Glucose Tolerance Test

Gestational diabetes usually begins in the fifth or sixth month of pregnancy (between the 24th and 28th weeks), and it often has no symptoms, so most women are routinely tested between the 24th and 28th weeks of pregnancy. However, if you are considered high-risk for gestational diabetes, you will be screened before the 24th week of pregnancy.

The gestational diabetes screening test, also called the one hour glucose test, consists of drinking a sweet liquid called Glucola, and then having your blood analyzed about one hour later. A blood sugar level below 140 milligrams per deciliter (mg/dL) is usually considered normal. If your blood sugar level is higher than this, you do not necessarily have gestational diabetes, it simply means you need more extensive testing, called the glucose tolerance test (GTT), to diagnose or rule out gestational diabetes. This test requires you to fast for 8 hours (or overnight), have a baseline blood test and then drink another sweet liquid (with a higher glucose content) and have your blood re-tested every hour for three hours. If at least two of the blood sugar readings are higher than normal, you are considered to have gestational diabetes. If only one of the tests shows an elevated blood sugar level, you may be asked to repeat the GTT in two to four weeks.

Women who are considered high risk for gestational diabetes include those who had preexisting diabetes, were diagnosed and treated for gestational diabetes during a previous pregnancy, or those who may have had large babies with previous pregnancies. Other women who are considered high-risk include those who:

• Are obese
• Who have had other problems in pregnancy such as previous miscarriages or preeclampsia
• Are older (the tendency to develop diabetes increases with age)
• Who were large babies when they were born (nine pounds or more)
• Who have a history of diabetes in their family
• Who have recurrent or persistent bladder infections or vaginal yeast infections

Most women who develop gestational diabetes are able to manage it with a modified diet and regular exercise (always check with your doctor before beginning any exercise regimen). The most effective way to manage your diet is to have your doctor or midwife refer you to a registered dietician who can create a diet plan for you. He or she will determine how many calories you and your baby need on a daily basis; as well as the correct balance of protein, fats, and carbohydrates; and teach you how to distribute them throughout the day to maintain your energy and blood glucose levels. Depending on how serious your condition is, you may have to test your blood several times a day to monitor your blood sugar levels as well. If you are not able to control your blood sugar by diet and exercise, you will have to give yourself daily insulin shots.

To control elevated blood sugar:

• Eat a variety of foods, distributing the calories and carbohydrates evenly throughout the day.

• Don't skip meals! Even if you're feeling bloated or nauseas, eat something. This will help maintain an even your blood sugar level throughout the day.

• Your body uses high-fiber foods more slowly than carbohydrates and will keep your blood sugar levels from spiking too high after meals. High-fiber foods include whole grain breads and pastas, cereals, dried peas, and beans.

After birth, a baby born to a mother with gestational diabetes may have breathing problems, low blood sugar, an increased risk for jaundice, polycythemia (extra red blood cells in the body), and hypocalcemia (low calcium in the blood), as well as a higher risk of developing childhood and adult obesity and diabetes. In extreme cases, the baby’s heart function could be affected.

Unlike other types of diabetes, gestational diabetes usually resolves itself after delivery; however, you will have to take a glucose test about six to 12 weeks after delivery to be sure your blood sugar levels have returned to normal. A small percentage of women remain diabetic after delivery, but many experts believe these women had undiagnosed cases of diabetes before they became pregnant.

According to the American Diabetes Association, gestational diabetes is the most common pregnancy complication, affecting between 2 and 5 percent of women. It can strike women who were diabetic before becoming pregnant, as well as those who have no history of diabetes, and occurs more frequently in African-Americans, Hispanic/Latino Americans, Pacific Islanders, South or East Asians and Native Americans than in other groups.

Gestational diabetes is characterized by high blood sugar. When you eat food, your digestive system breaks down the food into glucose, a type of sugar, which enters your bloodstream and is converted to energy with the help of insulin, a hormone secreted by your pancreas. Just like type 1 and type 2 diabetes, gestational diabetes occurs when the glucose remains in the bloodstream instead of being converted to energy. Experts at the American Diabetes Association are not sure why this occurs, but they believe that hormones secreted during pregnancy may make it hard for the mother’s body to use insulin (a condition called insulin resistance), which allows more glucose to stay in the bloodstream.

If diabetes is left untreated, it can damage blood vessels, nerves, eyes and kidneys. Approximately 1 in 200 women of childbearing age has diabetes before getting pregnant (called preexisting diabetes). According to the March of Dimes, pregnant women with poorly controlled diabetes, especially preexisting diabetes, are at increased risk of certain pregnancy complications, including miscarriage, pregnancy-related high blood pressure, polyhydramnios (an excess of amniotic fluid, which can contribute to preterm labor), preterm delivery, serious birth defects, and stillbirth. High blood sugar in the first few weeks of pregnancy can increase the risk of birth defects, so early prenatal care is critical. However, the treatment of gestational diabetes has greatly improved and most women with the condition deliver healthy babies.

The biggest concern with gestational diabetes is that too much glucose will enter the baby’s bloodstream, causing it to gain too much weight, especially in the upper body, a condition called macrosomia. A macrosomic baby is too large to enter the birth canal, or the head may enter and the shoulders then get stuck. Your doctor will carefully monitor the size and health of your baby throughout your pregnancy, and especially during the third trimester. If your baby reaches a weight of 9 pounds, 14 ounces or more, your doctor may recommend you deliver by cesarean at term.

According to the March of Dimes, approximately 50 percent of women with gestational diabetes will develop it in future pregnancies, and 50 percent will develop type 2 diabetes within 5 years after delivery. Risk factors for future diabetes include:

• Obesity
• If you had very high blood sugar levels (especially if you needed insulin)
• Your diabetes was diagnosed early in your pregnancy
• The results of your postpartum glucose test were elevated, but not high enough to classify you as a diabetic.

Gestational diabetes is a serious risk to your health and that of your baby; however, with proper prenatal care, careful monitoring, and a healthy diet and exercise, you can ensure you and your baby will remain healthy.

For more information:

• Healthful Snacks
• Healthy Diet
• Benefits of Prenatal Exercise
• Find out what other women are saying about fitness during pregnancy.