Caffeine and Miscarriages Link Stronger than ThoughtJan 21, 2008 | Parker Waichman LLP
Caffeine, never a good choice for pregnant women, could increase the risk of miscarriages more than previously thought. A new study has more definitively revealed that women in early pregnancy need only drink a cup and a half of coffee daily up their chance of miscarriage than those who avoid caffeine. The study was conducted by Kaiser Permanente out of Oakland and was published today in the American Journal of Obstetrics and Gynecology. This study is one of the largest of its kind to review the connection between caffeine and miscarriage and the first to interview women about their caffeine habits before actually suffering a miscarriage. There has been much research into caffeine and miscarriage—some dating back nearly 50 years—but, up until now, no studies have been definitive. Doctors who reviewed the information from the Kaiser study, but who were not involved in the research, said the findings make a strong case against drinking coffee, or any kind of caffeinated beverage, early in pregnancy. "I would probably not even recommend a cup a day, based on this. It's not a huge risk, but it's a real effect," said Dr. Aaron Caughey, a perinatologist at UCSF.
Despite the new findings, Caughey said it's important to note that the majority of miscarriages—up to 80 percent—happen as a result of chromosomal abnormalities that have nothing to do with the mother's behavior. The last thing women who have had miscarriages need to do is blame themselves, he said. "The data has been consistent, but the question has been whether this is a real effect or not," said De-Kun Li, a research scientist in Kaiser's Northern California division and an author of the paper. "Our study has addressed that issue. Hopefully that relationship is much more firmly established now," he added
Researchers interviewed 1,063 pregnant women; 16 percent had miscarriages. Women who consumed 200 mg of caffeine daily—about a cup and a half of coffee—were twice as likely suffer miscarriage than those who consumed less than 200 mg daily or those who had no caffeine at all. The difference in risk was most noticeable in miscarriages occurring after eight weeks of pregnancy. The study took into account age, alcohol consumption, smoking, and other factors related to miscarriage; the risk from caffeine remained. The study did not look at the effects of caffeine on pregnancies past 20 weeks. The theory is that caffeine passes easily from the mother, through the placenta, to the fetus, which is unable to metabolize the drug in a healthy way. Some believe that later in the pregnancy, as the baby's metabolic system matures, caffeine is safe.
The Kaiser study revealed a small and statistically insignificant increase in risk for women who consumed less than 200 mg of caffeine every day. But that includes a wide group of caffeine drinkers, doctors noted, and it's possible the women who drink, say, a cup of coffee—with roughly 150 mg of caffeine—increase miscarriage risk, while those who drink one soda—with 30 to 50 mg of caffeine—do not. "This is a little bit like the alcohol studies, where we are unable to say that any alcohol is safe," Caughey said.