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Gestational Diabetes


Up to 9.2 percent of pregnant women in the United States have gestational diabetes, a form of glucose intolerance that can affect the health of both mother and baby. Not only is gestational diabetes common, it has been on the rise in the past 20 years. 

The diagnosis may sound frightening to an expectant mother but, when caught early, this problem can be managed effectively without causing any lasting health problems. At Yale Medicine, our specialists in Maternal-Fetal Medicine spend a great deal of time counseling patients on how to stay healthy, starting immediately from their first prenatal visit after diagnosis. 

"In addition, we have wonderful resources—a registered nurse and certified diabetic nurse educator—who also meet with the patients and serve as their main point of contact throughout the pregnancy," says Yale Medicine's Michelle Silasi, MD, a Yale Medicine Ob/Gyn. 

What is gestational diabetes?

Gestational diabetes mellitus occurs only in women during pregnancy. Although the exact cause is unknown, the prevailing theory is that the placenta—the organ that delivers water and nutrients to the fetus—produces hormones that block the mother’s ability to use insulin effectively. Insulin is a hormone that the body needs to convert glucose, or sugar, into energy that the body’s cells can use.

As the pregnancy continues, the placenta grows and produces more and more of these hormones; the end result is that glucose builds up in the blood, rather than being used by the mother's and fetus' cells.

Who is at risk for gestational diabetes?

Factors include:

·       Women who have had gestational diabetes in the past

·       Women who are obese

·       Women with a family history of diabetes or pre-diabetes

"About 90 percent of pregnant women have at least one risk factor for diabetes, but some risks are higher than others," Dr. Silasi says. 

Who should be tested for gestational diabetes?

In the U.S., every woman is tested for gestational diabetes, because only 10 percent of patients do not have a risk factor for diabetes.

Testing is usually done between weeks 24 and 28 using an oral glucose tolerance test. The pregnant woman drinks 75 grams of a sugary solution and then blood samples are drawn to monitor glucose levels about two hours later.

For pregnant women who are in a high-risk group, testing should be done as early as possible, often in the first trimester.

How is gestational diabetes treated?

The main goal of treatment is to keep the fetus from growing too large, which can harm both the mother and the baby. Patients will need to make changes in how they eat, and learn to monitor their own blood sugar levels. In some cases, a patient may need to self-administer insulin injections or take oral medication.

A change in diet often helps the most. A diet plan is working out with your medical team and may mean decreasing your calorie intake by as much as 20 to 30 percent.

Recommendations may also include:

  • Avoiding high-sugar snacks and desserts, including soda, punch, candy, chips, cookies, cakes and full-fat ice cream
  • Eating at least five servings a day of fruits and vegetables
  • Choosing whole grains: whole-wheat bread, brown rice and whole-wheat pasta
  • Switching to fat-free or low-fat dairy products
  • Eating only small amounts of red meat

Gestational diabetes usually goes away after delivery, and having it doesn’t mean you or your baby will definitely develop diabetes later in life.

At Yale Medicine, we provide counseling on healthy diet and exercise during pregnancy. "The basic take-home message is eat a healthy diet and be active during pregnancy," Dr. Silasi says. "Limiting simple sugars is key."

What are the risks for mothers and babies?

Mothers with gestational diabetes are at a higher risk for preeclampsia (hypertension during pregnancy), problems with labor and cesarean delivery. A large baby (considered more than 9 pounds at delivery) may cause injury to the mother during a vaginal delivery. A very large baby may suffer broken bones or nerve damage during delivery. It may be necessary to deliver the baby via caesarean section.

The child is also at a heightened risk of developing diabetes, obesity and metabolism problems later in life. Likewise, a mother who has had gestational diabetes is also at greater risk of developing type 2 diabetes later in life.

What are the risks for labor and delivery?

If a patient can keep her blood sugar levels close to normal and has no other complications, the best time to deliver is at 39 or 40 weeks.

High blood glucose during labor can cause complications for the baby, including chemical imbalances. But one of the main concerns is hypoglycemia, or low blood sugar in the baby immediately after delivery. This occurs if the mother's blood sugar levels have been high, which spikes the level of insulin in the fetus’ circulation.

After delivery, the baby still has a high insulin level, but without the high sugar level from the mother. This causes the newborn’s blood sugar level to become too low, and glucose may need to be administered intravenously. 

To avoid this, blood glucose is monitored very closely during labor. Insulin may be given to keep the mother's blood sugar in a normal range to prevent the baby's blood sugar from dropping excessively after delivery.

For most women, blood glucose levels return to normal after delivery. However, it is important for patients to take the glucose test again about six weeks postpartum. This is to ensure there is no sustained type 2 diabetes.

What makes Yale Medicine's approach to treating gestational diabetes stand out?

Committed to a deep understanding of the causes and treatment of diabetes, researchers affiliated with the Yale Medicine Diabetes Center and the Yale Diabetes Research Center conduct a wide variety of studies.

From the first successful studies of insulin pump technology in the 1970s to current investigations directed at understanding the cellular mechanisms underlying type 2 diabetes and the immunologic basis of type 1 diabetes, Yale Medicine has long been at the forefront of diabetes research and has been committed to providing our patient the finest treatment options available.