Should You do the Gestational Diabetes Test While Pregnant?
A question was posted in a mom group asking if there were any alternatives to the gestational diabetes test that produce the same results (aka. resulting in a diagnosis of gestational diabetes).
The short answer? No.
The long answer? Let’s dive in below and look at some research.
What is gestational diabetes?
Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications affecting 17 million pregnancies worldwide. In Canada, about 10% of pregnancies are complicated with gestational diabetes.
Why does gestational diabetes happen?
During early pregnancy, the body becomes more sensitive to insulin to store glucose for later use. As pregnancy progresses, hormones can make the body less sensitive to insulin, leading to gestational diabetes in some pregnant people. Those who produce enough insulin, can maintain normal blood sugar levels. While those who cannot may develop gestational diabetes after 20 weeks of pregnancy.
The American Diabetes Association recommends routine screening for gestational diabetes during pregnancy because many cases may actually be pre-existing hyperglycemia. After giving birth, a history of gestational diabetes increases the risk of developing type 2 diabetes, cardiovascular disease, and metabolic syndrome in the future.
What are the risk factors for gestational diabetes?
The main risk factors for gestational diabetes include:
Previous gestational diabetes diagnosis - strongest risk factor
Family history of type 2 diabetes - strongest risk factor
Overweight or obesity (BMI over 30)
Ethnicity (South and East Asians, Hispanic, Black, Native Americans, Aboriginal and Torres Strait Islanders, Middle Easterners)
Maternal age over 35 years
Physical inactivity before or in early pregnancy
Gestational weight gain
Past history of macrosomic baby (>4000g/8.8lbs at birth) or stillbirth
Depression before pregnancy
Factors associated with a lower risk of GDM include:
Age, younger than 25-30
White race
BMI of 25 or less
No family history of diabetes
No history of glucose intolerance or adverse pregnancy outcomes relating to GDM
Are there any complications associated with gestational diabetes?
Yes. There are both short and longterm complications of gestational diabetes for both the mother and baby. Potential complications of gestational diabetes include:
For the mother: preeclampsia, preterm labor, need for induction of labor and cesarean delivery. Most importantly:
There is a 8-10 fold higher risk of developing Type 2 Diabetes, highest 3-6 years after a GDM pregnancy.
There is a 2x higher risk of developing cardiovascular disease, within the first decade after birth.
For the baby: neonatal hypoglycemia, stillbirth, macrosomia and birth trauma, long-term risk of metabolic disease
How do you screen for gestational diabetes?
In Canada, universal screening for gestational diabetes is recommended between 24-28 weeks of pregnancy by the Society of Obstetricians and Gynecologists of Canada (SOGC). A two-step approach is used:
The first step is a 50g oral glucose challenge test (OCGT). The pregnant person should consume the drink within a 10 minute window and have their random glucose (blood sugar) tested 1 hour later.
Here are the important numbers for the OGCT:
If their glucose is less than 7.8mmol/L, no further testing is required - you don’t have GDM, yay!
If their glucose is greater than or equal to 7.8-11.0 mmol/L, a 75g oral glucose tolerance test will be recommended - you will repeat the test again, but with a higher amount of glucose
If their glucose is greater than or equal to 11.1 mmol/L, GDM is diagnosed without further testing
2. The second step is a 75g oral glucose tolerance test (OGTT). The pregnant person will have their fasting glucose measured, and then their random glucose measured 1 and 2 hours after drinking the 75g of glucose.
Here are the important numbers for the OGTT:
A fasting blood sugar is greater than or equal to 5.3 mmol/L - leading to a diagnosis of GDM
A random blood sugar is greater than or equal to 10.6 mmol/L, ONE hour after consuming the drink - leading to a diagnosis of GDM
A random blood sugar is greater than or equal to 9.0 mmol/L, TWO hours after consuming the drink - leading to a diagnosis of GDM
Are there alternative tests to screen for gestational diabetes?
To reiterate my above comment, no.
There is no alternative testing that is the gold standard for screening gestational diabetes. Let’s discuss some of the research.
HbA1c
This is a profile of how much sugar the red blood cells have over a 3 month period. While it’s a low cost test that requires no drink it may be useful in identifying those at higher risk for GDM complications preconception and in early pregnancy but should not be used alone in the assessment or management of GDM.
Fresh Test
This is advertised as the only additive-free glucose drink with only 3 ingredients being non-GMO, BPA free, GF, vegan. Sounds great, right? If you look at the research, only 10 people were assessed, and all of them (9 female, 1 male) were not pregnant. It seems like more research is needed tom determine if this is a comparable test to what is routinely offered.
Jelly Beans
There is a double crossover study with 160 pregnant women who ingested 28 jelly beans, compared with a 1 hour 50g OGCT. There were no significant differences between the jelly beans and glucose drink - which is good! But you still need to eat 28 (colourful!) jelly beans.
Candy Twists
A double crossover study of 20 pregnant women who ingested 47g of candy twists compared to the 1 hour 50g OGCT. No significant differences arose between the twists and drink - also good. But it’s seemingly a lot of candy to eat in a short period of time.
HOMA-IR
This is a measure of insulin resistance, and may help in identifying those at highest risk for GDM in preconception and early pregnancy. There is no evidence to use this in standard of care in pregnancy.
Continuous Glucose Monitoring (CGM)
Continuous glucose monitoring is recommended for those with pre-existing type 1 diabetes in addition to pre and postprandial glucose measures, but should not substitute blood glucose monitoring for glycemic control. According to the American Diabetes Association, the decision to use CGM in pregnant women with type 2 diabetes or GDM should be based on their individual circumstance, preferences, and needs.
Why is it important to follow standards of care?
Is drinking 50g of sugar in 10 minutes gross? Absolutely. There’s no doubt about it. But for the most part - you’re likely going to do it one time. Also, if you ever had a grande PSL - that contains 50g of sugar too.
As you saw above, there are incredible risks of not doing this test. Out of the major complications - preeclampsia, preterm labour, stillbirth (!!!). It doesn’t seem worth it to skip out on a test that you might fail. Especially if you meet any of the above risk factors.
For the most part, pregnancy is a time when you’ll have regular contact with a health care provider (maybe your Family Doctor, OB, or Midwife), and likely you haven’t had a barrage of blood tests done before (ex. if you’ve been seeking fertility treatments, you’ve likely done so. many. tests.). As I mentioned above, it’s thought that most cases of GDM are from pre-existing cases of high blood sugar.
Perhaps we can re-frame this “disgusting/not-natural” glucose drink as an opportunity to learn about our future risk of type 2 diabetes and cardiovascular disease, in the hopes that we can implement diet and lifestyle changes during pregnancy and the postpartum to prevent them.
Obviously this is a nuanced conversation and a singular blog post should not be the end of your research. Speak to your healthcare provider to discuss your risk of developing gestational diabetes, and what the outcomes may be if you don’t proceed with the test. Making an informed choice is important.