Because of my family history, I elected to have a glucose tolerance test (100 gm) early in my pregnancy (15th week). The results are as follows:

Fasting 4.78 mmol/l (86 mg/dl); 1st hour 11.20 mmol/l (201 mg/dl); 2nd hour 8.68 mmol/l (156 mg/dl); 3rd hour 5.82 mmol/l (104 mg/dl).

Given the above, do I have gestational or pre-existing diabetes?

On your test, only the first hour value is elevated. Normal is less than about 10.6 mmol/l (190 mg/dl). You must have at least two abnormal values to meet the criteria for gestational diabetes. However, it may be worthwhile to repeat the three hour test between 24 and 28 weeks since gestational diabetes is more likely to develop during this time. Based on this test, you do not have pre-existing diabetes.

Addendum

This question was originally answered using older criteria for the diagnosis of gestational diabetes. Based on recent guidelines from the American Diabetes Association, both the one hour and two hour blood sugars exceed the threshold. The upper limits are fasting of 95 mg/dl (5.3 mmol/l), one hour of 180 mg/dl (mmol/l), two hour 155 mg/dl (8.6 mmol/l) and three hour of 140 mg/dl (7.8 mmol/l). Since this test is positive relatively early in the pregnancy, then there is the possibility of preexisting diabetes and a screen after the pregnancy is over would be worthwhile. With a normal fasting and just a slightly elevated second abnormal glucose, diet therapy may be adequate.

OWJ