(AP) -- At least 13 child abuse cases in Iowa have led to death or critical injuries in 1999 and 2000. The children ranged in age from 3 months to 4 years. In about half the cases, prior abuse allegations had been investigated.

Dickinson County

SPIRIT LAKE -- Kyler Klaassen, 21 months, died in August 1999 from injuries sustained in March 1998. His father, Korey Klaassen, 31, was convicted of child endangerment and faces trial March 20 on a first-degree murder charge.

SPIRIT LAKE -- Shelby Duis, 2, died Jan. 4. Doctors said she previously suffered a broken hand and broken ribs. Her mother, Heidi Watkins, was acquitted of murder but convicted of child neglect. Her mother's live-in boyfriend, Jesse Wendelsdorf, was acquitted of murder and sexual abuse charges.

Hamilton County

ELLSWORTH -- Jack Michael Loder, 14 months, died Aug. 4 after falling at home. Hamilton County Attorney Pat Chambers said reports from the medical examiner would help determine whether criminal charges are filed.

Mahaska County

OSKALOOSA -- Frank Charbonneau Jr., 23 months, suffered injuries that police said were consistent with shaken-baby syndrome. His mother, Miranda Charbonneau, 21, pleaded guilty to child endangerment in exchange for testimony against her boyfriend, Clarence Yeo Jr., 23. He was charged with child endangerment.

Marshall County

MARSHALLTOWN -- Jarren Ozburn, 3 months, died July 30. He suffered broken bones and other injuries, and lived for two days after his parents, Adam Ozburn and Jill Streets, took him to a hospital. No one has been charged.

O'Brien County

SHELDON -- Daniel Chrestiansen, 2 months, died on May 24, a week after police said he was shaken and thrown at home. His father, Jeffrey Chrestiansen, 39, pleaded guilty to involuntary manslaughter and child endangerment.

Plymouth County

LE MARS -- Trevor Boldra, 6 weeks, died in February. His father, James Boldra, 22, pleaded guilty to attempted murder, child endangerment and voluntary manslaughter. He told a judge he shook the baby.

Polk County

DES MOINES -- Wyatt Green, 4, drowned at Gray's Lake in Des Moines in July. An investigation concluded lack of supervision on the part his parents, Karl and Susan Green, contributed to his death. The Greens are listed on Iowa's child abuse registry, but criminal charges were never filed.

DES MOINES -- Rodneisha Hodge, 17 months, died March 18 after a breathing tube came out of her neck and her 16-year-old mother was unable to reposition it. The baby breathed with the help of a ventilator, ate through a gastric tube and needed constant care. No charges have been filed in the baby's death.

DES MOINES -- Destany Miller, 3 months, died Oct. 20 of what police said was cranial and cerebral trauma consistent with shaken baby syndrome. Her father, Brian Miller, 19, was charged with first-degree murder.

DES MOINES -- Joel Vasquez, 21 months, died of severe head injuries. Police said he was slammed against the floor. Baby-sitter Tifany Myers, 19, pleaded guilty in October to second-degree murder.

ALTOONA -- Benjamin Vorwerk, 21 months, died from a head injury caused by blunt trauma on Nov. 17. Leann Werts, 30, who runs a state-registered child-care service in her home, was charged with first-degree murder.

Woodbury County

DENISON -- Kayla Adair, 4, died in February of an obstructed bowel. Authorities confirmed during an autopsy that she had been sexually assaulted. A family friend, Arthur Harold Bugely III, 21, was convicted and sentenced to 25 years in prison.