Patient information: Gestational diabetes mellitus (Beyond the Basics)
- Lois Jovanovic, MD
Lois Jovanovic, MD
- Clinical Professor of Medicine
- Keck School of Medicine
- Adjunct Professor of Biomolecular Science and Engineering and Chemical Engineering
- University of California-Santa Barbara
- Section Editors
- David M Nathan, MD
David M Nathan, MD
- Editor-in-Chief — Endocrinology
- Section Editor — Diabetes Mellitus
- Professor of Medicine
- Harvard Medical School
- Michael F Greene, MD
Michael F Greene, MD
- Section Editor — Diabetes in Pregnancy
- Professor of Obstetrics and Gynecology
- Harvard Medical School
Gestational diabetes mellitus (GDM) is a condition that develops during pregnancy when the body is not able to make enough insulin. The lack of insulin causes the blood glucose (also called blood sugar) level to become higher than normal. Gestational diabetes affects between 2 and 10 percent of women during pregnancy.
It is important to recognize and treat gestational diabetes as soon as possible to minimize the risk of complications to mother and baby. In addition, it is important for women with a history of gestational diabetes to be tested for diabetes after pregnancy because of an increased risk of developing type 2 diabetes in the years following delivery.
More detailed information about gestational diabetes is available by subscription. (See "Diabetes mellitus in pregnancy: Screening and diagnosis".)
GESTATIONAL DIABETES TESTING
We recommend that all pregnant women be screened for gestational diabetes. Identifying and treating gestational diabetes can reduce the risk of pregnancy complications. (See "Diabetes mellitus in pregnancy: Screening and diagnosis".)
Complications of gestational diabetes can include:
●Having a large baby (weighing more than 9 lbs or 4.1 kg), which can increase the risk of injury to the mother or baby during delivery and increase the chance of needing a cesarean section
●Preeclampsia (see "Patient information: Preeclampsia (Beyond the Basics)")
Timing of test — Screening for gestational diabetes is usually done between 24 and 28 weeks of pregnancy. However, screening may be done earlier in the pregnancy if you have risk factors for gestational diabetes, such as:
●A history of gestational diabetes in a previous pregnancy
●Glucose (sugar) in your urine
●A strong family history of diabetes
Test procedure — There are a few ways to test for gestational diabetes.
Two part test — On the day of the screening test, you can eat and drink normally. You will be given 50 grams of glucose, usually in the form of a specially formulated orange or cola drink. You should drink the whole amount within a few minutes. One hour later, you will have a blood test to measure your blood sugar level.
If your blood sugar level is normal, no other tests are done.
Most doctors and nurses consider your blood sugar level to be high if it is higher than 130 to 140 mg/dL (7.2 to 7.7 mmol/L). If your blood sugar level is very high (higher than 200 mg/dL [11.1 mmol/L]), there is a very good chance that you have gestational diabetes.
If your blood sugar level is higher than normal, you will need another test to know for sure if you have gestational diabetes. This test is called an oral glucose tolerance test (GTT). The test is done by measuring your blood sugar level before you eat anything in the morning (fasting), then again one, two, and three hours after you drink a glucose drink that contains 100 grams of glucose (twice the amount in the one-hour test). Similar to the one-hour test, this is usually in the form of a specially formulated orange or cola drink.
Gestational diabetes is diagnosed if you have two or more elevated blood sugar values.
One part test — Some doctors screen for diabetes with a different type of oral glucose tolerance test (GTT). The test is done by measuring your blood sugar level before you eat anything in the morning (fasting), then again one and/or two hours after you drink a glucose drink that contains 75 grams of glucose. This is usually in the form of a specially formulated orange or cola drink.
Gestational diabetes is diagnosed if you have one or more elevated blood sugar values.
GESTATIONAL DIABETES TREATMENT
After you are diagnosed with gestational diabetes, you will need to make changes in what you eat, and you will need to learn to check your blood sugar level. In some cases, you will also need to learn how to give yourself insulin injections. (See "Gestational diabetes mellitus: Glycemic control and maternal prognosis".)
The main goal of treatment for gestational diabetes is to reduce the risk that the baby will be large (weigh greater than 9 lbs at birth). A large baby can be difficult to deliver through the pelvis (called “shoulder dystocia”). A vaginal delivery increases the risk of injuring a large baby (eg, broken bones or nerve injury). A large baby is also more likely to cause injury to the mother during the delivery.
