The association between low birth weight and caffeine consumption during pregnancy.

In a prospective study of 3,891 antenatal patients at Yale-New Haven Hospital between 1980 and 1982, 76.7% consumed caffeine from coffee, tea, colas, and drugs. A dose response of caffeine intake to increased risk for delivering low birth weight (less than 2,500 g) singleton newborns was observed. This relation was observed in deliveries after 36 weeks gestational age. When comparison was made with women who had no caffeine exposure, the relative risks of low birth weight after adjustment for confounding factors were 1.4 (95% confidence interval (CI) 0.7-3.0) for 1-150 mg of caffeine daily; 2.3 (95% CI 1.1-5.2) for 151-300 mg; and 4.6 (95% CI 2.0-10.5) for over 300 mg. Decreases in mean birth weight were 6, 31, and 105 g, respectively. Gestational age did not appear to be related to caffeine consumption in the crude or adjusted analysis. Maternal caffeine intake seems to exert an effect on birth weight through growth retardation in term newborns.