Researches don't know why, but a mother's traits appear to be linked to the chances her 3-year-old child will have an accident.

Noting that accidents are the leading cause of childhood death and disability, doctors at McGill University in Montreal studied 918 children in an attempt to find common factors among accident-prone toddlers.The researchers surveyed aspects of family and health of children born in 1983 in the Montreal community health district, then re-questioned parents periodically until the children were 4 years old.

The factors most strongly linked to the toddlers' accident rates were not factors such as the sex or health of the child, the researchers found, but facts about mothers were strongly linked.

"A child of a single, unemployed, smoking mother, who does not have a younger sibling, has a very high probability of sustaining an injury requiring treatment," the researchers said. A toddler with these four risk factors would have a 70 percent chance of sustaining injury by age 4, compared with a 20 percent chancefor a toddler with no risk factors.

Low family income and low educational level of mothers was not linked to higher accident rate.

Almost 60 percent of the accidents were falls, and 72 percent occurred in the home.

Writing in the American Journal of Diseases of Children, the researchers said none of the factors associated with higher accident rates "has a readily understandable link to injuries. This suggests they may be serving as 'markers' rather than being causative factors," the doctors said.