Caffeine may put fetuses at risk

WALNUT CREEK, Calif. – Consuming large amounts of caffeine during pregnancy by drinking coffee, soda, tea or hot chocolate increases the risk of miscarriage, a new study reveals.

Women who ingest 200 milligrams or more of caffeine per day are twice as likely to miscarry as women who consume no caffeine, the study by Kaiser Permanente found.

That equals about two cups of coffee daily or five 12-ounce cans of soda.

“We recommend avoiding caffeine, but if people are compelled to have it, we tell them for sure to limit it,” said Dr. David Walton, Kaiser’s regional chief of perinatology.

Previous studies have shown a link between caffeine and miscarriage. But critics questioned those findings, arguing that the results may have been skewed because many healthy pregnant women reduce their caffeine intake because of nausea and vomiting.

The Kaiser study addressed that issue by examining both women whose caffeine consumption changed during pregnancy and those whose had no change.

It also adjusted for such factors as a mother’s age, race, income level and whether she smoked, consumed alcohol, used a hot tub or had a previous miscarriage.

The study appears online today on the Web site of the American Journal of Obstetrics and Gynecology, www.ajog.org.

“Caffeine crosses the placenta barrier easily,” said Dr. De-Kun Li, the study’s lead investigator.

Once in the fetus, it may stay there longer because fetuses have an underdeveloped metabolic system, Li said.

In large quantities, caffeine may also decrease placental blood flow and harm cell development, experts say.

Not only should pregnant women limit their caffeine consumption, women who are attempting to become pregnant should consider doing so as well because the first 20 to 40 days after an egg is fertilized is a key time in its development, Walton said. As a result, harm could occur before a pregnancy is confirmed.

The researchers examined caffeine use among 1,063 pregnant Kaiser members in the San Francisco area from October 1996 to October 1998.

Interviewers asked the women about the frequency and amount of beverages they consumed and whether they changed their patterns after becoming pregnant.

The researchers then estimated the amount of caffeine consumed by assuming that for every 150 milliliters of a beverage, coffee contains 100 milligrams of caffeine, tea 39 milligrams, soda 15 milligrams and hot chocolate 2 milligrams.

Even decaffeinated coffee contains some caffeine. They estimated 2 milligrams.

The researchers then compared caffeine use with rates of miscarriage during the first 20 weeks.

“The increased risk of miscarriage appeared to be due to caffeine itself rather than other possible chemicals in coffee because caffeine intake from non-coffee sources showed the similarly increased risk of miscarriage,” the study found.

While there was some indication that consuming less than 200 milligrams of caffeine daily might increase the risk, the numbers were not large enough to be statistically significant, and thus no conclusions could be drawn about smaller amounts of caffeine, Li said.

Walton said he is concerned that women who have had a miscarriage will now blame themselves because they drank coffee during their pregnancy. He noted that many other factors can lead to miscarriages.

Kaiser urges pregnant women to drink no more than the equivalent of one or two cups of coffee per day, if they cannot avoid caffeine altogether.

“What we’re trying to tell people is that a lot of times we use caffeine because we have bad lifestyles,” Walton said. “So if we can make our lifestyles better and exercise more and sleep better, then caffeine isn’t such a compelling part of our life.

“We’re really trying to get across the message that healthy lifestyles can help us reduce our intake of things like caffeine.”

Experts suggest seeking a natural energy boost by taking a brisk walk, doing yoga stretches or snacking on dried fruits and nuts.