ATLANTA — Nearly 1 in 50 of the most vulnerable U.S. residents — infants — have been abused and neglected, according to the first national child safety study in that age group.

In Utah, the rate among children younger than a year old — 1 in 100 — is half of the national rate reported in the study, according to state Division of Child and Family Services figures.

Researchers for the Centers for Disease Control and Prevention counted more than 91,000 infant victims of abuse and neglect from Oct. 1, 2005, to Sept. 30, 2006. In that same time period, 1,039 infants in Utah were abused, according to DCFS.

Most of the cases involved neglect, not physical abuse.

State statistics for abuse of children a week old or younger matched the national number, as nearly a third of the victims were newborn.

The chief contributing factor is domestic violence. However, maternal drug use was a contributing factor nationally and locally in the child neglect cases. About 18 percent of those cases in Utah were neglect due to alcohol use, including fetal alcohol syndrome and neglect due to methamphetamine abuse.

Maternal drug abuse is often discovered through blood tests while newborns are still in the hospital, CDC researchers and others said.

"That is the story here," said Dr. Howard Dubowitz, a professor of pediatrics at the University of Maryland School of Medicine.

The information came from a national database of cases verified by protective services agencies in 45 states, the District of Columbia and Puerto Rico.

Other studies have looked at national child abuse and neglect cases, but this is believed to be the first to focus on infants, said study co-author Rebecca Leeb, of the Centers for Disease Control and Prevention.

The results mirror what a study in Canada found, said Leeb, a CDC epidemiologist.

"We certainly were distressed" by the study's results, said Ileana Arias, director of the CDC's National Center for Injury Prevention and Control.

"It's a picture you don't want to imagine — that this number of infants is being mistreated," Arias added.

Only about 13 percent of the newborn cases were counted as physical abuse, meaning the large majority involved neglect.

Federal officials define neglect as a failure to meet a child's basic needs, including housing, clothing, feeding and access to medical care.

Things like abandonment and newborn drug addiction would qualify as neglect, not things like parents learning how to be parents," Leeb said.

Duane Betournay, DCFS executive director, said Utah may have half the national rate of abuse, but the severity of the incidents and time of abuse are about the same.