We are much indebted to Dr. Whitridge Williams of Baltimore, and his assistants, who have demonstrated, to some extent at least, the nature of the disturbances of metabolism which cause a peculiar toxemia, and pernicious vomiting during pregnancy. Chemical examination of the urine in such cases shows a decrease in the amount of nitrogen excreted as urea, and an increase in the amount excreted as ammonia. Without referring to other changes we may accept the fact that this excess of ammonia excreted, or, as it is called, the ammonia coefficient, furnishes a fair indication of the severity of the poisoning. In normal pregnancy it is 4 or 5 per cent., and in cases of toxemia may rise to 10, 20, 40 per cent., or even higher. Dr. Williams has expressed the opinion that if this ammonia coefficient exceeds 10 per cent., the patient's life is endangered, and the pregnancy should be
WRIGHT AH. PERNICIOUS VOMITING OF PREGNANCY. JAMA. 1910;LIV(19):1503–1504. doi:10.1001/jama.1910.92550450001001h
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