Gestational Diabetes

What is gestational diabetes?

Gestational diabetes is a type of diabetes that happens during pregnancy. Unlike type 1 diabetes, gestational diabetes is not caused by having too little insulin. Instead a hormone made by your placenta keeps your body from using the insulin as it should. This is called insulin resistance. Blood sugar (glucose) then builds up in your blood instead of being absorbed by the cells in your body.

The symptoms of gestational diabetes usually go away after delivery. But sometimes they do not, or you may have a greater risk of developing type 2 diabetes later.

What causes gestational diabetes?

Healthcare providers do not know what causes gestational diabetes, but they do know what happens.

The placenta gives your growing baby nutrients and water. The placenta also makes several hormones to keep the pregnancy healthy. These hormones include:

  • Estrogen
  • Progesterone
  • Cortisol
  • Human placental lactogen

These hormones can affect how your body uses insulin (contra-insulin effect). This usually begins about 20 to 24 weeks into your pregnancy and could lead to gestational diabetes.

During pregnancy, more fat is stored in your body, you take in more calories, and you may get less exercise. All of these things can make your blood sugar (glucose) levels higher than normal and possibly lead to gestational diabetes.

As the placenta grows, it makes more of the hormones. The risk for insulin resistance becomes greater. Normally your pancreas is able to make more insulin to overcome insulin resistance. But if it cannot make enough to overcome the effects of the placenta’s hormones, you can develop gestational diabetes.

Who is at risk for gestational diabetes?

Any woman can develop gestational diabetes during pregnancy. But you may be more likely to get it if you:

  • Are overweight or obese
  • Have a family history of diabetes
  • Are older than 25
  • Are African American, American Indian, Asian American, Hispanic or Latino, or Pacific Islander
  • Have prediabetes (impaired glucose tolerance)
  • Have high blood pressure

What are the symptoms of gestational diabetes?

Gestational diabetes does not cause any symptoms. That’s why it’s important to get tested for it if you are at high risk.

If your blood sugar levels are very high, you may have these symptoms:

  • You urinate more than normal
  • You are hungrier or thirstier than normal.
  • You have blurred vision
  • You have nausea and vomiting
  • You lose weight even though you are hungrier

How is gestational diabetes diagnosed?

You should be tested for gestational diabetes in your 24th to 28th week of pregnancy.

The American Diabetes Association also recommends that you be tested for type 2 diabetes if you have risk factors for this condition. This testing should be done at your first prenatal visit.

Screening is done by the following tests.

One-step method

This method uses a 75-gram oral glucose tolerance test. Your fasting blood sugar (glucose) level is measured after an overnight fast of at least 8 hours. Then you drink a special beverage high in sugar. Your healthcare provider measures your blood sugar again at 1 and 2 hours after taking the beverage. If your levels are higher than any one of the following blood sugar levels, you have gestational diabetes.

  • Fasting: 92 mg/dL or higher
  • 1 hour: 180 mg/dL or higher
  • 2 hour: 153 mg/dL or higher

Two-step method

Step 1. This method uses a 50-gram glucose tolerance test with a blood sugar level check at 1 hour. If your blood sugar at 1 hour is 130 to 140 mg/dL or higher, you go to step 2.  

Step 2. A 100-gram glucose tolerance test is done while you are fasting. Gestational diabetes is diagnosed when you have at least 2 of the following blood sugar levels:

  • Fasting: 105 mg/dL or higher
  • 1 hour: 190 mg/dL or higher
  • 2 hour: 165 mg/dL or higher
  • 3 hour: 145 mg/dL or higher

If you are diagnosed with gestational diabetes, you should get tested for diabetes 4 to 12 weeks after your baby is born. You should also get this screening at least every three years for the rest of your life.