The Big Gestational Diabetes Post
Gestational diabetes testing is a very interesting subject! I have compiled a post with many different sections that should cover most of the information one would need in order to determine the appropriateness of gestational diabetes screening or testing for themselves as an individual.
Of course, the option to NOT test for this condition is always there! I always encourage anyone considering a screening or diagnostic test during pregnancy (or otherwise) to think about what they will gain and lose with the results.
What information are you hoping to get about yourself, from an outside source? How will having this information change the way you feel about yourself? About your baby?
Really take time to sit with all of this, and do research. Check in with your intuition and see what your body and your baby are telling you about this topic.
Once you are armed with information and tuned into your feelings and gut instincts, you can make the decision that is best for YOU.
A lot of the info in this post comes from Gail Hart’s book Research Updates for Midwives as well as Anne Frye’s Holistic Midwifery Vol 1 and her book Understanding Diagnostic Tests In The Childbearing Year. Other sources are linked within the text of this post. Highly recommend you get any or all of these books if you’re at all interested in pregnancy and birth on a deeper-than-normal level :)
Checking In With Yourself And Your Baby
There is a lot of rational and logical information and discussion around the topic of gestational diabetes and the testing used to determine your status of this condition.
But perhaps more important is the idea of checking in with yourself on a spiritual level, and checking in with your baby.
You can absorb all of the external information you want on this topic, but what it all will boil down to is how you FEEL about what you’ve learned and what your SPIRIT is guiding you to do in this situation.
I hope if you’re in a situation where you’re weighing the pros and cons of the gestational diabetes test (the glucose tolerance test or GTT) in pregnancy, that you take some time before AND after reading this post to sit in silence, check in with your soul, your spirit, your higher power if you believe in one, and your baby.
Ask yourself how you feel about this on a spiritual level. What knowledge do you hope to gain? How do you want to FEEL during this pregnancy, and how do you want your baby to FEEL about YOU and about them self and about THE OUTSIDE WORLD, when all of this is said and done?
The spiritual side of pregnancy should not be neglected, and even talking about gestational diabetes screening and testing should ultimately fall back to what your guiding inner voice has to say about it all.
Diabetes vs Gestational Diabetes
Diabetes mellitus (DM) is very different from gestational diabetes (GD)..
Things we know about diabetes:
Some people are unaware they have diabetes or they have a mild case of diabetes and only develop severe symptoms during pregnancy.
True diabetes is dangerous and carries serious risk to both mother and baby during pregnancy.
Gestational diabetes, on the other hand, is a transient condition that only appears during pregnancy and is based on arbitrary and constantly changing lab values.
Some people have viewed GD historically as a syndrome with no risks to mother or baby and with no symptoms other than an increased chance of growing a larger-than-average baby.
There have been studies that have come out though, that have said that ANY elevation of blood glucose levels during pregnancy leads to poor pregnancy outcomes.
A woman with diabetes mellitus – regardless of when it is first discovered – has blood glucose values far in excess of those used to diagnose “gestational diabetes.” She will usually have a history of insulin-dependent diabetes among family members, and show SIGNS AND SYMPTOMS of diabetes:
excessive weight loss or weight gain
extreme thirst
polyuria (increased frequency, and larger amounts, of urine)
Glycosuria (sugar in the urine)
ketonuria (ketones in the urine)
Possibly cardiovascular symptoms – leading to high blood pressure
In pregnancy, those with true diabetes will show:
the fundal heights will usually be large-for-dates
the baby will be large-for-dates
excessive amniotic fluid (hydramnios) is common
True diabetes is characterized by high blood glucose levels secondary to (or because of) insufficient insulin secretion or insufficient insulin action, or both.
Chronic high blood sugar levels occur because the cells cannot use the glucose and the tissues begin to starve because the body metabolizes protein and fat to try to make up for what it perceives as LOW blood sugar levels.
