Intra-uterine Growth of Infants. 



65 



Abstracts of the Communications, Pacific Coast Branch 



Sixth meeting. 

 43 (975) 



The intra-uterine growth of infants, estimated by the weights of 

 pre- and post-maturely born infants. (Preliminary 

 Communication.) 



By T. Brailsford Robertson. 



[From the Rudolph Spreckels Physiological Laboratory of the Univer- 

 sity of California.] 



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 infre- 

 quently 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 patho- 

 logical 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 =t °-57 days for 

 264 females, whence it appears that females are born later than 



1 J. Marion Read, Arch.f. Entwicklungsmech. der Organismen, 35 (1912), p. 708. 



