Robert Wood Johnson University Hospital
 

Gestational Diabetes

Gestational Diabetes Mellitus (GDM)

What is GDM?

Gestational diabetes mellitus is a condition in which the glucose level is elevated and other diabetic symptoms appear during pregnancy in a woman who has not previously been diagnosed with diabetes. All diabetic symptoms disappear following delivery.

Unlike type 1 diabetes, gestational diabetes is not caused by a lack of insulin, but by other hormones produced during pregnancy that can make insulin less effective, a condition referred to as insulin resistance.

Approximately 3 to 8 percent of all pregnant women in the United States are diagnosed with gestational diabetes.

What causes GDM?

Although the cause of GDM is not known, there are some theories as to why the condition occurs.

The placenta supplies a growing fetus with nutrients and water, and also produces a variety of hormones to maintain the pregnancy. Some of these hormones (estrogen, cortisol, and human placental lactogen) can have a blocking effect on insulin. This is called contra-insulin effect, which usually begins about 20 to 24 weeks into the pregnancy.

As the placenta grows, more of these hormones are produced, and the risk of insulin resistance becomes greater. Normally, the pancreas is able to make additional insulin to overcome insulin resistance, but when the production of insulin is not enough to overcome the effect of the placental hormones, gestational diabetes results.

What is a risk factor?

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.

Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors.

But, knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

What are the risks factors associated with GDM?

Although any woman can develop GDM during pregnancy, some of the factors that may increase the risk include the following:

Although increased glucose in the urine is often included in the list of risk factors, it is not believed to be a reliable indicator for GDM.

How is GDM diagnosed?

The American Diabetes Association recommends screening for undiagnosed type 2 diabetes at the first prenatal visit in women with diabetes risk factors. In pregnant women not known to have diabetes, GDM testing should be performed at 24 to 28 weeks of gestation.

In addition, women wit diagnosed GDM should be screened for persistent diabetes 6-12 weeks postpartum. It is also recommended that women with a history of GDM undergo lifelong screening for the development of diabetes or prediabetes at least every three years.

What is the treatment for GDM?

Specific treatment for gestational diabetes will be determined by your doctor based on:

Treatment for gestational diabetes focuses on keeping blood glucose levels in the normal range. Treatment may include:

Possible complications for the baby

Unlike type 1 diabetes, gestational diabetes generally does not cause birth defects. Birth defects usually originate sometime during the first trimester (before the 13th week) of pregnancy. The insulin resistance from the contra-insulin hormones produced by the placenta does not usually occur until approximately the 24th week. Women with gestational diabetes mellitus generally have normal blood sugar levels during the critical first trimester.

The complications of GDM are usually manageable and preventable. The key to prevention is careful control of blood sugar levels just as soon as the diagnosis is made.

Infants of mothers with gestational diabetes are vulnerable to several chemical imbalances, such as low serum calcium and low serum magnesium levels, but, in general, there are two major problems of gestational diabetes: macrosomia and hypoglycemia.

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