Study author Dr. Wen-Jui Han explained that it's likely not the work itself that may affect kids, but other factors that arise when women work non-traditional shifts.

For instance, research shows that young children whose mothers work nights and rotating shifts are more likely to be looked after by fathers and relatives and less likely to attend day care, which can help their growing brain, the researcher noted.

"This does not suggest that father care or relative care is not good," said Han, who is based at Columbia University in New York. "It rather suggests that these children whose mothers work nonstandard hours may miss out on an opportunity."

Han stressed that parents who work nights, evenings or rotating shifts should not blame themselves for how their children develop.

Mothers who work non-traditional shifts "are doing the best they can, so it is time for the nation to take a serious look at our family and childcare policies -- we need policies to support these families to do their best," Han noted.

An increasing number of men and women are working nights, evenings and rotating shifts, Han and colleagues report in the journal Child Development. For instance, a 1999 study showed that 27 percent of men and 33 percent of women who work full-time have non-standard shifts, an increase from the 1980s.

Previous research has shown these schedules can be hard on adults' physical and psychological well being, increasing the risk of depression, fatigue and marital instability. However, researchers have done little to examine how the schedules -- and their effect on adults -- influence young children.

To investigate, the researchers followed approximately 900 children through age 3, conducting a series of home visits and phone interviews. All of the mothers had worked during the child's first three years of life.

Night shifts included working hours from 11 PM to 7 AM, while evening shifts lasted from 3 PM to 12 AM.

The authors found that approximately one half of mothers worked a non-standard shift during their children's first years of life.

Children whose mothers worked non-standard shifts were more likely to be behind their peers in terms of mental development at age 2 and language ability at age 3.

Hopefully, this study will "open the dialogue" about the relationship between mothers' work and children's development, Han said.

"When parents are doing the best they can, and children may still suffer from the best, it only suggests that it does take a nation to raise a child," Han added.

SOURCE: Child Development, January/February 2005