A study of weight gain in the first year of life.

to growth during the first year of postnatal life. A majority of the babies (702) came from one private and two municipal welfare clinics in the city; the remainder (580) attended the Institute of Social Medicine. The latter are also enrolled in the Child Health Survey and are the subjects of a more intensive study of growth and development during the first five years of life (Thwaites, 1950). The babies attending the Institute of Social Medicine were seen for the first time at 4 weeks, and again at 3, 6, 9, and 12 months. The remainder were brought to the clinics at monthly intervals. Since the two municipal clinics were held in the same room but on different days, only three different weighing scales (balance type) were used. Four persons were responsible for the records, but each baby was supervised by the same person; they were weighed naked on the same scales, and the weight was recorded to the nearest whole ounce. Although the mothers often failed to bring their children on the appointed dates, in most cases the first visit, due at one month, did not vary by more than a week from the correct day, and those due at 3, 6, 9, and 12 months were rarely more than two weeks too early or too late. In the exceptional cases an estimated weight for the correct date has been obtained from a curve drawn through the five recorded weights. In the result, the weights used in this paper have been derived from actual weighing and from graphic estimation in the following proportions: