Background: Caffeine is a widely used and accepted pharmacologically active substance. The effect of caffeine intake during pregnancy on fetal growth and development is still unclear. Objective: We examined the associations of maternal caffeine intake, on the basis of coffee and tea consumption, with fetal growth characteristics measured in each trimester of pregnancy and the risks of adverse birth outcomes. Design: Associations were studied in 7346 pregnant women participating in a population-based prospective cohort study from early pregnancy onward in the Netherlands (2001-2005). Caffeine intake in the first, second, and third trimesters was on the basis of coffee and tea consumption and was assessed by questionnaires. Fetal growth characteristics were repeatedly measured by ultrasound. Information about birth outcomes was obtained from hospital records. Results: We observed no consistent associations of caffeine intake with fetal head circumference or estimated fetal weight in any trimester. Higher caffeine intake was associated with smaller first-trimester crown-rump length, second- and third-trimester femur length, and birth length (P for trend <0.05). Offspring of mothers who consumed >= 6 caffeine units/d tended to have increased risks of small-for-gestational-age infants at birth. Conclusions: Our results suggest that caffeine intake of >= 6 units/d during pregnancy is associated with impaired fetal length growth. Caffeine exposure might preferentially adversely affect fetal skeletal growth. Further studies are needed to assess these associations in non-European populations and to assess the postnatal consequences. Am J Clin Nutr 2010;91: 1691-8.