A new study suggests that pregnant women who consume the amount of caffeine in one and a half to three cups of coffee a day may nearly double their risk of miscarriage.
The researchers also linked high caffeine consumption -- the equivalent of more than three cups of coffee a day -- in the month before pregnancy with a similar risk of miscarriage, said Dr. Claire Infante-Rivard of McGill University in Montreal, the main author of the report. It is being published today in The Journal of the American Medical Association.
The study also found that drinking the amount of caffeine in more than three cups of coffee a day during pregnancy nearly tripled the risk of miscarriage, Dr. Infant-Rivard said.
The researchers said the study supported the longstanding recommendation by the Food and Drug Administration, based largely on animal studies, that pregnant women curtail their caffeine consumption. Previous studies have reached different conclusions about the possible dangers of caffeine for pregnant women.
The new report conflicts with the conclusions of a study by Dr. James L. Mills and other researchers at the National Institute of Child Health and Human Development in Bethesda, Md. That study, which was reported in the journal in February, suggested that drinking three or fewer eight-ounce cups of coffee a day did not increase the risk of miscarriage or affect fetal development. Dr. Mills is on vacation, and efforts to reach him by telephone yesterday were unsuccessful. Reconciling Differences
In an editorial accompanying the study, Dr. Brenda Eskenazi of the University of California at Berkeley offered several possible explanations for the differing conclusions of the two studies.
"The accuracy of the exposure assessment is affected by the huge range of cup sizes and the considerable variability of caffeine content of coffee brewed by different women at different times and in different countries," Dr. Eskenazi wrote.
Caffeine from sources like tea, chocolate and soft drinks "may not have equally toxic constituents," Dr. Eskenazi wrote, adding that it might be that chemicals other than caffeine that are released during the roasting process, may be "the exposure of concern."
Dr. Infante-Rivard and her colleagues based their findings on interviews with 331 women who experienced miscarriages and 993 women who had normal pregnancies. The research was conducted at Sainte-Justine Hospital at the University of Montreal from May 1987 to November 1989.
"The bulk of the evidence from human and animal studies now suggests to us that it would be wise to reduce the intake of caffeine, certainly during pregnancy, and to err on the side of caution even before pregnancy," Dr. Infante-Rivard said. "I cannot recommend a safe level of consumption, because I don't think we know about that yet."
Also contributing to the study were Dr. Alberto Fernandez of McGill University, and Dr. Robert Gauthier, Dr. Michele David and Dr. Georges-Etienne Rivard, all of the University of Montreal.