Gestational Diabetes
Gestational diabetes mellitus (or diabetes of pregnancy) is caused by a problem processing the glucose (or blood sugar) in your bloodstream. Glucose is important to the body — it provides fuel for cellular growth and metabolism. To be processed effectively, glucose requires a companion hormone known as insulin. Insulin facilitates the transfer of glucose into the cells where it is metabolized (or processed for energy).
If there is not enough insulin or if there is insulin that the body isn't using effectively, the result is a backup of glucose into the bloodstream, a situation that is potentially damaging to all of your organ systems and to a developing fetus.
When you develop gestational diabetes, your pancreas is still making plenty of insulin but your body isn't processing it efficiently. The condition, known as insulin resistance, is caused by certain placental hormones that counteract the effect of insulin (for example, estrogen, cortisol, and human placental lactogen, or HPL).
In most women, the condition doesn't reach critical levels, and their blood sugar levels stay within normal ranges. In others, excess blood glucose accumulates to potentially dangerous levels and treatment is required.
The Odds
Gestational diabetes mellitus (GDM) occurs in up to 7 percent of all pregnancies in the United States. Factors that may make you more likely to develop GDM include obesity (or high BMI), polyhydramnios (having excess amniotic fluid), a family history of diabetes, a diagnosis of GDM or large birth weight babies in previous pregnancies, and being over age 25.
Diagnosis and Treatment
Diagnosis of GDM is made with the oral glucose tolerance test (OGTT). (See Chapter 5 for details on how the OGTT is performed.)
Because blood sugar levels are influenced by dietary intake, your provider will probably try to treat your GDM with lifestyle and nutritional changes at the onset. A visit with a certified diabetes educator (CDE) and a registered dietitian (RD) can be invaluable in learning more about healthy menu planning, exercise, and the basics of blood sugar control.
You will have to self-test your blood glucose levels on a regular basis with a home meter. The home meter uses a lancet to prick your finger, arm, or another test site for a blood sample. The blood droplet is placed on a test reagent strip that goes into the meter, and the meter provides a blood glucose reading.
Testing is generally recommended first thing in the morning (a fasting test) and after meals (postprandial) — usually at one hour and again at two hours after eating. Your doctor may recommend testing at additional times, such as after exercise, if he feels it is warranted. Refer to the table below to see what blood glucose levels the American Diabetes Association recommends for women with gestational diabetes.
Test |
Range |
Fasting plasma glucose |
<105 mg/dl (5.8 mmol/l) |
1 hour postprandial plasma glucose |
<155 mg/dl (8.6 mmol/l) |
2 hour postprandial plasma glucose |
<130 mg/dl (7.2 mmol/l) |
*Note: mg/dL is the U.S. unit of measure for blood glucose readings, and mmol/l is the international measurement. |
If you don't experience significant improvement with dietary changes and your glucose levels still exceed normal ranges, you may have to take insulin injections to keep your blood sugar under control. Injections are typically taken before meals to counteract their impact on glucose levels. Insulin does not cross the placenta and is not harmful to fetal development.
Possible Long-Term Health Effects
Without proper treatment, uncontrolled blood glucose levels can result in fetal death or in a condition known as fetal macrosomia (or a baby that is too large). Blood glucose crosses the placenta in high levels, and the fetus responds by producing more insulin to process the load. The extra glucose is ultimately stored as fat, and the baby potentially grows too large for vaginal birth.
Newborns of GDM moms may also suffer from hypoglycemia at birth (or low blood sugar) as they are suddenly disconnected from the maternal surge of glucose and their high insulin production causes their blood glucose levels to plummet. They may also have an imbalance of blood calcium and blood magnesium levels at birth. Because of these risks, a neonatologist may be on the scene during labor and delivery to treat any potential complications.
Women who develop gestational diabetes have an increased risk of a diagnosis of type 2 diabetes later in life and should receive regular screening for the disease. Their children are also at risk for both type 2 diabetes and obesity. Fortunately, clinical studies have also shown that lifestyle changes involving regular exercise and a healthy diet can be extremely effective in preventing the onset of type 2 diabetes.
