The intra-uterine growth of infants,estimated by the weights of pre- and post-maturely born infants

Abstract

It has been shown by Read 1 that the intra-uterine growth of the guinea-pig consists of one whole growth-cycle and a portion of a second, birth occurring during the progress of the second growth-cycle. The point of junction of these cycles is a critical period in the growth of guinea-pigs. The junction of the two cycles, at a period when growth is relatively slow, is not infrequently faulty and premature delivery of dead young occurs at this period much more frequently than at any other.

I have sought to ascertain whether or not a similar critical period occurs in the intra-uterine growth of infants. Through the courtesy of the matron, Miss E. C. Sketheway and of Dr. H. Gilbert, I have had access to the extensive and admirably kept records of “The Queen's Home,” a large maternity hospital in Adelaide, South Australia.

Reckoning the period of gestation from the date of onset of the last menstruation I find that there is no tendency whatever for premature deliveries, in pregnancies not accompanied by pathological conditions in the mother, to occur at any given period rather than at any other.

Plotting the frequencies of deliveries as ordinates and the corresponding periods of gestation as abscissae we obtain a normal unimodal frequency-curve, the mean period of gestation being 282.5 ± 0.55 days for 247 male infants and 284.5 ± 0.57 days for e64 females, whence it appears that females are born later than males, the probability of the truth of this conclusion being 142:1, 1

The weight of the infants at birth increases regularly with the length of the period of gestation. Plotting these weights as ordinates with the corresponding periods of gestation as abscissae the curve of growth thus obtained passes smoothly into the extrauterine curve of growth for South Australian infants, without any indication of a slackening of growth such as occurs at or near the junction of two growth-cycles.