The problems involved in breast feeding have been studied long and exhaustively and there remains little to be said on the subject. There is one point, however, on which medical writers are indefinite, that is, the length of time which a baby should be allowed to stay at the breast at each feeding.
Twenty minutes at each nursing is usually taught as an absolute rule to nurses and physicians, and by them transmitted to the mother. This tradition has been handed down from generation to generation and is seldom questioned.
Few textbooks mention definitely the nursing time, merely stating that it should not be prolonged beyond 20 minutes, and that often from ten to fifteen minutes will suffice. Many authors state that the baby may nurse until satisfied or sleepy. A few hint at what we have found to be the real facts, but are not sufficiently definite.
SMITH CH, MERRITT KK. THE RATE OF SECRETION OF BREAST MILK. Am J Dis Child. 1922;24(5):413-426. doi:10.1001/archpedi.1922.04120110054007