Diabetes is associated with dysfunction, damage, and eventual failure of organs, especially the heart, eyes, kidneys, nerves, and blood vessels. There are different types of diabetes.
Women who have previously been diagnosed with diabetes before becoming pregnant do not have GD, but rather diabetes and pregnancy.
Insulin dependent diabetic mothers can have extremely complicated pregnancies. There are inherent risks from diabetes but also risks imposed by improper medical management of diabetes during pregnancy.
In pregnancy the diabetic has a risk of having an exceptionally large baby -- fed from her exceptionally high blood sugar levels – who doesn’t handle swings and drops in those levels – and who is at risk for intrauterine fetal death, stillbirth, damage from an obstructed labor, and for hypoglycemia after birth.
The woman with diabetes will fail blood sugar lab tests. Her fasting levels will be high. Her post-prandials (post-meal blood glucose levels) will be high. Her GTTs (glucose tolerance tests) will be, without question, HIGH! Her symptoms show she is a diabetic and the blood tests will confirm it.
But what about “gestational diabetes?” Is it – in and of itself – a high-risk condition? NO!
Gestational diabetes is a term to describe decreased glucose tolerance during pregnancy.
The creation of the idea of gestational diabetes is controversial because the research used to create this “condition” many years ago was based on oral glucose tolerance tests with no dietary histories taken into account AND study populations included women with previous poor pregnancy outcomes or risk factors in their current pregnancy as well as women known to be diabetics.. And compared their outcomes with the general population.
The initial studies used to frame what gestational diabetes was, defined GD as a woman who had high glucose levels during pregnancy AND developed true diabetes later in their life.
Researchers at that time were searching for a reason for a general trend of larger than had been normal babies… this was around the same time that women were being encouraged to NOT diet and restrict calories during pregnancy, so naturally babies in the 1970s were being born larger than babies in the 1950s. But researchers viewed this as a problem.
A healthy baby who is slightly larger than has been the average is a very different ordeal than a very large and very unhealthy baby that is born to a woman with true diabetes.
Historically, women labeled as gestational diabetics were subjected to interventions such as starvation diets, preterm induction of labor, and withholding of nourishment from their newborns, which of course contributed to poorer outcomes among these women and their babies.
An initial Cochrane review found no correlation between GD and poor pregnancy and birth outcomes was evident when GTT results were considered separately from these numerous other risk factors of starvation diets, preterm induction, etc..
A woman diagnosed with GD solely by a failed GTT does not fit the diagnostic criteria which would label her diabetic if she were not pregnant.
In other words, if the only reason she is called “gestational diabetic” is because of a failed GTT, then she will have no signs or symptoms of diabetes and she has no risk of harm from diabetes.
And neither does her baby. Her baby has NO increased risk of IUFD (intrauterine fetal demise) – or of stillbirth in labor.
The woman DOES have an increased risk of having a larger baby – thirty percent of women with GD will have a baby over 9 pounds. (But notice that means that 70% will deliver normal sized babies.)
Most of this risk could be predicted based on the same categories which were used to label her “high risk for GD” – high body weight, multiparity (having had many pregnancies), older age, and certain ethnic groups. Thirty percent of those women have larger babies. The glucose tolerance test tells us nothing new!
This risk of a large baby occurs WITHOUT treatment of any kind, and if we treat women labeled as gestational diabetic with diet or insulin we do NOT lower the risk of a large baby in any way.
The rate of large babies is statistically the same even when a woman follows a “gestational diabetes diet” which restricts calories and carbohydrates.
Dietary therapy as treatment for GD does not reduce birth weight or alter cesarean rates. Studies of women who followed a diabetic diet and also took insulin, do show an average reduction in fetal size of about a quarter of a pound – but this is an amount which is not obstetrically significant, and does not affect the rate of cesarean section.
