A northern Iowa couple has been charged with murder in connection with the death of their 4-month-old son, whose body was found covered in maggots in a baby swing at the family's home.

Cheyanne Renae Harris, 20, and Zachary Paul Koehn, 28, were arrested Wednesday on charges of first-degree murder and child endangerment.

Their son, Sterling Daniel Koehn, was found dead Aug. 30 after Koehn called 911 requesting an ambulance to the couple's Alta Vista apartment, court records show.

When Chickasaw County sheriff's deputies and medics arrived, they found the deceased boy sitting in a powered swing in a bedroom separate from where Koehn, Harris and their older child slept, according to criminal complaints filed in court against the couple.

An autopsy of the baby's body revealed "maggots in various stages of development in his clothing and on his skin," court records show.

A forensic entomologist studied the maggots to determine that Sterling had not been removed from the baby swing for more than a week, and he had not had a diaper change or bath in that time, court records show.

The State Medical Examiner ruled the death a homicide, and the cause of death was failure to provide critical care.

"The facts of this case go far beyond neglect and show circumstances manifesting an extreme indifference to human life," Chickasaw County Sheriff's Deputy Reed Palo wrote in the criminal complaints.

When deputies first arrived to the couple's apartment, Koehn reportedly told them that his girlfriend, Harris, had fed Sterling that morning "and he was fine." Koehn said Harris checked on the baby a couple of hours later, and he had died, according to the complaints.

This story was not consistent with autopsy findings and other investigation, court records show.

Harris and Koehn were jailed in Chickasaw County. Their preliminary hearing was scheduled for Nov. 2.

Alta Vista is about 125 miles northeast of Des Moines.

The Associated Press contributed to this report.