There is no known specific cause but it is believed the hormones of pregnancy reduce a woman's receptivity to insulin resulting in high blood sugar. Gestational diabetes affects an estimated two to three percent of pregnant women. Frequently women with gestational diabetes exhibit no symptoms. However, possible symptoms include increased thirst, increased urination, fatigue, nausea and vomiting, bladder and yeast infection, and blurred vision.
Risk factors for gestational diabetes include:
* a family history of type 2 (adult-onset) diabetes
* maternal age - a woman's risk factor increases the older she is
* ethnic background (those with higher risk factors include African-Americans, North American native peoples and Hispanics)
* obesity
* gestational diabetes in a previous pregnancy
* a previous pregnancy that resulted in a child with a birth weight of 9 pounds or more
* smoking doubles the risk of gestational diabetes
Generally a test for gestational diabetes is carried out between the 24th and 28th week of pregnancy.
Often, gestational diabetes can be managed through a combination of diet and exercise. If that is not possible, it is treated with insulin, in a similar manner to diabetes mellitus.
There are several tests intended to identify gestational diabetes in pregnant women. The first, called the Screening glucose challenge test, is a preliminary screening test performed between 26-28 weeks. If a woman tests positive during this screening test, the second test, called the Glucose Tolerance Test, may be performed. This test will diagnose whether diabetes exists or not by indicating whether or not the body is using glucose (a type of sugar) effectively. The Glucose Challenge Screening is now considered to be a standard test performed during the second trimester of pregnancy.
The glucose values used to detect gestational diabetes were first determined by O'Sullivan and Mahan (1964) in a retrospective study designed to detect risk of developing type II diabetes in the future. The values were set using whole blood and required two values reaching or exceeding the value to be positive. [2] Subsequent information has led to alteration in O'Sullivan's criteria. For example: when methods for blood glucose determination changed from the use of whole blood to venous plasma samples, the criteria for GDM were also changed once whole blood glucose values are lower than plasma levels due to glucose uptake by hemoglobin (NDDG,1979).
The diagnostic criteria from the National Diabetes Data Group (NDDG) have been used most often, but some centers rely on the Carpenter and Coustan criteria, which set the cutoff for normal at lower values. Compared with the NDDG criteria, the Carpenter and Coustan criteria lead to a diagnosis of gestational diabetes in 54 percent more pregnant women, with an increased cost and no compelling evidence of improved perinatal outcomes.
Women who are considered at risk for gestational diabetes are given a screening test called a 50 gram glucose challenge between the 24th and 28th weeks of pregnancy (those with two or more risk factors may be tested earlier). The glucose challenge is performed by giving 50 grams of a glucose drink and then drawing a blood sample one hour later and measuring the level of blood glucose present. Women with a blood sugar level greater than 140 mg/dl may have gestational diabetes, and require a follow up test called a 3-houroral glucose tolerance test (OGTT). [4]
The test should be done in the morning after an overnight fast of between 8 and 14 h and after at least 3 days of unrestricted diet (>=150 g carbohydrate per day) and unlimited physical activity. The subject should remain seated and should not smoke throughout the test. The American Diabetes Association sets the following guidelines for results from the OGTT (oral glucose tolerance test).
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.
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.[6]
For Mother
* Hypertension
* Preeclampsia
* Increased risk for developing type 2 diabetes
For Baby
* Macrosomia
* Hypoglycemia
* Jaundice
* Low calcium and magnesium
* Respiratory distress syndrome (RDS)
* Increased risk for childhood and adult obesity
* Increased risk of type 2 diabetes later in life
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