The baby of a GD mother has only two risks – and these risks are common to all large babies – regardless of whether or not mom passed a GTT: Larger babies have a higher risk of cesarean, of forceps delivery, and of long labor or obstructed labor. They have a higher risk of shoulder dystocia (which itself is not a major risk for asphyxia, but only for temporary brachial plexus injury). Like other large babies, they can suffer low blood sugar if feeding is withheld after birth (the prevention for hypoglycemia is FEEDING THE BABY (breast milk, not sugar water).
Does gestational diabetes in and of itself – actually exist as a “disease process?” A process which can harm mothers or babies? No.
What Are The Risks Of Gestational Diabetes?
Women with the label GD have a very high risk of elective cesarean section, of induction of labor to “avoid macrosomia”, of unnecessary cesarean and augmentation in labor because of the fear of the baby not fitting through the pelvis, and of mishandling of the birth itself because of the fear of shoulder dystocia.
The Cochrane Data Base, which questions the entire definition of gestational diabetes (using “quotation marks” around the words in their material), and which strongly condemns “treatment’ based on sloppy and insufficient data, categorize GD under “treatments with no evidence of effectiveness, which may cause harm.”
“All forms of glucose tolerance testing should be reviewed. Women in whom overt diabetes is suspected should be followed with fasting or blood glucose estimations two hours after meals throughout pregnancy. The available data provide no evidence to support the wide recommendation that all pregnant women should be screened for “gestational diabetes,” let alone that they should be treated with insulin. Until the risks of minor elevations of glucose during pregnancy have been established in appropriately conducted trials, therapy based on this diagnosis must be critically reviewed. The use of injectable therapy (insulin) on the basis of the available data is highly contentious, and in many other fields of medical practice such aggressive therapy without proven benefit would be considered unethical.”
Women in certain blood sugar ranges do have an increased risk of developing diabetes later in life, but there is no risk to the baby. The baby may be 8lbs 13oz or larger, but race, age, parity, and maternal weight have far more impact on that factor (fetal weight) than “gestational diabetes” status.
How We Process Carbohydrates - Normally And During Pregnancy
How do we normally process carbohydrates? The breakdown of carbohydrates results in the formation of glucose, a simple sugar that is the primary food for the cells. Pancreatic beta-cells produce a hormone called insulin, which regulates the use of glucose in the body. Insulin functions as the key that allows glucose to enter the cells. Once glucose enters the cells, it combines with oxygen to form carbon dioxide and water. The energy released in this process is used for muscular work, maintaining body temperature, and nourishing nerve tissues, particularly the brain.
Once ingested, carbohydrates are quickly converted to glucose, causing blood glucose levels to rise. In a healthy woman whose pancreas is functioning well, the pancreas starts to release insulin almost instantly. This enables glucose to enter muscle and fat cells. Insulin also helps the liver store excess glucose as glycogen, while decreasing the breakdown of glycogen that has been previously stored. Glucose and insulin levels usually peak within 30 to 60 minutes after a meal, and return to baseline after three to four hours.
After blood glucose levels are back to baseline, to keep them from dipping too low, the liver releases glycogen, which is converted to glucose to provide nourishment to the body until more food can be eaten. If glycogen stores become too low (8-12 hours of no eating or more), and the body still needs glucose, proteins and fats are broken down to meet this need, providing the liver with glycerol to convert to glucose, as well as free fatty acids, which get converted to ketones (which is why we see ketones in the urine when women have not been eating enough calories during pregnancy).
Women process sugar differently when they are pregnant.. in order to enhance nutrient delivery to the baby, our body exhibits a very different way of metabolizing carbohydrates, fats, proteins, and ketones.
The placenta produces hormones (lactogen, estrogen, and progesterone) which COUNTERACT the function of insulin!
The placenta also makes strong enzymes that destroy insulin.
Additional shifts in maternal hormones help suppress insulin, as does maternal weight gain because it increases the percentage of body fat.
As pregnancy advances, insulin resistance and insensitivity rises to a level almost seen in people with Type 2 diabetes!
