TUESDAY, Feb. 26 (HealthDay News) -- Children of women who are diagnosed with an alcohol disorder during pregnancy or within a year after giving birth have a three-fold higher risk of dying from SIDS -- sudden infant death syndrome -- compared to babies whose mothers do not have alcohol issues, according to a new Australian study.

In the study, a mother's problem drinking was implicated in about one out of every six SIDS deaths, according to the researchers. Alcohol abuse by the mothers was also linked with about 3 percent of the deaths caused by something other than SIDS, the researchers found.

"Maternal alcohol-use disorder is a significant risk factor for SIDS and infant mortality excluding SIDS," wrote researcher Colleen O'Leary, of Curtin University in Perth, and colleagues.

The study was published online Feb. 25 and in the March print issue of the journal Pediatrics

SIDS is defined as the sudden death of an infant less than 1 year old that can't be explained after thoroughly investigating, according to the U.S. Centers for Disease Control and Prevention.

Overall, SIDS deaths have dropped by more than half since 1990, the CDC noted. Even so, it is still the leading cause of death among U.S. babies aged 1 month to 1 year.

In 2009, about 2,200 U.S. children died from SIDS. The rate is still disproportionately high among some groups, including American Indians, Alaskan natives and blacks, the Australian researchers said.

Australia has a higher-than-average infant death rate, with more than four of every 1,000 live births affected, according to study background information.

Experts have known that certain risk factors increase the chances of SIDS, including bed sharing, maternal smoking and putting a baby to sleep on their stomach. Prevention guidelines recommend positioning babies on their backs.

More recently, researchers have focused on alcohol.

The new study findings did not surprise David P. Phillips, a professor of sociology at the University of California, San Diego, who also has reported a link between parental alcohol intake and SIDS deaths. As alcohol consumption rises -- such as on New Year's and weekends -- so do the number of SIDS deaths, he found.

"We know that when people are under the influence of alcohol, they perform tasks much more poorly, including parenting," he said.

For the new study, the Australian researchers evaluated nearly 78,000 live births from 1983 to 2005. They found nearly 22,000 of the mothers had an alcohol diagnosis such as acute alcohol intoxication or dependence. About 56,000 did not.

In all, more than 300 children died from SIDS and nearly 600 others died of other causes.

Although the study found an association between infant death and maternal drinking, it didn't establish a cause-and-effect relationship. The researchers can't explain exactly why alcohol abuse and SIDS are linked. They speculate that the alcohol has a bad effect on the development of the brainstem during pregnancy.

Alcohol disorders after pregnancy may lead to parental behavior that harms the child, Phillips said. A mother or father, for instance, might roll over onto a sleeping baby in the bed after drinking too much, he said.

Another expert said the new study could help make a difference.

"This study will probably shed light on a problem that is basically preventable," said Dr. Magaly Diaz-Barbosa, medical director of neonatology at Miami Children's Hospital, and a clinical assistant professor of pediatrics at Florida International University's Herbert Wertheim College of Medicine.

''If we can modify this risk factor, we could actually affect and decrease the number of SIDS victims," she said.

The percent of women with an alcohol problem in the Australian study was high, at about 28 percent, Diaz-Barbosa said. Fewer U.S. women may be affected, she said.

More information

To learn more about SIDS, visit the U.S. Centers for Disease Control and Prevention.