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January 7, 2006

Gestational Diabetes

Question from Manila, Philippines:

I'm 35 weeks pregnant today. I first had an Oral Glucose Tolerance Test (OGTT) in my 33rd week and failed two out of three tests. I just had my second OGTT test today to confirm the first and I failed two tests. My results, after a 100 gram glucose load are: fasting -- 73 mg/dl [4.1 mmol/L]; one hour -- 178 mg/dl [9.9 mmol/L]; two hours -- 182 mg/dl [10.1 mmol/L]; and three hours -- 78 mg/dl [4.3 mmol/L]. Here, in the Philippines, the normal ranges are: fasting -- 70-105 mg/dl [3.9 to 5.8 mmol/L]; one hour -- 90 to 155 mg/dl [5.0 to 8.6 mmol/L]; two hours -- 75 to 120 mg/dl [4.2 to 6.7 mmol/L]; and three hours -- 70 to 105 mg/dl [3.9 to 5.8 mmol/L]. I was scanning your web site and noticed that using your normal ranges, I would not have gestational diabetes, but using our Philippine ranges I do. With these results, do you think I have gestational diabetes? I have also been monitoring my blood sugar using a plasma set for the past 10 days and my blood sugars are always low one to two hours after a meal (105 mg/dl [5.8 mmol/L] average, sometimes even lower). I'm so worried about my baby, and also if my sugar is becoming too low because I may be overreacting avoiding carbohydrates and sweets.

Answer:

The values for the three hour glucose test that I use are derived from data from Dr. Coustan, a high risk pregnancy specialist with a strong interest in diabetes research. These values are recommended by the American College of Obstetrics and Gynecology. These are threshold values. There is not a range. Thus, if you exceed two or more values than you are diagnosed with gestational diabetes.

The fasting value is 95 mg/dl [5.3 mmol/L]; one hour is 180 mg/dl [10.0 mmol/L]; two hours is 155 mg/dl [8.6 mmol/L]; and three hours is 140 mg/dl [7.8 mmol/L].

In your test results, you only exceeded the two hour threshold. Therefore, you do not meet the criteria for gestational diabetes, at least by American standards. This is supported by your postmeal glucose values being in the normal range (105 mg/dl [5.8 mmol/L] is not too low and will not have any effect on the baby).

OWJ