The pregnant mother’s pancreas also secretes more insulin during pregnancy (2.5-3 times more than non-pregnant by the end of pregnancy) to compensate for this. The suppression of insulin allows more glucose to remain available in the mother’s bloodstream for longer periods of time.
Glucose-sparing (the mother’s body not utilizing glucose for energy and instead using proteins and fats (which, remember, are metabolized with ketones as a by-product (which could contribute to ketones showing in urine at the end of pregnancy))) increases as pregnancy advances, peaking during the third trimester when the baby gains the most weight and needs the most nourishment to grow.
Fetal blood glucose levels are usually 20-40 mg/dl lower than that of the mother, showing us that the placenta likely plays a role in regulating glucose delivery to the baby as well.
The swings between high and low blood sugar are larger and normal blood sugar levels are a bit higher during pregnancy.. This is one of the reasons morning sickness occurs, because the body needs glucose levels to be higher than a woman is used to keeping them, so it’s easier for a woman to have low blood sugar than before she was pregnant, especially in the morning when she hasn’t eaten for 8-12 hours or so.
So, in spite of this knowledge, gestational diabetes testing during pregnancy uses “normal ranges” to determine gestational diabetes status that are lower than non-pregnant normal blood sugar levels!
Whoever came up with this idea rejected the idea that higher levels are physiological during pregnancy and that it’s necessary for fetal and placental growth to have that extra glucose floating around in the blood.
The confusion - I think - lies in the idea that high elevations in blood sugar in ACTUAL diabetes (DM) are dangerous for the baby (which is true), that normal elevations in blood sugar levels during pregnancy can lead to larger-than-average babies (which is true), but the confusing part is “they” are assuming worse pregnancy outcomes BECAUSE of larger than normal babies, which hasn’t been shown to be true.
So the thing they’re worried about is not applicable, really.
And blood sugar levels during pregnancy should definitely NOT be lower than they are while NOT pregnant, which is how they’ve set up these “normal ranges” for the glucose tolerance test.
Different Groups/Organizations Use Different Normal Ranges For Determining Gestational Diabetes Status During Pregnancy
These are the numbers used by different groups and different doctors (I will show recommendations for non-pregnant people as well as pregnant people, so you can see that the recommendations for pregnant women are sometimes LOWER than non-pregnant!):
The American Diabetes Association testing recommendations for non-pregnant people is the 75 gram two hour screen, with normal values set at:
fasting <115
1 hour < 200
2 hours < 140.
The World Health Organization's new recommendation for screening non-pregnant people is 75 g two-hour GTT, with normal values set at:
fasting <126
2 hours < 140
WHO believes this is more reliable than other screens with a lower risk of “false positives”.
Pregnant women are more commonly (and arbitrarily) given the 100g 3 hour challenge test, with varying “normal” results listed by different groups (some use these same numbers for a 50g test, which makes no sense since it uses half as much sugar).
National Diabetes Data Group original scale for pregnant women:
Fasting <105 (see how it is so much LOWER than the scale used for non-pregnant people?)
1 hour < 190
2 hours < 165
3 hours < 145
The Carpenter and Coustan scale for pregnant women suggests a 100gm glucose test with women having to exceed levels in TWO time frames for diagnosis of GD:
Fasting < 95 (even lower than the other scales for non-pregnant people!!)
1 hour < 180
2 hours < 155
3 hours < 140.
The American Diabetes Association screen for pregnancy is a one hour 50g glucose SCREEN (non-fasting) with one hour of <140 as the normal scale. If the woman fails the screen (aka she has levels higher than 140 after an hour) she will take the 3 hour GTT (with 75g glucose solution) on a separate day using the Carpenter and Coustan scale. Officially, TWO values must be met or exceeded to qualify as GD, however, GD is often diagnosed when only one value is too high.
