A Calgary man has been charged with assault after his four-year-old stepdaughter was taken to hospital with suspicious critical injuries last March, police say.

On March 11, 2018, city police were contacted by Alberta Children's Services regarding the child, who was taken to hospital by her mother in life-threatening condition, a release said.

Her condition was later upgraded to serious, but she suffered what are believed to be possibly life-altering injuries, police say.

At the time the girl was injured, her stepfather was the only adult in the home.

"It is alleged the stepfather's explanation of how the child received the injuries does not align with medical evidence," the release said.

After a nearly year-long investigation, the Calgary Police Service's child abuse unit has charged the man with aggravated assault.

Staff Sgt. John Guigon said that before the incident, the girl was a normal, healthy, happy child who was swimming, walking, running and talking.

"And now she's confined to a wheelchair, does not have full use of the left side of her body, has difficultly with cognition and speech," he said.

Police aren't identifying the 32-year-old accused because they say it would identify the victim. The man was released on bail. His first court date is Feb. 15.