Glad I could help. Interestingly, the original "gestational diabetes" studies weren't about pregnancy per se at all. The researchers back in the 50s and 60s were looking for predictors of what is now called Type II diabetes and was then called "Adult Onset" diabetes and reasoned that since pregnancy was a stressor, it might reveal a predisposition to Type II. Women could then be advised of their risk and take proactive measures. They were right. It did predict later development of diabetes but only because high BMI women were more likely to have sub-diabetic high blood-sugar in pregnancy than average BMI women. You could equally well predict who would develop Type II just by looking at BMI.

-- Henci

Thank you for this very clear explanation.. it all makes sense to me.  I've had an uneasy feeling about the glucose tolerance test ever since I heard about it, and I wasn't sure why.  I think my uncle, an endocrinologist specializing in diabetes, told his daughter to forgo it during her pregnancy, but I'll have to ask him for details about that.

I have a weird feeling that my doctor is going to try to push me into all these tests because I have a strong family history of diabetes.  However, everyone in my family with diabetes developed it later in life (age 50 or older) and is/was obese (my mother, uncle, grandmother, grandmother's sisters).  I'm normal weight and very physically active, with a pretty healthy diet.  I don't know anyone with my profile who has type 2 diabetes, or who had to worry about GD.  I'm not worried, and I'd rather my doctor stop trying to make me worry.

To give a little background, Deebj wrote to Lamaze expressing her concern over what was said about gestational diabetes testing in the 2006 edition of Lamaze Pregnancy Magazine. Her e-mail was passed to me, and I asked her to post her e-mail on the Forum because I thought my response would be of general interest. I also asked if she could provide citations for the sources she cited so that I could evaluate them. Unfortunately, Deebj’s sources are textbooks, which means I don’t have access to them. Textbooks, though, present the conventional wisdom on any particular medical issue. Conventional wisdom is as Deebj states it, that is, that GDM is a serious condition with potentially severe adverse effects if left undiagnosed and untreated. The question is whether conventional wisdom is correct. The article Maria points Deebj to is mine; I wrote it a few years ago when I was employed as a resident expert on what was then iVillage’s ParentsPlace.com. In it, using the research evidence and pointing out the logical inconsistencies, I make the argument that the conventional wisdom is not correct. The article goes into much greater detail, but let me address the issues Deebj raises in her post.

·         GD diagnosis and treatment could not possibly prevent congenital malformations or miscarriage since these are 1^st trimester events and GD testing does not occur until the 3^rd trimester. Lost in the noise of the later studies is that, in any case, blood sugar metabolism is normal in the 1^st trimester. If it isn’t, it isn’t GD. As I wrote in my article, the hormones of pregnancy suppress the mother’s insulin, preventing her from metabolizing glucose in her own cells and making more circulating glucose available to the growing baby. GD is a matter of the woman’s pancreas not being able to keep up with demand, a problem that doesn’t arise until late in pregnancy.

·         A great deal of confusion arises by using the term “diabetes,” which mixes together pre-pregnant diabetes with what should properly be called “glucose (or carbohydrate) intolerance of pregnancy.” This terminology was used in Europe and is more accurate since with GDM, sugar levels do not reach the diagnostic threshold of true diabetes. The research physicians who have built their careers on gestational diabetes—this disease was invented in the 1970s and 1980s and did not exist before that time—chose the term deliberately at one of the early international workshops so that everyone would take the problem seriously, especially insurance companies, who would be expected to pay for all of this. The result is that two fundamentally different conditions are lumped together, and some complications, such as kidney problems, which only result from long-standing severe aberrations of glucose metabolism, are attributed to GD.

·         Some complications attributed to GD are because hyperglycemia is much more common in high-weight women. High-weight women are more likely to have high-weight babies—in fact, the baby’s birth weight is much more strongly correlated with the mother’s prepregnant weight than it is with her blood sugar level. Big babies are more likely to experience hypoglycemia after delivery and shoulder dystocia. High-weight women are also more likely to have hypertension or other health problems and therefore the consequent adverse effects of those medical conditions on the baby, including increased risk of death. Identifying and treating GD won’t make those problems go away, and they can be diagnosed and treated without reference to the mother’s blood sugar status.

·         Excess cesarean surgery rates, fetal distress, preterm birth, difficulty feeding could well be caused by the obstetric management that follows the diagnosis of GD. Among untreated gestational diabetic women, 20-30% will have a baby above the 90% range in birth weight instead of the statistically expected 10%, but the belief that most GD women are destined to have a large baby or that going to term poses risks leads to early term inductions and scheduled cesareans and to a too quick diagnosis of "failure to progress." Babies delivered before they are ready are more likely to have respiratory and breastfeeding difficulties. Cesarean sections interfere with establishing breastfeeding. Continuous, ongoing stress is strongly associated with preterm delivery, and the regimens of tests and procedures and the anxiety generated by the “diabetic” label is nothing if not stressful. Calorie-restricted diets and insulin to tolerance, which some protocols call for, can cause episodes of low blood sugar. Etc., etc.

·         Neonatal hypoglycemia is associated with high-weight babies, stressful deliveries, and preterm delivery. You don’t need to know that the mother is diabetic to identify babies at risk for hypoglycemia or to treat babies with symptomatic hypoglycemia.

·         Finally, pretty much everywhere women are routinely tested and treated for GD. If DeebJ is still seeing the problems she is seeing anyway, it’s because testing and treatment aren’t working.

I would be all for testing and treatment if all that happened was that women identified as having glucose intolerance of pregnancy were given good nutritional counseling and encouraged to exercise regularly and told these things, while important for every pregnant woman, were especially important for them. The GD diet—whole grains, fruits and veggies, avoid simple carbs, moderate in fat—is a good diet for any pregnant woman. Regular exercise is also beneficial. The possibility of identifying the rare case (about 1 in 1000) of a woman who has real diabetes would also be valuable. But that’s not what happens. The GD label means that the woman and her baby are subjected to a regimen of tests and medical interventions with considerable potential for harm and no convincing evidence of effectiveness. I’m with the authors of Guide to Effective Care in Pregnancy and Childbirth who classified GD testing and dietary and insulin treatment under “Forms of care unlikely to be beneficial.”

-- Henci