Study: Women Pregnant With Boys Eat More

By EMMA ROSS
AP Medical Writer

June 5, 2003, 7:29 PM EDT

LONDON -- Women pregnant with boys tend to eat about 10 percent more
calories a day than those carrying girls but don't gain more weight, new
research indicates.

The study, published this week in the British Medical Journal, appears
to explain -- at least in part -- why newborn boys are heavier than
girls and suggests that signals between the fetus and the mother drive
the appetite during pregnancy.

Boys are on the average 3.5 ounces heavier at birth than girls. The
study by researchers from the Harvard School of Public Health and the
Karolinska Institute in Stockholm, Sweden, is the first to examine
whether that difference could be due to the mother eating more.

The scientists assessed the diets of 244 American women one week before
they came to the hospital for a routine prenatal checkup at 27 weeks of
pregnancy. All the women later gave birth to normal-weight babies at
full term.

The researchers found that women who gave birth to boys were consuming
about 10 percent, or 200, more calories per day than those who went on
to bear girls.

Yet the amount of weight mothers gained during pregnancy did not differ
between those who had girls and those who had boys.

"This sounds undoubtedly driven by the fetus," said Kent Thornburg, a
fetal physiologist at Oregon Health Sciences University who was not
connected with the study.

Thornburg said the findings do not necessarily mean that boys are
heavier solely because their mothers eat more.

"That would lead to the conclusion that the more a pregnant woman eats
the bigger her baby will be and that female babies would be larger if
only their mothers ate more," he said. "A more realistic hypothesis is
that fetuses stimulate the appetite in their mothers in proportion to
their requirement for optimal growth."

Scientists do not understand exactly what causes appetite to increase
during pregnancy, but the study's findings suggest there is a chemical
communication between mother and fetus so that males can grow faster
than females, with the mother being signaled to eat more to enable that
growth, Thornburg said.

Thornburg said the findings could be relevant to the recently discovered
relationship between growth in the womb and the risk in adulthood of
illnesses such as heart disease and diabetes.

"A decade ago, we thought that the primary risk for chronic disease in
any apparently healthy baby was solely the result of genetic endowment
from parents," Thornburg said. "We now know that the access to nutrients
by the fetus is important in determining prenatal growth rate and thus
lifelong health."

The study's authors said their results indicate that male fetuses may be
more vulnerable than female ones to problems linked to fetal nutrition.

* ___

On the Net:

The British Medical Journal: http://www.bmj.com

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