Too Much Caffeine Increases the Risk of Miscarriage
(CBS) Today’s New England Journal of Medicine has a study that links caffeine to the risk of miscarriage in pregnant women. Dr. Bernadine Healy tells us more about the findings.
For years, obstetricians and prenatal healthcare providers have suspected a connection
between caffeine and miscarriage, so they advised pregnant women to limit their caffeine intake. A new study in the New England Journal of Medicine reveals that five cups of coffee per day more than DOUBLES a pregnant woman’s chance of having a miscarriage.
In the meantime, the US Food and Drug Administration and the March of Dimes, which funds research on birth defects, have both advised pregnant women to curtail caffeine. Caffeine, which is easily passed to the fetus, stays in the body longer among pregnant women.
Unlike earlier research, the latest study looked at women in the first trimester, when most miscarriages occur. It also tried to account for a separate risk from genetic defects in fetuses and a possible risk from smoking.
The More You Drink, The Greater The Risk
The research team in Sweden and the United States found that the equivalent of one-to-three cups of American coffee increases the risk of miscarriage by 30%. Three to five cups raises the risk by 40%. Five cups or more yields more than doubled the risk.
Not All Coffee Are Created Equal
The findings are based on interviews with 562 women who had miscarriages between six to 12 weeks of pregnancy (the first trimester), and 953 pregnant women who did not. Since they were Swedish, they often drank stronger coffee than Americans did. The results are “translated” to American cups of coffee.
A cup of Swedish coffee typically carries about 180 milligrams (”mg”) of caffeine, compared to the 100 mg in a typical American cup of coffee.
Smokers May Not Have Increased Risk
Interestingly, among nonsmokers, more miscarriages occurred in women who drank at least 100mg per day. Among smokers, caffeine was NOT associated with increased risk of abortion. The researchers say this is probably because the smokers already face a higher risk of miscarriage.
Two Cups Still Okay
Dr. Sven Cnattingius of the Karolinska Institute in Stockholm directed the study. He suggests that pregnant women curtail their coffee to the equivalent of about two American cups per day.
Caffiene In Drinks & Medicine
Tea, cocoa and coke normally contain less caffeine per ounce than coffee. But the study suggests a similar effect on miscarriage for these drinks and for medications with caffeine, if enough is consumed. Caffeine is also present in chocolate.
On The Other Hand: The Morning Sickness Effect
The researchers also tried to account for the effects of morning sickness, which tended to exaggerate the impact of caffeine in earlier studies because nausea is more common in pregnant women with healty fetuses. Since morning sickness gives many women with healthy fetuses a distaste of coffee, more unhealthy fetuses are found among coffee drinkers.
Dr. Mark Klebanoff, at the National Institute of Child Health and Human Development, who was familiar with the findings, said it is still possible that morning sickness skews the results. “I think it will never be completely possible to rule it out, no matter how good a study you do,” he said. But Klebanoff said this study is probably the strongest yet, because it was specifically designed to answer whether caffeine promotes miscarriage. Other studies used data initially collected to resolve other questions.