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A population-based study of early spontaneous abortion in Sweden found that the risk of miscarriage increases with increased caffeine intake, according to a recent New England Journal of Medicine article.
Researchers conducted a population-based, case-control study of early spontaneous abortions in 562 women who had spontaneous abortion at six to 12 weeks gestation and 953 women who did not have spontaneous abortions who were matched to the case patients according to the week of gestation. Researchers interviewed women about their caffeine intake. Plasma cotinine was measured as an indicator of cigarette smoking and fetal karyotypes were determined from tissue samples. Multivariate analysis was used to estimate the relative risks associated with caffeine ingestion after adjusting for cigarette smoking and symptoms of pregnancy such as nausea, vomiting, and fatigue. Results show that:
• Among nonsmokers, more spontaneous abortions occurred in women who ingested at least 100 mg of caffeine per day than in women who ingested less than 100 mg per day.
• Risk of spontaneous abortion increased with increased caffeine intakes with an odds ratio of 1.3 for women who ingested between 100 and 299 mg of caffeine per day; an odds ratio of 1.4 for women who ingested between 300 and 499 mg of caffeine daily, and an odds ratio of 2.2 for women who ingested 500 mg of caffeine or more daily.
• Among smokers, caffeine ingestion was not associated with an excess risk of spontaneous abortion.
• When the analyses were stratified according to results of fetal karyotyping, ingestion of moderate to high levels of caffeine was associated with an excess risk of spontaneous abortion when the fetus had a normal or unknown karyotype, but not when the fetal karyotype was abnormal.
[See: Cnattingus S, Signorello LB, Anneran G, et al. Caffeine intake and the risk of first trimester spontaneous abortion. New Engl J Med 2000; 343(25):1839-1845.]