Gestational Diabetes

By Eileen B. Wyner, NP
Bulfinch Medical GroupEileen W

Let’s talk about pregnancy. Now, don’t leave me, WordPress didn’t get its wires crossed and bring you to Mommies 101. Diabetes is more familiar to us when we talk about Type 1 or Type 2, but there is another form of Diabetes that is particular to pregnant women only.

Gestational Diabetes (GDM) is Diabetes that occurs in pregnant women without a past history of Type 1 or Type 2.  It’s most commonly diagnosed between weeks 24-28 and disappears when the baby is born. GDM occurs in roughly 2-10% of pregnancies, but with the recent revised criteria from the American Diabetes Association (ADA), the incidence may be as high as 18%.

GDM occurs when pregnant women begin to develop insulin resistance (IR) during the second and third trimester. The same hormones released by the placenta to assist in fetal development are the same ones responsible for this IR. The mother’s pancreas works very hard to make enough insulin, but it doesn’t lower her glucose levels. The extra glucose in the mother’s blood crosses the placenta but insulin doesn’t, so the developing baby’s blood sugar becomes elevated.  The baby’s pancreas releases more insulin in response, which acts as a growth hormone and contributes to an increase in the baby’s birth weight.

Risk factors for developing GDM include: being overweight or obese at conception, being over age 35, positive family history of Diabetes, personal history of GDM with prior pregnancy, and being of African American, Hispanic, Native American or Asian ethnicity.


GDM is diagnosed with an oral glucose tolerance test, usually done around week 24 (though it may be done earlier for reasons of increased thirst, frequent urinary tract infections, or if sugar is found in the urine during monthly tests). The test starts with a fasting blood sugar, and then the mother is given a concentrated glucose drink.  Blood sugar is then checked at one hour and two hour intervals. According to the ADA guidelines, fasting range should be less than 92 mg/dL, the one hour range should be less than 180 mg/dL, and the two hour should be less than 153 mg/dL. GDM is diagnosed if just one test is elevated.

After diagnosis, it’s important to manage GDM as closely as possible–there are potential complications to both mother and baby which close monitoring can identify so the best treatment can be started as soon as possible. Women with GDM are at a greater risk for high blood pressure and preeclampsia.  The most common complication for the baby is increased birth weight (greater than 9 pounds) which may mean delivery via c-section will be required (though many vaginal deliveries occur as well).  Larger birth weight babies may face damage to their shoulders during birth—another reason a C-section may be needed.  Some babies may be born with hypoglycemia due to the extra insulin made by their pancreas, but this is very easily treated with sugar water or formula at birth and commonly corrects itself in 24 hours or less.  However, it is important to realize that many of these babies are born without any complications.

Managing GDM requires a close collaboration between mother and care team (obstetrician, diabetes educator, registered dietician, and endocrinologist). Diet modification and exercise are the most important aspects of Diabetes self management; it’s also important to check your blood sugar before meals and at bedtime. Many providers will also recommend women check their urine ketones each morning as a quick and easy way to see if the baby is receiving enough nutrition through the night. Occasional urinary ketones do not signal a problem but persistent elevations need to be reviewed with your care team.

There are times when lifestyle changes are not enough to keep blood sugar levels at goal. Human insulin is the gold standard for medical management and is one of the safest drugs to use in pregnancy. There is not definitive information on the safety in using oral agents or long acting insulin in pregnancy at this point, although there may be special circumstances where these medications are in use.

After Delivery

The great thing about gestational Diabetes is that it goes away as soon as the baby is born. However, because GDM is a risk factor for developing Type 2 Diabetes later in life, there are still several measures to take to ensure continued good health.  It’s important to monitor blood sugar values after delivery–approximately 1/3 to 2/3 of women who develop GDM with one pregnancy will have GDM with later pregnancies.  A glucose tolerance test 6 weeks after delivery needs to be done to be sure the mother hasn’t developed pre-diabetes or Type 2 (your primary care provider or obstetrician can set this up for you). If the results of this test are normal, the current recommendation is to obtain a fasting blood sugar every 3 years to screen for Type 2 Diabetes.   

The same lifestyle behaviors you adopted during pregnancy should be continued after delivery.  Stay active, follow a good diet, and try to keep your weight in a normal range to help prevent developing Type 2 Diabetes.  Remember, if you have any questions about your Diabetes management plan, you can always contact your health care provider.

Be well.