By TAMAR LEWIN
Adding fuel to the debate
over mothers who work, a new analysis of the largest government child-care
study has found that early maternal employment has negative effects on
children's intellectual development.
"What we found was
that when mothers worked more than 30 hours by the time their children were 9
months old, those children, on average, did not do as well on school-readiness
tests when they were 3 years old," said Jeanne Brooks-Gunn of Columbia's
Teachers College, the lead author of the study. "In other work we've done,
we've seen that those negative effects of early full-time maternal employment
persist among children who are 7 or 8."
Where the mother did not
start working until the child was a year old, Dr. Brooks-Gunn said, there were
no significant effects.
The new study, to be
released today in Child Development magazine, is based on data from the
National Institute of Child Health and Human Development Study of Early Child
Care, which followed more than 1,000 children in 10 cities over three years,
examining maternal sensitivity, home environment, hours in child care and
quality of child care. The study by the institute, a branch of the National
Institutes of Health, is considered the most comprehensive child-care study to
date.
The analysis found that
3-year-olds from an average home environment, in average-quality child care,
whose mother did not work by the ninth month, scored at the 50th percentile on
the Bracken School Readiness test, which assesses children's knowledge of
colors, letters, numbers, shapes and comparisons.
Children in similar
settings whose mothers were employed by the ninth month scored at the 44th
percentile.
"That's a significant
difference," said another author of the study, Jane Waldfogel of
Columbia's School of Social Work. "I think moms and dads have to balance a
lot of different considerations, but if it is at all possible for mom to stay
home longer, or go back to work part time in the first year, that may be a good
thing."
The report is the latest to
use data from the national institute's study of early childhood development.
Last year, a report based on the data concluded that children who spent long
hours in day care tended to be more aggressive and have more behavioral problems.
Other reports based on the data have found no link between long hours in child
care and lower scores on school-readiness tests.
"For the last 20 to 30
years, as more and more mothers have been in jobs away from home, we've been on
a detective search for what it all means for the children," said Ellen
Galinsky, president of the Families and Work Institute, a nonprofit research
group based in New York. "It's very confusing to people on the sidelines,
because first one study says this and then another study says that. All of them
give us clues, but none of them give us answers. There are so many factors,
like the involvement of the dad, the quality of the child care, how much the
mother wants to be doing the work she is doing, how stressful the job is."
The new analysis examined
the number of hours the mother was employed rather than the number of hours the
child was in care — and found that maternal employment of 30 hours a week or
more by the time a baby was 9 months old was associated with lower scores on
school readiness tests at age 3.
"We really looked at
different questions," Ms. Waldfogel said. "They looked at early child
care, while we looked at early maternal employment. You'd think that those
would be the same, but it turns out that a third of the nonworking mothers put
their children in child care before 9 months."
The study analyzed how
other factors interacted with maternal employment in shaping children's
development. Children whose mothers worked by the time the babies were 9 months
old, and had insensitive mothers and poor-quality child care, had scores in the
37th percentile. The 3-year-olds who did best on the test, scoring at the 56th
percentile, were those who had sensitive mothers who were not employed by the
ninth month, and good-quality child care.
As other studies have
found, boys were more vulnerable than girls to the effects of early maternal
employment.
The new analysis included
900 white non-Hispanic children who were followed from birth to 36 months in
the national institute's study. The data on the 174 black and Hispanic children
in the study were excluded, both because the sample size was too small to
analyze separately and because a homogenous population made it easier to
separate out the effects of employment, Dr. Brooks-Gunn said.
In the families studied, 55
percent of the mothers were working by the third month, 71 percent by the sixth
month and 75 percent by the ninth month.