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By Victoria Slater
If you are pregnant, you may have heard that you can “eat for two.” However, overeating can put you at risk for potentially dangerous conditions like gestational diabetes mellitus (GDM), a form of high blood sugar that occurs during pregnancy.
According to Stephen Thung, MD, director of Obstetrical Services at Ohio State Wexner Medical Center, when a woman is pregnant, the pancreas – the organ that produces insulin and helps regulate blood sugar by getting it out of the blood stream – has to go into overdrive.
The placenta – the organ that connects the mother to the baby --produces hormones that help support the baby by making it easier to deliver nutrients to your baby.
These placental hormones can often make it harder for your body to use its own insulin, a normal physiologic change in pregnancy called insulin resistance. As you can imagine back in the past when fast food restaurants, bakeries and other advances in modern society were not available – food was not always easy to come by. These pregnancy changes would keep more glucose in the maternal blood stream which would assure fetal nutrition. In today’s world, with food wherever we turn, this adaption can backfire on us and our bodies can deliver excessive sugar to the babies. Just like adults, high sugar levels can make babies grow.
“Some women are able to compensate for this increasing insulin resistance simply by increasing pancreatic insulin production while pregnant – these women do not have GDM,” Dr. Thung explains. “However, some women are not able to compensate for these changes. When insulin production is insufficient, hyperglycemia, or high blood sugar, occurs.”
While GDM is common – affecting more than 200,000 women in the U.S. each year – it can cause significant medical issues for you and your baby, including high birth weight (any weight over 8 pounds, 13 ounces) and in some cases birth injuries.
Because of this, Dr. Thung says it is important for all pregnant women to educate themselves on the condition. Fortunately, correctly identifying and managing gestational diabetes can reduce the risks.
Risk factors for gestational diabetes
Typically GDM is asymptomatic, but there are certain factors that can put you at a higher risk of developing GDM:
*You were overweight before pregnancy.
Extra weight makes it harder for your body to use insulin
*You are gaining weight too quickly during your pregnancy
*You have a family history of type 2 diabetes
*You are over the age of 25
*You were diagnosed with GDM in a previous pregnancy
*You previously gave birth to a baby that weighed over nine pounds.
*You have polycystic ovary syndrome, which is commonly associated with an increased insulin resistance.
Testing for gestational diabetes
“The standard is to do a two-step screening process. The first test is called a glucose challenge test (GCT)—which is done between 24 and 28 weeks when insulin resistance has already begun to increase,” Dr. Thung says. If you fail this, you move to a diagnostic glucose tolerance test (GTT).
During both of these tests, you will be given a sweet liquid to drink. For the initial screening GCT, your blood will be drawn one hour later to evaluate how your body processes sugar. This can be done at any time of the day and you do not have to be on an empty stomach. If your glucose value is above the cut-off used by your provider (commonly between 135-140 mg/dL), the test is followed by the diagnostic and time consuming three-hour glucose tolerance test (GTT).
“The GTT is typically done in the morning after fasting all night,” Dr. Thung explains. “Four blood tests are performed. The first test is a fasting blood glucose. Once that is done, the glucose drink is given, and your blood glucose is tested at one-hour, two-hour and three-hour intervals.”
If your blood sugar levels are once again above the cut-offs, then you will be diagnosed with GDM. We have now determined that with a high sugar load, your body cannot seem to produce enough insulin fast enough to keep your blood glucose in normal ranges. Fortunately most women do eventually get back to normal glucose levels—just slower than women without GDM.
How is GDM treated?
If you are diagnosed with GDM, the first step is starting a diet and exercise regimen to manage weight gain, Dr. Thung says.
"Diet and regular exercise are the most important first step elements to managing GDM and avoiding the unwanted outcomes associated with GDM. You are not sick when you are pregnant and in most cases we absolutely want you active—at least 30 minutes of brisk walking a day and perhaps more if you are already active at baseline” he says.
If these lifestyle changes do not lower your blood glucose levels, you will likely need some form of medication to help bring your glucose levels back to normal. This can be achieved with oral pills such as metformin or glyburide or with multiple insulin injections every day until you give birth. Fortunately, only 10 to 20 percent of women with GDM will require more than diet and exercise.
Is gestational diabetes dangerous?
The greatest risk associated with GDM is actually not with the baby but with long term maternal health.
“Pregnancy is like a stress test and be a crystal ball into the future. We know that GDM mothers are at high risk for developing type 2 diabetes later in life,” says Dr. Thung.
About 50 percent women with GDM go on to develop diabetes in 10 years.
Routine screening – immediately after delivery and about every three years – can identify it early, and early treatment can prevent damaging side effects and conditions such as heart disease, blindness, renal failure or dialysis and early death.
According to Dr. Thung, pregnant women diagnosed with GDM also have an increased risk of giving birth to excessively large and heavy babies. Larger babies can present challenges for delivery. As such, cesarean delivery is more common for these women. Even when vaginal delivery is successful, babies delivered to diabetic mothers are more likely to have a complication known as shoulder dystocia. This is when the baby’s head is delivered, but the shoulders do not follow like they are supposed. Having a more difficult delivery complicated by shoulder dystocia places the baby at risk for birth injuries to the head, neck and arms.
Women with GDM also have an increased risk of preeclampsia—a condition associated with high blood pressure and leaking proteins in the urine. This is a common condition, and women who have ever been to a certified nurse midwife or physician know that they receive a blood pressure and are asked for a urine sample at almost every prenatal visit.
All that work is to identify preeclampsia early and to protect maternal health. Preeclampsia that is not properly cared for can escalate and cause a variety of maternal complications.
Can I pass GDM on to my baby?
If you are diagnosed with GDM, your baby may have blood sugar concerns, as well.
“As you can imagine, babies who are used to chronic hyperglycemia do not transition well after birth, can become hypoglycemic after delivery and may need to be admitted to our NICU for management to keep their blood sugar up,” Dr. Thung says. “We test all GDM babies for hypoglycemia after delivery.”
Good glycemic control can minimize these risks especially while in labor, Dr. Thung adds.
“GDM runs in families. Typically, we do not expect GDM mothers to have immediately diabetic babies – and that predisposition may be noted many decades later in adulthood,” he explains.
Does gestational diabetes go away after giving birth?
Once the baby and placenta are delivered, according to Dr. Thung, the hormones that caused the maternal insulin resistance resolve. This rapidly decreases the likelihood of continuing hyperglycemia.
“That being said, some women who have GDM are actually women with unknown overt diabetes that was never diagnosed before pregnancy,” Dr. Thung says.
In addition, women with a history of GDM are at a higher risk of developing it in future pregnancies.
“Having GDM in one pregnancy is one of the strongest risk factors for having GDM in a subsequent pregnancy,” Dr. Thung shares.