However, because blood sugars normally run higher in pregnancy – even in non-diabetic women -- about 15% of women will “fail” the 50g screen and become candidates for the 3-hour GTT.
The International Association of Diabetes and Pregnancy Study Group (IADPSG) is now using the HAPO recommendations (HAPO is the group/study that said that ANY elevation of blood glucose levels during pregnancy leads to poor outcomes) for a 75 gram test with the following normal ranges:
Fasting <92
1 hour <180
or
the One Step Test --- blood is drawn only once after the 75g dose and must follow the following normal range:
2 hour < 153
This is what the American College of Obstetricians and Gynecologists (ACOG) recommends/says:
“All pregnant women should be screened for GD, whether by patient history, clinical risk factors, or a 50g, 1-hour loading test to determine blood glucose levels.”
This is the ADA screen mentioned above. Keep in mind that they said “or,” meaning not EVERY woman should have to be screened with the 50g 1 hour test.
BUT, according to ACOG, GD can only be diagnosed based on the result of the 100g, 3-hour oral glucose tolerance test, using either the Carpenter and Coustan scale or the National Diabetes Data Group scale. “A positive diagnosis requires that two or more thresholds be met or exceeded”
“Diagnosis of GD based on the one-step screening and diagnosis test outlined in the International Association of Diabetes in Pregnancy Study Group guidelines is not recommended at this time because there is no evidence that diagnosis using these criteria leads to clinically significant improvements in maternal or newborn outcomes.”
It's estimated that using the IADPSG and HAPO recommendations will result in over 17% of pregnant women being diagnosed with Gestational Diabetes!
Who Should Be Tested For Gestational Diabetes (And Who Shouldn’t)
According to ACOG - women who fit all the low risk categories do not “need” to be screened:
under 25 years of age,
not “morbidly obese”
no family history
not a high risk ethnic group
Women who “should be screened” are women who:
have had previous complicated deliveries because of a big baby
have previously had babies over 9lbs
have been labelled as obese
or have close relatives with diabetes
Some issues with this criteria: weight gain is emphasized over adequate dietary choices.
Also, any woman who has had a large baby -- even healthy women with healthy large babies -- is considered “at risk of developing GD.”
Many women who are very healthy and well-nourished would be categorized as high risk when they are actually quite low risk for ACTUALLY developing GD.
Another issue is that a woman who has had a poor pregnancy outcome previously BECAUSE of poor nutrition and whose glucose levels fall in the GD range can wind up being labeled GD in this pregnancy and put on a restricted diet, which will raise her risk of having more problems in THIS pregnancy from inadequate nutrition.
If you are a woman who has had previous poor pregnancy outcomes or previously large babies, we should always be asking: what was your diet like? What other symptoms did you experience during that pregnancy?
What Lifestyle Or Dietary Changes Might Affect Gestational Diabetes Status or Test Results?
The timing of the test is important. The most accurate time for screening is between 24 to 28 weeks.
Giving iron to women who are not iron deficient can increase the risk of GD. Women with artificially high iron levels are at increased risk of developing GD.
Women on iron supplements had higher blood pressure, higher fasting blood sugar, and higher levels on the glucose tolerance test. They had 2 to 3x the risk of developing GD and hypertension than pregnant women who weren’t taking iron. Iron supplementation is associated with glucose impairment in midpregnancy.
Because antioxidants influence glucose tolerance, vitamin C intake may affect the development of gestational diabetes.
Researchers in Seattle conducted a prospective cohort study of over 700 women, testing their plasma vitamin C levels at various points in pregnancy.
“Women with plasma ascorbic acid <55.9 micromol/L (lowest quartile) experienced a 3.1-fold increased risk of gestational diabetes (95% CI = 1.0 - 9.7) compared with women whose concentrations were > or = 74.6 micromol/L (upper quartile). Women who consumed <70 mg vitamin C daily experienced a 1.8-fold increased risk of gestational diabetes compared with women who consumed higher amounts.”
