Causes of Gestational Diabetes: Learn the Causes & Risks of Developing Gestational Diabetes

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Gestational diabetes mellitus, or just gestational diabetes (GD), is a serious illness that can affect pregnant women. Left untreated, it can cause serious health problems in the fetus. Fortunately, GD screenings are conducted routinely on pregnant women, and the disease is highly treatable once diagnosed.

What is Gestational Diabetes?

Gestational diabetes is uncontrollable high blood sugar occurring in a pregnant woman who has never suffered diabetes outside of pregnancy. It affects about 4% of pregnant women. Though less well known than type I and type II diabetes, it is a third form of diabetes mellitus and the only one that can be cured relatively easily. Delivery of the placenta cures GD.


During digestion, food, especially carbohydrate-rich food, breaks down into the simple sugar glucose. Two hormones control the level of glucose in the blood: glucagon (which increases blood glucose) and insulin (which decreases it).

During pregnancy, the placenta secretes hormones to sustain the pregnancy. Even in a normal pregnancy, researchers believe these hormones affect the mother’s body’s ability to respond to insulin, a phenomenon called insulin resistance. Insulin resistance in pregnancy may be an adaptation to allow the fetus to obtain an adequate supply of energy in the form of glucose. A pregnant woman normally produces more insulin to compensate for insulin resistance.

Although the cause of GD is not well understood, researchers believe that it involves insulin resistance that is greater than normal, resulting in uncontrollably high blood glucose. Insulin resistance also occurs in type II diabetes. Both type II diabetes and GD are metabolic disorders. GD is not related to type I diabetes, which is an autoimmune disease caused by the destruction of insulin-producing cells in the pancreas by the immune system.

Because the insulin resistance is ultimately caused by the placenta, GD does not develop early in pregnancy while the placenta is small. It appears around the second trimester and tends to worsen until the end of the pregnancy as the placenta grows.

Risk Factors

Certain women are at a higher risk for developing gestational diabetes than others. Risk factors include the following:

  • Family history of type II diabetes or gestational diabetes
  • Prediabetes, previous pregnancy with gestational diabetes, or previous delivery of a baby over nine pounds
  • Obesity
  • Maternal age over 25
  • African, Asian, Hispanic, or Native American ethnicity
  • Polycystic ovarian syndrome
  • Smoking

Continue to Part 2 of the series on gestational diabetes for information on symptoms, screening and diagnosis, and adverse effects on the fetus.