Approximately 10% 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, its incidence has increased over the past 20 years.

The diagnosis may sound frightening to an expectant mother, but when caught early, this issue can be managed effectively without causing lasting health problems.

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 result is that glucose builds up in the blood, rather than being used by the mother's and fetus's cells.

Factors include:

· Women who have had gestational diabetes in the past

· Women with obesity

· Women with a family history of diabetes or prediabetes

About 90% of pregnant women have at least one risk factor for diabetes, but some risks are higher than others.

In the U.S., every woman is tested for gestational diabetes.

Testing is usually done between weeks 24 and 28 of gestation 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 in a high-risk group, testing should be done as early as possible, often in the first trimester.

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 change how they eat and learn to monitor their 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. Recommendations may 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
• Eating 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.

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 Cesarean 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.

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 insulin level in the fetus’s 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.

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 patients the finest treatment options available.

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