Studies of caffeine and theophylline in the neonate.

About 50% of 327 umbilical cord sera from infants born at the Medical Center Hospital of Vermont contained 1.0 microgram/ml or more of caffeine; about 25% contained equivalent concentrations of theophylline. Cord concentrations of caffeine greater than 3.0 micrograms/ml were associated with a significantly increased incidence of birthweights greater than 4 kg and a decrease in the incidence of 1-minute Apgar scores of less than seven. Cord blood caffeine concentrations of 69 infants born in Marburg, West Germany had a mean of 1.6 micrograms/ml, with 64% greater than 1 microgram/ml. Caffeine accumulated in the serum of infants treated with aminophylline for apnea of prematurity, apparently from methylation of theophylline.