Normal Blood Sugars in Pregnancy

I have until now avoided discussing the issue of what normal blood sugars should be in pregnancy because it looked like gynecologists were being more aggressive with blood sugar control during pregnancy then other doctors.

Blood sugar control is particularly important in pregnancy because a fetus that is exposed to continually high blood sugars will experience significant changes in the way that its genes express which will affect its blood sugar metabolism for the rest of its life.

High blood sugar will also make babies very large, which poses problems when it is time for delivery, some life-threatening.

Blood sugars are lower in pregnant women because there is a higher blood volume during pregnancy, but it is starting to look like the targets gynecologists have been recommending, which would have been excellent for non-diabetic women are considerably higher than normal.

This was made clear by a new meta-study that analyzed a series of studies of the blood sugars of a wide range of normal pregnant women using Continuous Glucose Monitoring, home testing, and hospital lab results. It makes it clear that the current targets for pregnancy are probably too high.

Here is the full text version of the meta-study:

Patterns of Glycemia in Normal Pregnancy: Should the current therapeutic targets be challenged? Teri L. Hernandez, et al. Diabetes Care July 2011 vol. 34 no. 7 1660-1668.

It concludes that the following appear to be truly normal blood sugars for pregnant women:

AVERAGE BLOOD SUGARS IN NORMAL PREGNANT WOMEN
Fasting: 70.9 ± 7.8 mg/dl (3.94 mmol/L ± .43)
One Hour Post Meal: 108.9 ± 12.9 mg/dl (6.05 ± .72 mmol/L)
Two Hours Post Meal: 99.3 ±10.2 mg/dl (5.52 ± .57 mmol/L )

A commentary published in this month's Diabetes Care gives more insight into the importance of this study and why doctors should aggressively lower blood sugars in pregnancy. You can read it HERE. The Full text version is free.

The commentary suggests that pregnant women should strive for blood sugars that don't exceed the first standard deviation of normal (that's the average with the number following the "±" added to it. Doing that gives us targets that should not exceed

RECOMMENDED MAXIMUM BLOOD SUGARS FOR PREGNANT WOMEN WITH DIABETES
Fasting: 79 mg/dl (4.4 mmol/L)
One Hour After Meals: 122 mg/dl (6.8 mmol/L)
Two Hours After Meals: 110 m/gdl (6.1 mmol/L)

The challenge during pregnancy, of course, is to lower blood sugar without going too low because hypos can also cause problems for the fetus. In addition, the solution that works so well for non-pregnant people--cutting way back on carbs--raises issues.

Very low carb diets raise the concentration of ketones in the blood. This isn't a problem when we aren't pregnant--most of our organs can run quite happily burning ketones. But because ketones are usually produced when humans are starving, it is very possible that fetuses produced when the mother is in a ketogenic state may end up with environmentally-produced permanent changes to their genes (epigenetic changes, to use a technical term) that will predispose them to gaining weight once they are born, because ketones may signal the forming baby that they are being born into an environment of scarcity.

The fact that ketogenic diets downregulate T3 and slow the thyroid in non-pregnant people raises the question about whether a ketogenic diet might also have a negative effect on the baby's developing thyroid.

So it's generally considered to be best for pregnant women to lower their blood sugar as much as possible by cutting back on carbohydrates but to keep their carbs over the threshold (anywhere from 60-100 grams a day) where glycogen is depleted and the concentration of ketones in the blood and urine rises.

You can usually detect your own ketogenic threshold easily: it is the carbohydrate intake level at which, after eating at that level for three days, you suddenly lose anywhere from 3 to 8 lbs (depending on your size.) Raising carbs will immediately restore those quickly lost pounds because they are not fat (or growing baby) but the glycogen stored in your liver and muscles which gets burned away when your carbohydrate level is too low to replenish it.

If you eat only enough carbohydrates to keep your glycogen replenished, you won't have to worry that ketones will give your fetus the message that it's being born into an environment where starvation is occurring and shift its genes into a state where they optimize fat storage.

If you can't lower your blood sugar during pregnancy with diet alone, insulin is a safe medication for pregnant women and most doctors provide pregnant women with diabetes much better education in how to use insulin than family doctors do to their non-pregnant peers.

If you are reading this because you are pregnant and have just discovered you have gestational diabetes though you were not diabetic before your pregnancy, here's one last important fact to keep in mind: abnormal blood sugars in pregnancy almost always point to the pre-existence of abnormal sugars in the non-pregnant state that were missed by your doctor because the tests doctors use to screen for diabetes do a woefully bad job of diagnosing it until you have suffered years of high blood sugars that may irreversibly damage your organs.

Once you deliver your baby, don't rely on doctors to tell you if your blood sugar is normal. Test your blood sugar after meals every so often with a meter to make sure that you are not going over the 140 mg/dl (7.7 mmol/L) level at one hour that is truly normal in the non-pregnant state and that you are under 120 mg/dl (ideally far under) at two hours. If you are going over these levels, cut back on your carbohydrates and if that doesn't help, find a doctor willing to work with you to use safe drugs like metformin that can keep your sugars in the normal range for life.

Don't rely on the A1c test, as most doctors now do. It has been shown to be a poor guide to the high post-meal sugars that characterize the very early stages of Type 2 diabetes and which cause heart disease and early diabetic complications.