CHANGES DURING PREGNANCY 545 



interesting suggestion that- the nausea ancl vomiting of early 

 pregnancy is related to this abnormal metabolic condition and can be 

 combated by an abundant supply of carbohydrates given at frequent 

 intervals. It is certainly suggestive that the "morning sickness" 

 occurs at that time of the day when there has been the longest 

 interval after a meal. This tendency of the normal pregnant organism 

 to acetonuria suggests further that at least some forms of the 

 pernicious vomiting of pregnancy, where large amounts of the acetone 

 bodies are excreted, are merely an aggravation, due to some toxic 

 factor, of this normal tendency. For we know from the occurrence 

 of the acetonuria following after chloroform or ether narcosis or in 

 some febrile conditions that some toxins are capable of inducing this 

 metabolic disturbance. 



The work of Bohr and of Lochhead and Cramer has shown the 

 importance of carbohydrates for the development of the foetus, in 

 Rodents at any rate. The facts referred to in this section indicate 

 that this holds good also for the human foetus. Pregnancy in the 

 human subject imposes such a drain of carbohydrate material from 

 the mother that for the maintenance of a normal metabolism a larger 

 supply of carbohydrate is necessary for the pregnant than for the 

 non-pregnant woman. 



The formation of these acid bodies in pregnancy naturally leads 

 to a discussion of the acid-base equilibrium in pregnancy. 



F. The Acid-base Eqioilihriurn in Pregnancy. The so-called 

 " Acidosis of Pregnancy " 



The question to be discussed here is whether the acid-base 

 equilibrium is disturbed in normal pregnancy by the excessive 

 formation of acid metabolites. The body tends to maintain at a 

 constant level the reaction of the blood or, as it is called, the 

 hydrogen-ion concentration of the blood. It can compensate for an 

 increased formation of acid bodies chiefly by the following three 

 methods : firstly, by an increased lung ventilation which leads to a 

 lowering of the alveolar COg pressure ; secondly, by a transformation 

 of the disodium phosphate excreted in the urine into the acid mono- 

 sodium phosphate; and thirdly, by combining acid with ammonia, 

 which would usually be converted into urea, and excreting the 

 ammonium salt in the urine. The criteria of an increased formation 

 of acid metabolites — a condition which is now usually designated 

 by the term " acidosis " — are therefore lowering of the alveolar COg, 

 the acidity of the urine, and the increased excretion of ammonia. 

 These three factors do not necessarily come into play simultaneously. 

 It should be also borne in mind that the conception of " acidosis " as 

 18 