Is this an effect of dietary intake? Did the women with higher levels eat more fruits and vegetables and thus lower their risk? Or could this be due to a protective effect from vitamin C alone? And if so, could vitamin C supplements lower the incidence of GD?
We don’t have that answer yet, but it seems another good reason to encourage women to consume at least the RDA of vitamin C.
Limiting refined sugars and other refined carbohydrate intake can reduce a woman’s risk of being labeled GD as well as developing true diabetes later in life.
Other factors that can alter results of the GTT:
infection
lack of exercise
poor diet
smoking
caffeine intake
fear and anxiety.
Some people have abnormal results if tested in the morning but when retested in the afternoon are normal.
Hyperthyroidism slows intestinal absorption that can cause GTT results to be abnormally low. Endocrine hormone levels should be determined before GTT.
What Should Blood Sugar Levels Be For A Healthy Person?
Normal non-pregnant fasting levels are 99mg/dl or lower, two hour postprandial (post-meal) values are 139 or lower.
Normally, blood glucose levels rise between 20 and 50 mg/dl over baseline one to two hours after a person begins to eat.
Fasting pregnancy blood glucose levels should be less than 120. So two hour postprandial numbers would be 140-170 mg/dl based on the normal non-pregnant glucose physiology, perhaps even higher with normal pregnancy variations in physiology.
If A Woman Has Been Diagnosed With GD, What Advice Can We Give Her?
Diets don’t have a significant impact on fetal weight – at best a few ounces, not enough to change chances of cesarean for macrosomia (large baby).
We know there are risks to restricted calorie diets, and to low-carbohydrate diets in pregnancy, but moderating her carbohydrate intake makes good sense.
A healthy diet will keep both mother and baby healthy. Follow a whole food diet, remove processed foods and simple carbohydrates.
The risk of cesarean has much more to do with protocols and fetal position than with the size of the baby!
And remember that the majority (70%) of women labeled as GD will have normal-sized babies – even if they make no changes at all in their diets.
It would be best to assess women based on their own unique health and bodies. Right now there is no "official" way to distinguish between the woman who MASSIVELY FAILS a GTT, compared to a woman who barely fails.
The woman with consistently high blood sugar levels is at risk, but it is illogical to think that the woman with "barely elevated" levels suffers the same risk. She might have no risk at all.
Women who have been diagnosed with GD should know their test results and how “off” their results were compared to normal parameters.
You can get an at-home glucometer to check glucose levels, and regular exercise to burn extra glucose can help.
Adding Jerusalem artichokes, cucumbers, and liver to the diet can help as well as supplementing with B6 and chromium.
Check the Brewer Diet website for their diabetes nutrition during pregnancy info.
Why The Traditional Glucose Screening or GTT May Not Be A Good Idea
The standard screening test is a 50g glucose drink consumed by the pregnant woman with blood sugar tested after a certain amount of time has elapsed.
For this screening test, often there is no forewarning and no preparation or consideration given to what the woman has eaten that day (or not).
If that test result is positive or has glucose levels too high (generally over 140mg/dl), a 3 hour glucose tolerance test is ordered, which not only requires fasting (which is not advised in pregnancy), but is notoriously inaccurate and different scales are used in different offices/practices to determine whether a woman has “passed” or “failed” (see above section on the different scales used).
Giving a woman who doesn’t normally eat refined sugar a concentrated bolus of refined sugar before testing can skew results by causing a physiological reaction to the glucose overload which can mimic diabetes by showing elevated blood glucose levels.
When the pancreas is inundated with an unusually high glucose load, insulin is not produced fast enough to compensate and her blood sugar levels will remain abnormally high for an extended period of time as the body tries to catch up.
Eventually the pancreas catches up and overcompensates by sending out a surge of insulin which brings the blood glucose level down sharply and can actually cause hypoglycemia, or too much glucose removed from the blood (low blood sugar).
