Rachel Thorold, 36, was pushing her five-month-old son Louis in his pram along a pavement beside the A10 in Waterbeach on Friday January 22, Cambridgeshire Police said.
The force said that at around 3.50pm a grey Mazda 2 was in collision with a white Renault Master van, and the van hit Ms Thorold and her son’s pram.
Louis died and Ms Thorold, of Gibson Close, Waterbeach, was taken to Addenbrooke’s Hospital in Cambridge where she remains in a critical but stable condition, police said on Monday.
The driver of the van and the driver of the Mazda suffered slight injuries and remained at the scene.
Police are appealing for witnesses or anyone who may have dashcam footage of the collision or moments leading up to it.
Detective Sergeant Mark Dollard, from the road policing unit, said: “This is an extremely tragic and sad incident and our deepest condolences go out to the family of Louis, who are being supported by a specially-trained officer.
“A thorough investigation will now be conducted by my team and I am seeking help from the public.
“While it is too early to say how the collision happened, I want to remind all road users of their responsibilities to drive with care.”
Anyone with information should call 101 or visit www.cambs.police.uk/report quoting incident 278 of January 22.
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