WebMD Medical News
Louise Chang, MD
Jan. 22, 2008 -- Drinking more than a few cups of coffee or other
caffeinated beverages a day may
increase a pregnant woman's miscarriage risk, new research
Women in the study who consumed more than 200 mg of caffeine a day -- the
amount found in about two 8-ounce cups of regular-strength coffee -- had twice
the risk of miscarriage as pregnant women who consumed no caffeine.
Researchers say the study offers some of the strongest evidence to date
linking caffeine and miscarriage. But an expert who spoke to WebMD disagrees,
saying the jury is still very much out on the issue.
"The evidence just isn't there to say that caffeine is a risk factor for
miscarriage," says epidemiologist Lisa B. Signorello, ScD, who has studied
caffeine and miscarriage. "This is a very difficult thing to investigate,
and there is simply no gold-standard study that answers the question."
The new study included 1,063 women followed from early in their pregnancies
until up to 20 weeks of gestation by researchers from the Kaiser Permanente
Division of Research.
The women were interviewed at study entry about their caffeine consumption
and other factors known to be risk factors for miscarriage.
A total of 631 women (79%) reported reducing their caffeine consumption
after becoming pregnant, while 152 (19%) said they did not change their
Overall, 172 women (16%) in the study ended up having miscarriages.
According to the March of Dimes, about 15% of diagnosed pregnancies end in
The researchers concluded that consuming more than 200 mg of caffeine a day
doubled the risk of miscarriage, compared with consuming no caffeine at
Researchers cited their attempt to control for the confounding effect of
caffeine aversion during pregnancy as a major strength of
Early-pregnancy nausea and vomiting has been
linked to lower miscarriage risk, according to the researchers. Nausea and
vomiting may also contribute to caffeine aversion.
So women who are more likely to have a miscarriage might also be more likely
to continue drinking coffee, and this could explain the link between caffeine
and miscarriage seen in earlier studies.
But Signorello says there were not enough women in the study who did not
change their caffeine consumption to conclude that caffeine was a risk factor
in the miscarriage.
And the women who consumed the most caffeine were also more likely to have
other risk factors for miscarriage, including being over 35 years old, having a
history of miscarriage, having no morning sickness symptoms, and
smoking and drinking
Signorello is a researcher and epidemiologist with the Vanderbilt-Ingram
Cancer Center and the International Epidemiology Institute in Rockville,
"These women were very different from people who didn't consume
caffeine, and they were different in all the ways that are associated with
miscarriage," she tells WebMD.
Kaiser Permanente Director of Women's Health Tracy Flanagan, MD, tells WebMD
that she does discuss limiting caffeine with her pregnant patients.
She says that other than not smoking and avoiding drugs and alcohol, there
are few lifestyle interventions that have been shown to affect miscarriage
"The fact is, the vast majority of pregnancies that miscarry do so
because of chromosomal abnormalities," she says. "From a clinician's
standpoint, it is nice to be able to tell a patient that limiting caffeine just
may positively impact their pregnancy."
It is a message that financial planner Tammy Plotkin-Oren took to heart
after her first pregnancy ended in a miscarriage.
"I was a big coffee drinker, but I went totally cold turkey when I got
pregnant again," she says.
Now the mother of three young girls, Plotkin-Oren says she has no idea if
drinking coffee contributed to her miscarriage.
"For me, giving up caffeine was a no-brainer," she says. "I knew
it was something I needed to stop during pregnancy. Whether or not it made a
difference, I don't know."
SOURCES:Weng, X., American Journal of Obstetrics and Gynecology, online
edition.Tracy Flanagan, MD, director of Women's Health for Northern California,
Kaiser Permanente, Richmond, Calif.Lisa B. Signorello, ScD, International Epidemiology Institute, Rockville,
Md; Vanderbilt-Ingram Cancer Center, Nashville, Tenn.Tammy Plotkin-Oren, San Francisco.March of Dimes: "Miscarriage."
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