The timeframe for this whole process varies, but a 1 to 3 hour GTT may not be long enough to show the delayed rebound effect on the test results.
What Type of Screening Can We Do That Is NOT the GTT In Order To Try To Determine Glucose Metabolism?
We can order a fasting blood glucose lab test at the beginning of pregnancy.
This can be a good early indication of a glucose regulation problem before most of the other influences of pregnancy come into play during later pregnancy.
If a woman falls into the high risk category or for some reason wants further testing, or if she shows glucose and ketones or glucose alone in her urine, we can order a fasting blood glucose lab, as well as hemoglobin A1C.
If these results are concerning, we can do a fasting and post-meal blood glucose test with an at-home glucometer.
Together, these tests and their values will give us a good idea of her overall glucose regulation, even if she’s still early in her first trimester.
And depending on these test results, we may want to order thyroid hormone tests as well because abnormal thyroid function can affect glucose regulation.
If the test results show values within the prediabetic range, we can look at diet again and switch things up to eat better, avoid refined carbs, and exercise regularly, which is what we do for every pregnant woman anyway!
We can then retest at or after 6 weeks postpartum to see if glucose levels have fallen below prediabetic values. If they’re not lower, that would be an indication that she has been prediabetic or diabetic since before pregnancy and did NOT “just” have GD.
Postprandial (post-meal) glucose testing is the best physiologic screening we can do.
We assess glucose levels after a normal meal by using an at-home glucometer. In pregnant women, the one hour post-meal value (start the clock when the first bite is consumed), is typically the highest and normally higher than non-pregnant numbers (so, normally higher than 140, depending on the contents of the meal), and usually take more than two to three hours to fall back to pre-meal levels.
This will tell us the most about how the woman’s body responds to real foods.
Proper Preparation For Blood Glucose Testing:
Eliminate all refined carbs and processed foods and eat extremely well (high fiber carbs/whole foods), for at least a week before the test.
Carbo-load with healthy carbs for three days before the blood draw (over 150g daily of whole grains, beans, and vegetable starches like potatoes, squash, etc).
The last meal before the fast begins should contain at least 50g of complex carbs.
Stop vitamin C supplementation for three days prior to testing (high levels of vit C can cause false negative results).
Drink plenty of water during the overnight fasting period before the test (and for the previous days) so blood isn’t concentrated.
Exercise moderately for the three days prior.
How The Glucose Tolerance Test Works
These tests come in one, two, three, and four hour oral glucose tolerance tests. A concentrated liquid glucose drink is ingested which contains 50 (usually only used in the glucose tolerance SCREEN) or 75 or 100g of glucose, and must be ingested within 5 minutes. The timer for the first post-glucose blood draw begins when you start to drink the solution.
These tests often cause nausea because with a normal meal, the body breaks down foods that contain numerous other nutrients and soluble fiber slows the absorption of glucose.
When pure glucose is taken, none of these processes are in play and the pancreas must deal with this assault of simple sugar all at once.
These tests often have a lack of reproducibility, meaning 70% of those who do test positive have normal results when retested.
Different types of blood products are used in testing glucose levels and it’s important to understand how the blood product tested can affect results.
Whole blood, blood serum, or blood plasma may be used, and you should know which type of blood product (made from your blood) was tested when comparing your test results to the reference ranges. You should also know which blood product was used to derive the reference range used by the office. They should match.
Whole venous blood, if used, must be either frozen or tested immediately to be accurate. Whole blood is seldom used because of its unreliability and how quickly it deteriorates at room temperature. Also, the glucose levels in whole blood depend upon the hematocrit, so accurate results can only be obtained when the reference range is adjusted according to the individual’s hematocrit. This variable is not an issue when only plasma (described below) is used.
Capillary whole blood is obtained by pricking the finger, and values are affected by the chemical reagents and equipment used. Capillary values are drastically different than whole blood values, and for example, one hour after the ingestion of 100g of glucose, capillary whole blood values may be 30 to 40 mg/ml higher than venous whole blood values!
