CHANGES DURING PREGNANCY 535 



Murlin has pointed out that some of the high ammonia indices 

 obtained in eclampsia and also in normal pregnancies are due to 

 decomposition occurring in the bladder, when a catheter has been 

 used. Even with the strictest aseptic precautions it is impossible to 

 prevent a plug of mucus being pushed into the bladder. Catharsis is 

 another factor which may raise the ammonia index considerably by 

 temporarily lowering the nitrogen intake. 



There is no doubt that in abnormal pregnancies, particularly in 

 the pernicious vomiting of pregnancy, there is an actual increase both 

 in the relative and in the absolute amounts of ammonia excreted. 

 The ammonia index may rise to 30, 40 and even 70 against the 

 normal index of 4 to 8. But this condition necessarily involves a low 

 nitrogen intake which may amount to starvation. This in itself 

 raises the ammonia index. In addition, there is frequently, if not 

 always, a formation of considerable amounts of aceto-acetic acid and 

 oxybutyric acid which lead to an increased excretion of ammonia and 

 thus raise the ammonia index. It has been suggested that the high 

 ammonia excretion is due primarily to a faulty protein metabolism 

 which is specific for pregnancy. But the formation of the acetone 

 bodies is in itself an adequate explanation of the increased ammonia 

 excretion, and it is difficult to understand why so many observers 

 refuse to attach any importance to the presence of these substances. 

 It is even more difficult to understand why some workers have carried 

 this neglect so far that they record long tables of analyses for the 

 nitrogen distribution of the urine which show exceptionally high 

 values for the ammonia index and completely omit even to test 

 qualitatively for the presence of the acetone bodies. The only 

 observations which have paid due attention to this point are those of 

 Gilliatt and Kennaway 1 who found a close parallelism to exist 

 between the amount of the acetone bodies present and the ammonia 

 excretion. The amount of acetone bodies present in their cases was 

 too high to be accounted for as a direct result of starvation. The}' 

 are inclined to look upon the excessive formation of these bodies as 

 the primary cause of the condition, and draw an analogy with the 

 similar conditions of cyclic vomiting in children. The point is of 

 some practical importance, because a persistent high ammonia index 

 is regarded by many authorities as an indication for emptying the 

 uterus. The ammonia index can only be determined by a skilled 

 worker in a special laboratory, and for its proper appreciation requires 

 a knowledge of the total nitrogen intake of the patient, i.e. a collection 

 of the urine excreted for twenty-four hours. A good estimate of 



1 Gilliatt and Keunaway, " Some Observations upon Cases of Vomiting in 

 Pregnancy," Quar. Jour. Medicine, vol. xii., 1918. This paper contains also a 

 critical survey of the literature on the metabolism in this condition. 



