When grandparents look out for children, their injury rates are about half of what is seen in organized day cares, according to a new study.

Researchers from the Johns Hopkins Bloomberg School of Public Health compared staying with a grandmother to outside day care and to staying with a mother.

Also, the odds of injury were significantly greater among children whose parents never married compared with children whose mothers stayed married throughout the child's life. Similarly, odds of injury were greater for children living without their fathers. These associations were independent of family income.

"Recent growth in the number of grandparents providing child care has some observers concerned they don't adhere to modern safety practices," said Dr. David Bishai, lead author of the study. "To the contrary, this research tells us not only is there no evidence to support this assumption, but families that choose grandparents to care for their children experience fewer child injuries."

A news release on the work did not give specifics on how many injuries occur overall, but did say that they are the No. 1 cause of death for children in the U.S. It also did not list what portion of children get which kind of care.

Bishai and colleagues analyzed data from the National Evaluation of the Healthy Steps for Young Children Program, which includes information on over 5,500 newborns who were followed for nearly three years.

The results are published in the November 2008 issue of Pediatrics.