Thomas Hunter, 59, of Mansfield Road, Mansfield, had admitted causing the eight-vehicle crash on the A34 at Hinksey Hill, Oxford, on 25 August.
Isla Wiggin, of Fleet, Hampshire, died two days later. Her mother Collette's unborn son also died in the crash.
She told a court Hunter had "completely ruined" her family's lives.
Collette Wiggin also suffered a broken neck when Hunter drove his Volvo lorry into the back of a stationary queue of traffic at 43mph.
At Oxford Crown Court, prosecutor Michael Roques said another driver described the lorry "ploughing through all the other vehicles in the queue, scattering them like skittles".
Defence barrister Alexander Stein said his client could not remember the crash and had no idea why he had lost concentration for between eight and 10 seconds.
The crash forced the closure of the northbound carriageway of the road for almost 10 hours.
Mrs Wiggin read her own victim impact statement in court, asking for an example to be made of Hunter to send a message to other drivers.
She said: "My perfect life was ripped away from me, as the result of the thoughtless act of another.
"I am broken, all I ever wanted to be was a mother, and I absolutely loved being mummy.
"He has completely ruined the lives of good people who did nothing at all to deserve it."
She added: "A huge part of me died with my children."
Hunter admitted causing death by dangerous driving and serious injury by dangerous driving at a hearing last month.
Judge Ian Pringle told Hunter he had been "completely oblivious" to the queue of traffic, and had caused "catastrophic damage" to Mrs Wiggin's car.
Sgt Beth Walton of Thames Valley Police said the crash was "entirely preventable".
"If Hunter had taken care over his driving, and had been paying full attention to the road, Isla would be here today along with baby Harry.
"This case shows what the catastrophic consequences can be when drivers are not concentrating when at the wheel."
A lorry driver has been jailed for six years for causing the death of a three-year-old girl in a pile-up in which her pregnant mother suffered a miscarriage.