The 3 hour GTT

Hooray!! I don’t have gestational diabetes!  Such a relief!

I spent my Sunday morning with the nice folks at the lab.  This time, for the 3 hour glucose tolerance test, I was given more specific instructions.  I had to have half a sandwich and a glass of milk between 10 pm and midnight, and then come in for my fasting blood draw between 8 and 10 hours of fasting.  Since the lab opened at 8:30 am on Sunday, that means I had to eat my sandwich at the earliest at 10:30 pm.  So I had to stay up past my usual bedtime to have the sandwich and milk.  I did soy because I can’t stand the thought of drinking regular milk, even since pre-pregnancy.  And soy is closer than almond milk in terms of content.  I don’t know the exact reasons for the instructions, but I didn’t want to vary too much in terms of sugar, protein, and fat content in case it mattered.  It felt kinda gross to then go to bed shortly after, but oh well.

Surprisingly, I wasn’t starving by the time I got to the lab.  They drew my fasting level, then gave me another 10 ounces of artificial orange, except this time with 100 grams of glucose.  I then proceeded to wait in the waiting room reading magazines and such as I had my blood drawn each hour for 3 hours.  They want you to remain seated for the most part, because you can imagine if you’re running around during the test, you’d falsely lower your blood sugars.  Same reason that normally it’s good to walk around after a meal.

Monday morning, I got the results- all 4 normal values!  If you have 2 or more high values, then you’d be diagnosed with gestational diabetes mellitus (GDM).  I did notice that compared to the 1 hour test, I felt better.  Presumably because my blood sugars weren’t high.  Which makes me relieved that despite my regular carb and sugar intake, my blood sugars probably haven’t been climbing abnormally high.  Given my eating issues and feeling sick throughout the pregnancy, I’m just so relieved, because it would have been VERY painful to have to be super careful with my eating habits if I were diagnosed with gestational diabetes.

I was upset after seeing the abnormal 1 hour result, in part because like any other patient, it’s upsetting to see an abnormal value.  But also, I knew immediately that even if I weren’t diagnosed with GDM, I’d be labeled with “glucose intolerance,” suggesting that my body has some hardship processing sugar, and therefore conferring some elevated risk for diabetes in the future (just not as high as if I had overt GDM).  Now, I’m not sure if that’s really the case.  I don’t know if my Paleo lifestyle pre-pregnancy somehow affected this test.  My parents were born and raised in Japan, and despite my urging for them to go Paleo, at least partway, they have continued to eat rice and noodles all their lives.  My mom is 66 and my dad is 71, and neither of them have diabetes, so I figured I probably wouldn’t be that susceptible.

Ultimately, the testing for GDM is a screening tool.  As painful as it is for women like me to get that abnormal 1 hour result and have to endure the 3 hour test with 4 needle sticks, it helps catch more women with GDM.  Which is better than missing a bunch.  Now, there’s a reason I didn’t go into academic medicine and I don’t care to scour the studies behind all of this.  But there are different methods of screening for GDM.

My particular institution, like most places in the US, does the two-step testing with the 1 hour test and the 3 hour confirmatory test.  According to the ACOG Practice Bulletin on gestational diabetes, some experts have proposed a one-step two hour test.  It involves a fasting draw, a 75 gram oral glucose load, then drawing blood at one hour and two hours later.  The reason why this hasn’t been accepted widely is that it was thought that it would increase healthcare costs without a significant improvement in maternal or newborn outcomes.

Some have proposed lowering the values for an abnormal 1 hour test.  This would pick up some more gestational diabetics, but that also means a lot more false-positives.  Which means more unhappy women like myself who have to endure the 3 hour test.  Ultimately, no test is ever perfect, and they try to find the best balance of appropriate sensitivity at picking up the disease, without an undue burden of false-positives and health care costs.

Despite my unhappiness at having to go through this process, I know how important it is to diagnose GDM appropriately.  Bottom line is that untreated GDM is bad for baby and mom.  And like many aspects of this pregnancy, it also helps me as a clinician to have gone through the 3 hour test and know what it’s like to experience it.