Effect of caffeine exposure during pregnancy on birth weight and gestational age.

Epidemiologic studies have been unable to conclusively evaluate whether caffeine intake during pregnancy is associated with reduced birth weight and/or fetal growth restriction. The authors conducted a prospective, population-based cohort study to investigate the effect of caffeine on birth weight, gestational age, and birth weight standardized for gestational age (birth weight ratio). Of 953 women recruited in early pregnancy in Uppsala County, Sweden, from 1996 to 1998, 873 women delivering liveborn singleton infants were included in the analysis. Caffeine exposures were ascertained from in-person interviews at 6-12 and 32-34 completed gestational weeks, and maternal plasma was analyzed for cotinine levels as an indicator of smoking. Analysis of variance was used to estimate the effect of caffeine on birth weight, gestational age at delivery, and birth weight ratio after accounting for the effects of other covariates, such as maternal sociodemographic characteristics, plasma cotinine, and pregnancy symptoms. There were no associations between caffeine consumption and birth weight, gestational age, and birth weight ratio, neither when caffeine exposure was averaged from conception to the 32nd to 34th gestational weeks, nor when caffeine exposure was stratified by trimesters of pregnancy. These results do not support an association between moderate caffeine consumption and reduced birth weight, gestational age, or fetal growth.