The coffee or other caffeinated beverages a
woman drinks during her pregnancy might up the odds for a low birth weight
newborn or an extended pregnancy, a new study says.
The researchers included data on nearly
60,000 Norwegian women.
“As the risk for having a low birth weight
baby was associated with caffeine consumption, pregnant women might be
counseled to reduce their caffeine intake during pregnancy as much as
possible,” said lead researcher Dr. Verena Sengpiel, an
obstetrician/gynecologist at the Sahlgrenska Academy of Sahlgrenska University
in Goteborg, Sweden.
She believes the findings should also spur a
re-evaluation of current recommendations from the American College of
Obstetricians and Gynecologists, which advises that a pregnant woman’s caffeine
intake not exceed two cups of coffee per day.
However, because the study was observational
in nature, it can’t establish a cause-and-effect relationship between caffeine
and low birth weight, Sengpiel stressed. “We cannot say from our data whether
caffeine is the specific substance responsible for the fetus being at greater
risk of [becoming a] low birth weight infant, nor did we study if these babies
actually had special health problems during the neonatal period,” Sengpiel
said.
The report was published online Feb. 18 - 2013 in
the journal BMC Medicine.
In the study, Sengpiel’s team accounted for
all sources of caffeine, including coffee, tea, sodas and food including cocoa
(such as is found in desserts and chocolate), for almost 60,000 pregnancies
tracked by the Norwegian Institute of Public Health.
They found that while caffeine was not
linked to premature birth, caffeine from all sources was tied to a higher risk
for reduced birth weight.
For example, if an infant’s weight is
expected to be 7 pounds 15 ounces, every 100 milligrams of caffeine consumed by
its mother a day reduced a newborn’s weight by almost an ounce, the researchers
reported.
According to the Mayo Clinic, the average
cup of American-style brewed coffee contains between 95 and 200 milligrams (mg)
of caffeine.
Moreover, every 100 mg of caffeine consumed
per day increased the length of pregnancy by five hours. And when the caffeine
came from coffee (as opposed to other sources) the length of pregnancy was
extended eight extra hours, the study authors found.
Given this finding, it is likely that it is
not only the caffeine, but something else in coffee that is acting to extend
pregnancy, the researchers added.
Dr. Jennifer Wu, an
obstetrician/gynecologist at Lenox Hill Hospital in New York City, said, “Other
studies have indicated that caffeine can affect fetal weight, so this is in
accord with findings of other studies.”
Why caffeine might cause this effect is
unclear, she said.
“We do know that caffeine crosses the
placenta and the baby is not able to metabolize it very well, [so] it may
affect some of the factors associated with growth,” Wu theorized.
She advised that women limit the amount of
caffeine they consume during pregnancy. The World Health Organization says 300
mg a day, but in the United States the recommended amount is 200 mg a day, she
added.
Wu noted that is the amount of caffeine in
two small cups of coffee, not a “Starbucks size coffee.” There is less caffeine
in a cup of tea, or a piece of chocolate, which has about 35 mg of caffeine,
she said.
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