You are more likely to have a large baby if your blood sugar levels are higher than normal during pregnancy.
Changes in diet — To learn what changes you should make in your diet, you will meet with a dietitian or nurse. The following are some general dietary recommendations:
●Avoid high-calorie snacks and desserts, including soda with sugar, fruit punch, candy, chips, cookies, cakes, and full-fat ice cream
●You can use artificial sweeteners, such as aspartame (Nutrasweet), sucralose (Splenda), stevioside (Stevia), or acesulfame potassium (Sunnet).
●These sweeteners have not been linked to an increased risk of birth defects.
●Eat a lot of vegetables and fruits, at least five servings a day. Some fruits (like grapes, dried fruit) can increase your blood sugar level excessively and should be eaten in limited amounts. Don’t eat a lot of starchy vegetables (eg, potatoes), but eat as many non-starchy fruits or vegetables as you like.
●Choose foods with whole grains. This includes whole-wheat bread, brown rice, or whole-wheat pasta instead of white bread, white rice, or regular pasta.
●If you eat red meat, eat a small amount and only a few times during the week. Choose lean cuts of meat that end in "loin" (eg, pork loin, tenderloin, sirloin). Remove skin from chicken and turkey before eating.
●Choose low- or fat-free dairy products, such as skim milk, nonfat yogurt, and low-fat cheese
●Use liquid oils (olive, canola) instead of solid fats (butter, margarine, shortening) for cooking
Blood sugar monitoring — You will learn how to check your blood sugar level and record the results (figure 1). Instructions for choosing a blood sugar meter, checking blood sugar levels at home, and ways to record the results are discussed separately. (See "Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)".)
Initially, most women should check their blood sugar level four times per day:
●Before eating in the morning
●One hour after breakfast, lunch, and dinner
This information can help to determine whether your blood sugar levels are on target. If your levels stay higher than they should be, your doctor will probably recommend that you start using insulin. (See 'Insulin' below.)
Once on insulin, you need to check your blood glucose levels six times a day: before and one hour after each meal.
Exercise — Although exercise is not a necessary part of gestational diabetes treatment, it might help to control blood sugar levels. If you were exercising before, you should continue after being diagnosed with gestational diabetes.
If you did not previously exercise, ask your doctor or nurse if exercise is recommended. Most women who do not have medical or pregnancy-related complications are able to exercise, at least moderately, throughout their pregnancy.
Insulin — Approximately 15 percent of women with gestational diabetes will require insulin. Insulin is a medicine that helps to reduce blood sugar levels and can reduce the risk of gestational diabetes-related complications. Insulin is the most common medicine for treating gestational diabetes.
You must give insulin by injection because it does not work when it is taken by mouth. Most women start by giving one shot of insulin per day. If your blood sugar levels are high after eating, you may need to give a shot two or three times per day. Instructions for drawing up and giving insulin shots are available separately. (See "Patient information: Diabetes mellitus type 2: Insulin treatment (Beyond the Basics)".)
If you take insulin, you should check your blood sugar level at least six times per day. You also need to write down your results and how much insulin you give and review these records at each prenatal visit (figure 1). Keeping accurate records helps to adjust insulin doses and can decrease the risk of complications.
Oral diabetes medicines, such as those taken by people with type 2 diabetes, are sometimes used during pregnancy in the United States. We prefer insulin therapy for women with diabetes who cannot control blood glucose levels adequately with nutritional therapy. Insulin is effective and safe. The oral diabetes medicines pass from the mother to her baby through the placenta; while they do not appear to harm the fetus or newborn, it is not known if there are longer-term effects on children. However, oral anti-hyperglycemic agents are a reasonable alternative for women who refuse to take, or are unable to comply with, insulin therapy.
MONITORING DURING PREGNANCY
Prenatal visits — Most women who develop gestational diabetes have more frequent prenatal visits (eg, once every week or two), especially if insulin is used. The purpose of these visits is to monitor your and your baby's health, discuss your diet, and adjust your dose of insulin to keep your blood sugar levels near normal. It is common to change the dose of insulin as the pregnancy progresses. (See "Gestational diabetes mellitus: Obstetrical issues and management".)
