Prosecutors have said Shanann Watts' family consented to the deal.
A court-appointed lawyer for Watts said: "Although he understands that words are hollow at this point, he is sincerely sorry for all of this".
Christopher Watts, 33, was spared the death penalty at the urging of family members of his wife, Shanann, 34, who was 15 weeks pregnant, and their daughters Celeste, 3, and Bella, 4.
'Prison is too good for you.
"Your life is between you and God and I pray that he has mercy for you".
Watts, 33, was formally sentenced to consecutive life sentences for the murders.
The girls' bodies were found submerged in an oil tank, on property owned by the company Watts worked for until his arrest.
As a prosecutor detailed the injuries found on the bodies, Rzucek leaned forward, gasping. Prosecutors have said the reports would be released after Watts was sentenced.
Rourke said that investigators never believed that Watts was being entirely truthful. Celeste had no visible injuries, he said.
At the end of July, Chris Watts told her that his divorce was official, Kessinger said in the report, which was published online last week. Through tears, she told her son: "I have known you since the day you were born into this world". "But we will remain faithful as your family ... we love you and we forgive you, son". He kept his head down for much of the hearing, speaking only once to confirm that he did not want to make a statement before Judge Marcelo Kopcow imposed his sentence.
In police interviews Watts said he had killed his wife after seeing her strangling one of their children on a baby monitor.
You can watch his reaction to the sentencing here.
It's not clear exactly why Watts killed his family.
An unsealed arrest warrant revealed Watts had been having an affair with a co-worker.
At today's hearing, the district attorney alleged that Shanann Watts had been trying to save the marriage for weeks - texting her husband and buying self-help books, even as he shopped for jewellery and holiday spots to take his "new love".
After they were discovered, Watts told police that it was Shanann who strangled the girls after he told her he was leaving her. Officers initially handled the search and soon sought support from Colorado investigators and the Federal Bureau of Investigation.
Christopher Watts spoke to local television reporters from the front porch of the family's home in Frederick, a small town on the plains north of Denver where drilling rigs and oil wells surround booming subdivisions.
He pleaded for their safe return, telling reporters the house felt empty without Bella and Celeste watching cartoons or running to greet him at the door.
"There isn't a day that goes by that I don't cry for my family".