Coffee consumption and risk of hospitalized miscarriage before 12 weeks of gestation

In order to analyse the association between drinking coffee in pregnancy and risk of spontaneous abortion, a case-controlled study was conducted in Milan, Northern Italy. Cases were 782 women with spontaneous abortion within the 12th week of gestation. The control group was recruited from women who gave birth at term (> 37 weeks gestation) to healthy infants on randomly selected days at the same hospitals where cases had been identified: 1543 controls were interviewed. A total of 561 (72%) cases of spontaneous abortion and 877 (57%) controls reported coffee drinking during the first trimester of the index pregnancy. The corresponding multivariate odds ratios of spontaneous abortion, in comparison with non-drinkers, were 1.2, 1.8 and 4.0, respectively, for drinkers of 1, 2 or 3, and 4 or more cups of coffee per day. No relationship emerged between maternal decaffeinated coffee, tea and cola drinking in pregnancy, as well as paternal coffee consumption, and risk of spontaneous abortion. With regard to duration in years of coffee drinking, the estimated multivariate odds ratios of spontaneous abortion were, in comparison with non-coffee drinkers, 1.1 (95% confidence interval (CI) 0.9-1.4) and 1.9 (95% CI 1.5-2.6) for women reporting a duration of coffee consumption < or = 10 or > 10 years. In conclusion, coffee drinking early in pregnancy was associated with an increased risk of abortion. This has biological implications, but epidemiological inference on the causality is difficult and still open to debate.