AURORA, CO (KDVR/CNN) – After two babies died while co-sleeping two years apart, their parents were charged with child abuse due to the similar circumstances of the cases.

Police began investigating Tierra Collins, 28, and Gregory Tyler Newton, 27, after their second baby, 3-month-old Nazairean Newton, died in June. The couple’s 7-month-old, Azian Newton, died two years prior in July 2014.

Police reports revealed both babies “died while sleeping in bed with the parents” and stated that at the time of each baby’s death, both parents “appear(ed) to be intoxicated or under the influence.”

Newton told police sleeping with Nazairean and the baby’s mother was a habit. However, after the baby’s birth, the parents had been warned not to co-sleep with him, according to an arrest affidavit.

“Tierra disregarded the advice given to her by Nurse Julia because Tierra said she was comfortable co-sleeping with Nazairean. Tierra said she is a light sleeper, however, in Tyler’s interview he said Tierra was a ‘heavy sleeper,’” the affidavit read in part.

In a December interview, Collins said she didn’t do anything wrong.

“I did not do anything that I felt to harm my babies. I was being a mother. I was taking care of them,” she said.

Newton agreed and said he didn’t blame himself for either baby’s death.

“It’s an unfortunate act. You know we… we’re young, but no, I never blamed myself,” he said.

The autopsy reports for each baby listed the cause of death as undetermined, but Arapahoe County coroner Dr. Kelly Lear-Kaul said that’s because suffocation leaves no trace.

“Asphyxial deaths don’t leave any marks in most cases, so there’s nothing for me to see at autopsy,” Lear-Kaul said.

The coroner says she believes the most likely cause of death for the babies is suffocation, but she can’t prove it.

The district attorney’s office charged the parents with two counts of misdemeanor child abuse, one for each baby.

If convicted, Collins and Newton could face three to 12 months in jail for each count.

Copyright 2017 KDVR, Family photos via CNN. All rights reserved.