The post-natal loss of weight in infants and the compensatory overgrowth which succeeds it

Abstract

As stated in the preceding communication, it is possible, by plotting the weights of infants born somewhat before the expiry of the mean term of gestation against the length of the period of gestation, to obtain a curve of intra-uterine growth which continues without any break or any period of loss of weight into the normal curve of extra-uterine growth. It represents the continuation of this latter curve backwards from the time of birth. In the same way, plotting the weights of children born somewhat later than the average term, we obtain a curve which is identical with and overlies the normal curve of extra-uterine growth for the period which it covers. By combining these various data a continuous curve of intra- and extra-uterine growth is obtained without any interruption due to the post-natal loss of weight which normally occurs during the first week after birth. From this we can readily estimate what would be the average rate of growth in an infant during its first two weeks of extra-uterine life were it not for the shock due to birth. For South Australian male infants I find that the gain during the first week following birth should be six ounces, during the second seven ounces. But the average male infant in South Australia actually weighs 6.2 ounces less at one week than it did at birth. Since it should have weighed 6 ounces more than it did at birth the true loss of weight due to birth is 12.2 ounces which is 9 per cent. of its weight at birth. At the end of the second week of extrauterine growth the average South Australian male infant weighs 3.4 oz. more than it did at birth, but since it should have gained 13 oz. since birth the loss of weight due to birth is now 9.6 oz.