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What causes gestational diabetes?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Changing hormones and weight gain are part of a healthy pregnancy. But both changes make it hard for your body to keep up with its need for a hormone called insulin. When that happens, your body doesn't get the energy it needs from the food you eat. And excess of glucose in blood results in gestational diabetes.

This answer is based on source information from the National Institute of Diabetes and Digestive and Kidney Diseases.

Gestational diabetes is the result of hormonal changes that occur during pregnancy. These hormonal changes decrease the body's ability to use sugar from foods that we eat, specifically carbohydrates. When the body is unable to use all of the sugar from food, the mother's blood glucose levels can increase. High blood glucose levels can increase the risk of the mother developing high blood pressure; they can also result in a large fetus, making delivery difficult.

Women who are at risk for developing gestational diabetes are those who may be overweight before becoming pregnant, have a family history of diabetes, are over the age of 25, have previously given birth to a large (over nine pounds) baby or have had gestational diabetes in a previous pregnancy.

Dr. Jeanne Morrison, PhD
Family Practitioner

Gestational diabetes mellitus (GDM) is a state of carbohydrate intolerance during pregnancy. The exact cause is difficult to pinpoint but GDM may result from:

  • Unidentified preexisting diabetes mellitus
  • Unmasking a metabolic abnormality caused by the added stress of pregnancy
  • Alteration of maternal metabolism cause by the fluctuations in hormones during pregnancy
  • Development of insulin resistance in response to the presence of the anti-insulin action of placenta hormones

There are several different types of diabetes. In all types, the body can't efficiently produce or use insulin, a hormone that allows cells to turn glucose (sugar) into usable fuel.

When you're pregnant, pregnancy hormones make it harder for insulin to move glucose from your blood into the cells. This is called insulin resistance. If your body can't produce enough insulin to overcome the effects of insulin resistance, you'll develop gestational diabetes.

We don't know what causes gestational diabetes, but we have some clues. The placenta supports the baby as it grows. Hormones from the placenta help the baby develop. But these hormones also block the action of the mother's insulin in her body. This problem is called insulin resistance. Insulin resistance makes it hard for the mother's body to use insulin. She may need up to three times as much insulin.

Gestational diabetes starts when your body is not able to make and use all the insulin it needs for pregnancy. Without enough insulin, glucose cannot leave the blood and be changed to energy. Glucose builds up in the blood to high levels. This is called hyperglycemia.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.