Gestational diabetes mellitus (GDM) is a type of diabetes, or insulin resistance, that develops around the middle of pregnancy and ends after delivery. Women who are pregnant, have high blood sugar (glucose) levels and have never had diabetes before are said to have GDM. Gestational diabetes occurs when the body isn't able to properly use insulin or to make enough insulin to keep blood sugar levels in normal ranges, causing higher-than-normal levels. Without enough insulin, or with the body not using it properly, glucose cannot leave the blood and be used for energy. GDM usually develops around the sixth month of pregnancy, or between the twenty-fourth and twenty-eighth weeks.
It can be unhealthy for both mother and baby if blood sugar levels are too high. Because GDM does not appear until later in the pregnancy when the baby has been formed, it does not cause birth defects seen in some babies whose mother had diabetes before pregnancy. If GDM is not treated properly or controlled, it can cause problems for the baby that include low blood sugar levels, jaundice, breathing problems, and high insulin levels. In addition, it can cause a baby to weigh more than normal at birth, which can make delivery more difficult and possibly necessitate a cesarean section. Babies born with excess insulin run a higher risk of obesity in childhood and adulthood, thereby putting them at higher risk for Type 2 diabetes later in life. GDM is different from other forms of diabetes in that it only occurs during pregnancy and goes away after delivery. Women who have diabetes before becoming pregnant are not classified as having gestational diabetes.
Gestational diabetes mellitus (GDM) affects between 3 and 5 percent of all pregnant women, about 135,000 each year. Women who have gestational diabetes during pregnancy are more susceptible to Type 2 diabetes later in life, though basic lifestyle changes may help lower this risk. Once a woman develops GDM in a pregnancy, the chances are 2 in 3 that she will develop GDM in future pregnancies.
Some women do not experience any symptoms with gestational diabetes. Therefore, it is standard practice to screen most pregnant women at the twenty-eighth week of pregnancy. Women who are high risk for GDM are screened at their first doctor's visit as well as at twenty-eight weeks. The most common test used to screen for GDM is the 50-gram glucose challenge test. This nonfasting test measures the body's ability to use, or metabolize, glucose, the sugar that the body uses for energy. The test involves drinking a sweet, sugary beverage that contains a standard amount of glucose. A blood glucose test is taken one hour after the drink is consumed. Normal blood glucose values at the one-hour mark should be less than 140 mg/dl (milligrams per deciliter). If the blood glucose levels come out higher than normal, the results are considered abnormal and indicate the need for further testing.
Abnormal results after the one-hour screening do not necessarily mean a diagnosis of gestational diabetes. Instead, the next step is a three-hour oral glucose tolerance test (OGTT). This test involves fasting overnight (for about 12 hours) and is usually done first thing in the morning. The woman drinks a sweet, sugary beverage with a high concentration of glucose (100 grams). Her blood glucose levels are tested before drinking the beverage, which is a fasting blood glucose. After drinking the beverage, blood glucose is drawn every hour for three hours. If at least two of the blood glucose levels show up abnormal, a diagnosis of GDM is made. Early detection is important so that blood sugar levels can be controlled and complications for the mother and infant can help be prevented.
Gestational diabetes seems to stem from the placenta and its production of several hormones that help the baby develop during pregnancy. During the second and third trimesters, these “insulin-antagonist” hormone levels increase and can cause insulin resistance. Insulin resistance makes it difficult for the mother's body to properly utilize insulin, the hormone that manages glucose or blood sugar levels. This causes a higher-than-normal blood sugar level, or hyperglycemia. After delivery, these hormone levels, as well as glucose levels, return to normal.
Some women are at higher risk than others for developing gestational diabetes. Among this group are women with a strong family history of diabetes or a first-degree relative with diabetes, women who are obese, women who have had problem pregnancies in the past, women with a history of having babies more than 9 pounds at birth, women who have had gestational diabetes in past pregnancies, and women over the age of twenty-five. Also counted as high risk are women of certain ethnicities, including African-Americans, Latinos, Asian-Americans, Native Americans, and Pacific Islanders.
Signs and Symptoms
Gestational diabetes can be tricky because symptoms are not always obvious, and some of the symptoms may appear as normal symptoms of pregnancy. This makes screening for all women very important. Symptoms will vary from woman to woman, as each is an individual situation. Most of the symptoms that do appear are due to high blood sugar levels or hyperglycemia.
The most common signs and symptoms include the following:
Less common signs and symptoms can also include:
Frequent infections, including bladder, vagina, and skin
Women who develop GDM during pregnancy are also at greater risk for problems such as high blood pressure and preeclampsia.
If you are diagnosed with gestational diabetes, treatment needs to begin immediately. The goal of treatment is to help keep blood sugar levels within a safe range to help reduce the risk of complications to you and your baby during pregnancy and after delivery. Most women are able to keep their blood sugar levels within a safe range by eating a well-balanced diet that balances carbohydrates (55 to 60 percent of calories), protein, and fat. Regular exercise can also help to keep blood sugar levels in balance. Treatment should also include daily blood glucose testing. If a balanced diet and regular exercise are not enough to help control blood sugar levels, insulin injections may be needed. Oral glucose medications are not recommended during pregnancy.
Women with gestational diabetes should do the following:
Eat smaller, more frequent meals throughout the day and not skip meals.
Eat the required amount of calories and include all of the food groups each day.
Eat a lower-carbohydrate breakfast because insulin resistance is the greatest when you first wake up.
Eat a consistent amount of carbohydrates at each meal and snack.
Add lean protein to each meal such as lean meat, egg whites, tuna, legumes, or nonfat dairy products.
Choose foods higher in fiber, such as whole grains, legumes, fruit, and raw vegetables.
Consume most carbohydrates from whole foods such as fruits, vegetables, legumes, and whole grains as opposed to sugary foods. Carbohydrates should not be overly restricted but should be moderate and spread throughout the day.
Minimize intake of foods concentrated with sugar and saturated fats (animal fats). This doesn't mean you have to cut out all sugar, but you should moderate your intake.
Drink at least 64 ounces of water daily.
Be sure you are getting enough of all the essential vitamins and minerals each day.
Exercise regularly in a way that does not cause fetal distress, uterine contraction, or maternal hypertension. Check with your health-care provider for instruction on safe exercise.
Keep a steady and healthy weight gain.
There is no single way to treat all women with gestational diabetes. It is important that women work with their physician and a registered dietitian to help them develop an individualized treatment plan. If you develop GDM, it is important to keep in mind that you can still deliver a healthy baby. With the correct treatment and management of your blood sugar through lifestyle changes, you can have a perfectly normal pregnancy. It is important for you to be monitored on a regular basis by your doctor.