According to The US National Library of Medicine: "For this test you will drink a glass of water that contains 50 grams of dissolved sugar. You do not need to fast beforehand. One hour later, blood will be taken from a vein in your arm to determine the blood sugar level. If the value is below 7.5 millimoles per liter (mmol/L, about 135 mg/dL), the results are considered normal and no more testing is done.
If an elevated level is found in the glucose challenge test, it is still not considered a final diagnosis. It only serves to determine which women will be offered a second and final test. This second test, called the oral glucose tolerance test, is more involved. For the test, the pregnant woman must fast beforehand, which means not eating or drinking anything but water for at least eight hours. The first step in this test is taking blood. After this the woman drinks a sugar solution containing 75 grams of glucose. Blood is taken from an arm vein again after one hour and after two hours. If any of the following three blood sugar values is exceeded, gestational diabetes will be diagnosed:
- After fasting: 5.1 mmol/L (92 mg/dL)
- After one hour: 10.0 mmol/L (180 mg/dL)
- After two hours: 8.5 mmol/L (153 mg/dL)"
According to pregnancy.com:
"One of the most intriguing recommendations is that a woman may not need laboratory testing to screen for GD if she meets all of the following criteria:
- less than 25 years old
- not a member of a racial or ethnic group with a high prevalence of diabetes (eg, Hispanic, African, Native American, South or East Asian, or Pacific Islands ancestry)
- a body mass index (BMI) 25
- no history of abnormal glucose tolerance
- no previous history of adverse pregnancy outcomes usually associated with GDM
- no known diabetes in first-degree relative
Women who are at a higher risk for GDM usually have one of the following risk factors:
- family history of diabetes
- past obstetric history"
Before testing, you should eat normally for the few days prior. Women used to be told to eat less carbs or sugar in the days before their test, but that could just make your body react more aggressively to the glucose in the drink, giving a false higher result. If you are opposed to drinking loads of sugar water and various other chemicals, you can arrange to eat a specific breakfast and have your blood drawn at an interval following your meal instead. Many doctors frown upon such a request, but it is your right to request it.
My own experience and advice for others that are deemed "borderline" like I was: I demanded a retest and that one came back ok but they were "concerned", so I compromised and told them I'd do my best to follow a GD diet and I'd monitor my sugars for a couple of weeks to "put their minds at ease". I figured I could use healthy eating guidelines anyway (though I did still have my daily vanilla ice cream cone) and when monitoring was all good, they left me alone. They insisted I get urine/ketosis sticks and keep a food log which I was meant to fax to them, but I did neither because EFF THAT, THEY'RE NOT MY MOMMA.
I had a bit of a rebellious streak during my pregnancy as you can tell ;) But honestly, I think it's a fair compromise and it'll give you AND the doctors a chance to see how your sugars are doing in the real world over time, rather than just once during a lab test. And then I think no matter what happens, everyone will have peace of mind that they're making the right decision on how to proceed; whether your sugars really ARE high or not. This was something I did in order to appease my doctors because I had one slightly elevated level on my test but otherwise showed no symptoms, but you can also request to have this several-times-a-day self-monitoring in place of the glucose challenge. Again, your doctor might fight you on this request, but as I mentioned previously, this is the best way to get a REAL WORLD view of your glucose metabolism, which is much more accurate than a one-time lab setting.
In the next last post on GD, I will discuss the various ways that Gestational Diabetes can be treated if you are, in fact, diagnosed with GD after your tests.