children in Toronto "in critical condition," police said.
The 43-year-old man driving the container truck was not injured in the collision.
The eastbound lanes of the highway were closed until about 6 p.m. as police investigated the crash.