Since the introduction of the glucose tolerance test as a diagnostic aid the glucose has-classically been administered by mouth. By this procedure the pregnant women may exhibit a normal tolerance to glucose or may in many instances exhibit a decreased tolerance to glucose (1-4). Selman (3), for instance, reports 22 out of 47 patients studied by him to show high, prolonged or high and prolonged blood glucose levels when judged by certain criteria. Hurwitz and Jensen (4) find normal fasting blood sugar levels and normal peaks, but 81 per cent of their pregnant series showed high blood sugar values at two hours. From these data these authors conclude that pregnancy exerts a deleterious effect on carbohydrate metabolism.The disadvantages of the oral route of administration of the glucose are many and they have been pointed out by several authors (5-9). These disadvantages have led to the use of the intravenous route of administration (8, 9) as a better test of the ability of the subject to metabolize glucose. In pregnancy all the objections to the oral route of administration apply as they do in the nonpregnant individual. In addition, alterations in the gastrointestinal tract peculiar to pregnancy might complicate the picture further.In view of these considerations we have determined the tolerance of pregnant women to intravenously administered glucose. The over-all procedure employed is essentially the same as the one described by Lozner, Winkler, Taylor and Peters (9) who have determined the tolerance of nonpregnant individuals to 25 grams of intravenously administered glucose. SUBJECTS AND METHODSSubjects were chosen from the obstetrical in-patient and out-patient services of the New York Hospital. Only 1 This study was aided by a grant from the John and Mary R. Markle Foundation, women whose course and past history were considered normal were chosen. Individuals with histories of previous glycosuria, or current diabetes, hypertension, kidney or liver disease were eliminated. The tests were performed on subjects at various stages of pregnancy. Subjects for control study were chosen from gynecological in-patients. They were all within the child-bearing age.Only those with benign conditions were selected.There were 20 in the pregnant group. Their ages ranged from 17 to 43 years with an average age of 28.9 years. There were five in the fourth, three in the fifth, two in the sixth, three in the seventh, three in the eighth, one in the ninth, and three in the tenth lunar month of pregnancy. There were 11 in the non-pregnant group. Their ages ranged from 20 to 38 years with an average age of 28.9 years.All subjects were in the post-absorptive state. Some were encouraged to drink 600 to 800 ml. of water before the test was started in order to promote urine flow. A No. 18 Foley indwelling catheter with a 5-ml. bag was placed in the bladder and the bladder emptied. A blood sample was withdrawn. Then 50 ml. of 50 per cent glucose were injected intravenously through a No. 18 needle in 45 to 60 seconds. Blood samples were ...