CHANGES DURING PREGNANCY 555 



I. Summary of Clwnges in the Metabolism of Pregnancy 



The maternal organism adapts itself to the progressively increasing 

 requirements of the foetus, which dominate the metabolism of the 

 mother. Under suitable dietary conditions this adaptation is so suc- 

 cessful that the maternal organism completes pregnancy with a gain. 

 The dietary conditions which must be observed more particularly are 

 an abundant supply of firstly carbohydrates, secondly calcium, and 

 thirdly vitamins. The gain at the end of pregnancy is a reserve for 

 the mother to draw upon during the puerperium and lactation. 

 Under unsuitable dietary conditions the mother suffers first. 



The adaptation of the maternal organism involves changes in the 

 metabolism of the mother, of which the most definitely established i& 

 the occurrence of an acidosis due probably to the slightly increased 

 formation of aceto-acetic acid and oxybutyric acids. Under normal 

 conditions this acidosis remains within physiological limits and, like 

 the acidosis which sets in as the result of exposure to high altitudes, 

 it subserves the function of increasing the ventilation of the lungs. 

 Many facts point to the maternal liver as the organ on which 

 pregnancy imposes a special strain and this is confirmed by a hyper- 

 trophy of this organ occurring in pregnancy. 1 But no clear evidence 

 has yet been brought that normal pregnancy involves a hepatic 

 insufficiency. 



K. Analogy between the Metabolism of Pregnant Animals and 

 Tumour- Bearing Anim als 



Certain changes in the maternal organism, for instance those due 

 to the changes in the mamma and uterus, are obviously specific to 

 pregnancy. Others, however, are apparently simply the result of the 

 presence of a mass of rapidly growing cells in an adult organism. 

 For as Cramer 2 has pointed out, the metabolism of tumour- bearing 

 animals presents a close similarity to that of pregnant animals. 

 There is in both cases an increased nitrogen retention 3 which is in 

 excess of that necessary for the mass of growing cells and thus 

 benefits the organism serving as a host. There is the same faculty in 

 both cancerous cells and embryonic cells of being able to build up 

 living protoplasm with less nitrogen than the non-growing or more 

 slowly growing cells of the adult host. There is an increased demand 



1 Herring, "The Effect of Pregnancy upon the Size and Weight of some 

 of the Organs of the Body," Brit. Med. Jour., llth December 1920. 



2 Cramer, "Zur Btochemie des Wachstums," VIII. Interned. Physiologen 

 Konqress, Vienna, 1910. Also ///. Sci. Report, Imperial Cancer Research Fund, 

 19u8. 



3 Cramer and Pringle, " Contributions to the Biochemistry of Growth," Proc* 

 Roy. Soc., B., vol. Ixxxii., 1910 ; vol. Ixxxvi., 1912. 