Serum can also be used. Serum is the fluid portion of blood minus the blood cells, and values are about the same for both plasma (discussed below) and serum, but only if the blood is centrifuged immediately, refrigerated, and tested within two to four hours. If red cells are not removed immediately, plasma and serum values may differ considerably.
Venous plasma is the liquid portion of the blood that still contains the clotting factors. The glucose concentration of venous plasma is more stable than that of serum or whole blood, and because of that it has become the standard specimen for glucose testing. Plasma glucose, however, is unstable to an extent. To minimize deterioration, unpreserved specimens should be centrifuged immediately and tested. If this is impossible, blood should be drawn into a grey-top tube preserved with sodium fluoride and then refrigerated. Specimens should be tested within two to four hours to minimize altered glucose levels. An interesting aspect of plasma is that as pregnancy continues, plasma volume increases and after about 28 weeks, it has increased by about 50% over pre-pregnancy levels. These variations will affect how the glucose content of whole blood registers on testing, but have not been taken into account by any of the reference ranges used for pregnancy. For this reason, venous plasma values are most comparable to the existing reference ranges, regardless of pregnancy status.
Alternatives To The Standard GTT
Because of how unpleasant the standard GTT is, alternative strategies have been studied and proposed.
Two separate studies used jelly beans, one study used 18 jelly beans and one study used 28 jelly beans. Jelly beans, although just as sweet as glucose drinks, are solid so have a somewhat slower uptake than liquid pure glucose.
There has also been a “breakfast tolerance test” (BTT) developed, where the woman would eat a standard 600 calorie mixed nutrient breakfast and blood is checked after one hour. Average one hour result plus two standard deviations for the BTT was blood level of 120 mg/dl. This test had a 75% sensitivity and 94% specificity.
Some offices/midwives use juices that have the equivalent amount of carbohydrates as the pure glucose drink (like orange juice), but the nutrients in juice are more complex and will break down and absorb differently than pure glucose solution.
GTTs are designed to maximize pancreatic stress by giving the purest sugar possible, so it will flood the system and challenge the pancreas to release a maximum amount of insulin. If you are really interested in showing your body’s reaction to this challenge and determining if you are diabetic, it’s best to do the actual glucose solution drink.
If you’re not wanting to determine your true diabetes status but for some reason can’t NOT take the test, ask your provider if you can choose a different method, with juice or jelly beans, or to paint an even truer picture of how your body processes sugars, the BTT!
GD And The Baby
When the mother has truly elevated blood glucose levels during pregnancy, the baby becomes accustomed to her high levels and after birth, the baby is at risk for low blood sugar levels.
If uncorrected, this could lead to tremors, respiratory distress, listlessness, abnormal crying, feeding difficulties, possibly convulsions and brain damage if severe.
This can also occur during pregnancy if the mother is diagnosed with GD and then put on a very restricted calorie diet and the baby is under-supplied with glucose in utero.
To prevent this after the birth, early and frequent nursing is important. The baby might constantly nurse for many hours after birth to try to get their blood sugar levels evened out.
The baby and mother must not be separated at any point after birth so that the baby can nurse freely.
Some doctors recommend 12 hours of NICU time for observation and hourly heel sticks to determine blood glucose levels in the baby after birth. This is not ideal.
Conclusion
I hope you now have plenty to think about and as much information as you need in order to make a concrete decision for yourself during this pregnancy with regards to GD screening and testing. You should know the alternatives, risks, benefits, and about how you’d feel with the option of doing nothing and not testing for this condition.
And as I said in the beginning, this is only one type of information. The other type is that of your soul and your gut feelings and intuition. Check in on all levels and see what feels right for you!
Only YOU can make this decision for yourself.
Please let me know if you have any further questions or would like clarification on any of this!
