The relation of the mother's use of alcohol during breast feeding to the infant's development at one year of age has been investigated in 400 infants studied in the Department of Epidemiology, University of Michigan, Ann Arbor, Department of Epidemiology and Pediatrics, University of Washington, Seattle. Mental development, as measured by the Bayley Mental Development Index, was unrelated to maternal drinking during breast-feeding. However, motor development, as measured by the Psychomotor Development Index, was significantly lower in infants exposed regularly to alcohol in breast milk with a dose response relation. 
COMMENT. Nursing mothers can no longer enjoy a glass of beer as a prescribed method for sedating a sleepless baby without risking a detrimental effect on the infant's development. The practice of offering the parents a complimentary dinner with champagne at the time of discharge from maternity units will have to cease, or if continued, with moderation and caution. It may be argued that the results of this study are suggestive but the detrimental effects on the development are not sufficiently severe to be clinically important for the individual child. The finding that the mental development of infants exposed to alcohol through breast feeding was not affected is of interest and might be explained by the timing of the exposure and the age at which the child was tested.