Week 23… less than four months until our due date. I am trying very hard to suppress the urge to turn J’s “man cave” (the office/den) into the nursery. We both know it will happen in due time, but I am hoping to put it off for as long as my biological instincts will permit.
My belly is now large enough that my pregnancy is obvious to strangers. This afternoon, we stopped into H&M to have a peek at the maternity section, and from about 20 feet away, a store employee called out to me to let me know that the maternity wear had moved to a different part of the store. Last time I was there (about a month ago), when I tried on and subsequently purchased several pieces of maternity clothes, both the change room attendant and the cashier looked at me quizzically and asked if I was actually pregnant.
Now, on to the topic of gestational diabetes testing. First of all, it must be explained that pregnancy causes women to become slightly insulin resistant, similar to a type II diabetic, but to a lesser degree. This is an evolutionary mechanism that facilitates the transfer of nutrients from the mother to the fetus, since the fetus will be more sensitive than the mother to the effects of the storage hormone insulin. This in and of itself is not problematic, but keeping in mind that most pregnant women are already eating a fairly high carbohydrate diet, and then often using pregnancy as an excuse to indulge, the high prevalence of GD is hardly surprising.
The most commonly-used initial screening for GD is the one-hour glucose tolerance test (GTT), which involves consuming a sugary drink containing 50 grams of glucose within a five minute period, and then testing blood sugar levels one hour post-consumption. Even amongst women who eat a standard 60 percent or higher carbohydrate diet, the side effects of this intense sugar rush may include nausea, dizziness, elevated heart rate and hypoglycemia. For a woman who has been eating a low-carb or Paleo style diet, and whose body is largely accustomed to burning fat for fuel, it is extremely likely that the body will have difficulty processing such a large infusion of sugar. In my research, I have come across numerous accounts of healthy, Paleo-adherent women with no prior pregnancy complications who falsely screened positive for GD.
It seems silly, doesn’t it, to test a woman for her tolerance to something that she simply doesn’t consume in the course of her daily life. But it actually gets worse: if a woman screens positive for GD, she is then administered the three-hour GTT, which involves consuming a high-carbohydrate diet for three days, fasting overnight, ingesting 100 grams of glucose (yes, double the amount of the previous test) and then having her glucose levels measured at various intervals over a three-hour period. Chances are that a woman who has difficulty processing 50 grams of glucose in one go is probably not going to do much better with 100 grams!
With all that in mind, we discussed our concerns about the GTT with our midwife, and she proposed an alternative: the two-hour postprandial glucose test. This test involves an overnight fast followed by the patient’s typical morning meal, and then a test of glucose levels exactly two hours after the meal. So instead of testing the body’s processing of an uncharacteristically large amount of sugar, this test measures the blood sugar response to a normal, typical meal. We also had the option to decline glucose testing altogether, but given that I have the GD risk factor of a family history of diabetes (both type I and type II), the midwife suggested it would be prudent to take the test. Thus, I will undergo the postprandial glucose test somewhere between 24 to 26 weeks.
Other alternatives to the one and three-hour GTT include the HbA1c test (which shows mean glucose levels over an eight to 12 week period), and using a glucometer to test at home several times per day over a one or two week period.
If you are interested in some slightly more scientific explanations about gestational diabetes, pregnancy blood glucose levels, and testing methodologies, Robb Wolf has a couple of great posts on his blog: