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."

Gayle, 25, scored 26 goals in 74 games for Palace after joining them from Peterborough for £6m in July 2013.
"Newcastle has a massive fan base and a great history so it is amazing to be here," he told the club website.
Scotland winger Ritchie, 26, featured 42 times last season as the Cherries maintained their top-flight place.
"It's an unbelievable feeling to come to a football club like this," said Ritchie.
"I loved it at Bournemouth - I had a fantastic time there and it had a huge impact on my career. But when a club like Newcastle comes calling, I couldn't pass up this opportunity."
Both fees are undisclosed, but Gayle's move - which happened on the day Newcastle's England winger Andros Townsend went in the opposite direction in a separate deal - is reported to be worth £10m, while Ritchie's signing is believed to have cost around £12m.
The attacking pair are manager Rafael Benitez's second and third signings since the club's relegation from the Premier League, following Wednesday's arrival of goalkeeper Matz Sels.
"Dwight is a great player, a proven goalscorer, and it is fantastic news that he has joined us," said the 56-year-old Spaniard.
"We have been following some wingers for a while and Matt was one of the best prospects for this team.
"He has great ability and pace, and as soon as we knew that Andros Townsend could be leaving, our priority was to finalise this deal."
Find all the latest football transfers on our dedicated page.

The 31-year-old Brazil forward, better known just by her first name, has signed a two-year contract with an option of a third.
She has recently been playing in Sweden for FC Rosengard.
Marta was part of the Brazil side which lost in the 2007 World Cup final to Germany in China.
Marta won five consecutive world player of the year titles from 2006-2010 and has finished in the top three of the voting in every year from 2004-2014.
Orlando City chief executive Alex Leitao said: "We are incredibly proud to bring Marta to Orlando, and I am personally very excited as I have been a fan of her for many years.
"Our technical team worked hard to add the best, most accomplished women's soccer player in the world to the roster."
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.
[NEXT_CONCEPT]
Newcastle United have signed Crystal Palace striker Dwight Gayle and Bournemouth winger Matt Ritchie, both on five-year deals.
[NEXT_CONCEPT]
Five-time world player of the year Marta Vieira da Silva has joined Orlando Pride in America's National Women's Soccer League.