To determine if caffeine intake before and during pregnancy was associated with an increased risk for fetal loss.Incidence-density case-control study.University-affiliated obstetric and pediatric hospital in Montréal, Québec.A total of 331 women with fetal loss and 993 controls with a normal pregnancy at the same period of pregnancy as the case.Crude and adjusted odds ratios (ORs) for fetal loss were estimated using conditional logistic regression. A trend test for increasing caffeine intake was also used.Caffeine intake was divided into quartiles; the baseline for comparison was less than 48 mg per day. The adjusted ORs for fetal loss associated with caffeine intake before pregnancy were 1.29 (95% confidence interval [CI], 0.85 to 1.95) for 48 to 162 mg; 1.37 (95% CI, 0.92 to 2.04) for 163 to 321 mg; and 1.85 (95% CI, 1.18 to 2.89) for more than 321 mg. The same comparisons were made for caffeine intake during pregnancy, and the respective adjusted ORs were 1.15 (95% CI, 0.82 to 1.63), 1.95 (95% CI, 1.29 to 2.93), and 2.62 (95% CI, 1.38 to 5.01). After controlling for confounding factors, there was a strong association of caffeine intake during pregnancy and fetal loss, compatible with a linear trend on the logistic scale in which ORs increased by a factor of 1.22 (1.10 to 1.34) for each 100 mg of caffeine ingested daily during pregnancy.Caffeine intake before and during pregnancy was associated with an increased risk of fetal loss, supporting the US Food and Drug Administration recommendation to pregnant women, largely based on animal studies, to reduce their caffeine intake.