September 28, 2007
Gestational Diabetes
Question from San Diego, California, USA:
I was tested for the gestational diabetes at 21 weeks and the one hour reading came back at 149 mg/dl [8.3 mmol/L]. They said I missed the cut off by 9 points, so I was instructed to come back and do the three hour test the following week. I was told to fast from midnight until my 8 a.m. appointment. I arrived and they tested my blood with a fingerstick and my reading was 68 mg/dl [3.8 mmol/L], below the normal of 70 mg/dl [3.9 mmol/L] to 90 mg/dl [5.0 mmol/L]. I then drank the glucose and had blood drawn once every three hours. My results came back and everything was in the normal ranges. They did not give me the numbers, just said all was okay. So, I then had a few more visits and was told nothing again about the gestational diabetes test. Now at 29 weeks, they want me to retake the three hour test because I failed the one hour test. I asked why as I had done the three hour and my results were all normal. Their reasoning was because I could still develop diabetes and I was screened early. There is no point in doing a one hour and failing it again and then having to do the three hour test so they want me to go straight to the three hour again. I am a little confused because the nutritionist said that she does not understand why, if my results were normal. And, as the nurse and the nutritionist discussed it, the nurse practitioner got real defensive. So, I told them I would call them back because I am paying for this pregnancy myself and I could not afford it at the time. But, I really wanted another opinion about whether or not I really need to do the three hour test for the second time?
Answer:
If all of the three hour values are normal, then you are not obligated to repeat the screening. However, since the initial 50 gram screening test was abnormal (I use 135 mg/dl [7.5 mmol/L] as a cut off), there is an increased risk of developing gestational diabetes later in the pregnancy. Your doctor could be less inclined to repeat the testing if it appears that the baby is not growing faster than expected. Babies of mother’s with diabetes tend to be big. Another option would be to check a fasting blood glucose and a one or two hour postmeal glucose level. Your fasting values should be 70 mg/dl [3.9 mmol/L] to 90 mg/dl [5.0 mmol/L]; at one hour after a meal, the glucose should be less than 130 mg/dl [7.2 mmol/L]; and at two hours afterwards, it should be less than 120 mg/dl [6.7 mmol/L]. This is not a formal screening method, but does reflect your eating habits. It may be cheaper than paying for the three hour testing. If any of these values are elevated, then you could move on to dietary counseling and continued glucose monitoring.
OWJ
