A woman in Boulder, Colorado, who attacked and cut an unborn baby from an expectant mother last March has been found guilty of attempted murder by a jury.

Dynel Lane, 35, was found guilty of attempted first-degree murder, unlawful termination of a pregnancy and felony assault in the March 18, 2015 attack of Michelle Wilkins, who was seven months' pregnant, inside the assailant's home in Longmont.

Wilkins survived the attack but her baby, who was named Aurora, did not.

District Court Chief Judge Maria Berkenkotter has set the sentencing of Lane on April 29. She faces a minimum sentence of 16 years in prison, CNN reported.

The case began when Wilkins answered a Craiglist ad for baby clothes and went to Lane's home. Using two kitchen knives, Lane attacked her by beating and stabbing her. She cut into her uterus and removed the foetus.

Despite bleeding, Wilkins, who was 26 at the time, locked herself in a room and called 911.

Police officer Billy Sawyer and his partner, who responded to the call, said they found Wilkins "covered in blood."

Lane worked as a nurse aide in 2010 until her licence expired in 2012. The surgeon who attended Wilkins said the incision in the victim's abdomen "appeared to be well performed."

The doctor said "the person who did the incision would have to have researched the subject of caesarean births in books or online to achieve the level of accuracy."

During the trial, Lane's former boyfriend, David Ridley, testified that she told him she was pregnant and fooled friends and family into believing she was.

"She would say she had doctor appointments and we would take off work and sit in waiting rooms for hours, and something would always go wrong and she'd get agitated and we'd wind up leaving," he said, according to KDVR.

Ridley said on the day of the attack, he returned home to take Lane to a prenatal appointment only to find her covered in blood.

"She told David she just miscarried and the baby was in the bathtub upstairs," according to the police report.

Ridley found the baby in the bathtub and took her to the hospital. Lane refused to allow doctors to examine her and a police investigator "saw no visual signs of vaginal bleeding coming from Dynel or any signs of having recently given birth."

"Dynel admitted to Detective Stacey Graham that she cut abdomen open to remove [the victim's] baby," the police report said.

Prosecutors did not pursue murder charges as Colorado state law does not recognise a foetus as a person.

After the verdict was read, Wilkins said "it felt much bigger than myself, it felt like a triumph of justice for Aurora."

"For the time being, I am going to take care of myself and surround myself with family and friends," she said.