Nonstress testing — You may need tests to monitor the health of the baby during the last trimester of pregnancy, especially if your blood sugars have been high, you are using insulin, or if you have any pregnancy-related complications (eg, high blood pressure). The most commonly used test is the nonstress test. This test is discussed in a separate topic review. (See "Patient information: Postterm pregnancy (Beyond the Basics)".)
LABOR AND DELIVERY WITH GESTATIONAL DIABETES
If your blood sugar levels are close to normal during pregnancy and you have no other complications, the ideal time to deliver is between 39 and 40 weeks of pregnancy.
If you do not deliver by your due date, you may need additional testing to monitor your and your baby's health. (See "Patient information: Postterm pregnancy (Beyond the Basics)".)
In most women with a normal-size baby, there are no advantages to a cesarean delivery over a vaginal delivery. The risks and benefits of cesarean delivery are discussed separately. (See "Patient information: C-section (cesarean delivery) (Beyond the Basics)".)
Your blood sugar levels will be monitored during labor. Most women have normal blood sugar levels during labor and don’t need any insulin. Insulin is given if your blood sugar level becomes high. High blood sugar levels during labor can cause problems in the baby, both before and after delivery. (See "Pregestational and gestational diabetes: Intrapartum and postpartum glycemic control".)
After delivery, most women with gestational diabetes have normal blood sugar levels and do not require further treatment with insulin. You can return to your prepregnancy diet, and you are encouraged to breastfeed. (See "Patient information: Deciding to breastfeed (Beyond the Basics)".)
However, it is important to check your blood sugar level the day after delivery to be sure that it is normal or near normal. Pregnancy itself does not increase the risk of developing type 2 diabetes. However, having gestational diabetes does increase your risk of developing type 2 diabetes later in life.
If your blood sugar level is normal after delivery, you should have testing for type 2 diabetes at six weeks postpartum. Testing usually includes a two-hour glucose tolerance test (GTT).
Risk of gestational diabetes — One-third to two-thirds of women who have gestational diabetes in one pregnancy will have it again in a later pregnancy. Weight reduction through diet and exercise can reduce this risk.
Risk of type 2 diabetes — Women with gestational diabetes have an increased risk of developing type 2 diabetes later in life, especially if the woman has other risk factors (eg, obesity, family history of type 2 diabetes).
The risk of developing type 2 diabetes is greatly affected by body weight. Women who are obese have a 50 to 75 percent risk of type 2 diabetes, while women who are a normal weight have a less-than-25 percent risk. If you are overweight or obese, you can reduce your risk of type 2 diabetes by losing weight and exercising regularly.
The American Diabetes Association (ADA) recommends that all women with a history of gestational diabetes have testing for type 2 diabetes at least every three years after their pregnancy. Women who have gestational diabetes after age 45 should have testing once per year.
Birth control — Women with a history of gestational diabetes can use any type of birth control after pregnancy. A review of all of the birth control options is available separately. (See "Patient information: Birth control; which method is right for me? (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Preeclampsia (Beyond the Basics)
Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)
Patient information: Diabetes mellitus type 2: Insulin treatment (Beyond the Basics)
Patient information: Postterm pregnancy (Beyond the Basics)
Patient information: C-section (cesarean delivery) (Beyond the Basics)
Patient information: Deciding to breastfeed (Beyond the Basics)
Patient information: Birth control; which method is right for me? (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Clinical presentation and diagnosis of diabetes mellitus in adults
Effect of advanced age on fertility and pregnancy in women
Infant of a diabetic mother
Pregestational diabetes mellitus: Obstetrical issues and management
Diabetes mellitus in pregnancy: Screening and diagnosis
Gestational diabetes mellitus: Glycemic control and maternal prognosis
Gestational diabetes mellitus: Obstetrical issues and management
Pregestational and gestational diabetes: Intrapartum and postpartum glycemic control
The following organizations also provide reliable health information.
●National Library of Medicine
(www.nlm.nih.gov/medlineplus/ency/article/000896.htm, available in Spanish)
●National Institute of Diabetes and Digestive and Kidney Diseases
●American Diabetes Association (ADA)
- Crowther CA, Hiller JE, Moss JR, et al. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med 2005; 352:2477.
- Dodd JM, Crowther CA, Antoniou G, et al. Screening for gestational diabetes: the effect of varying blood glucose definitions in the prediction of adverse maternal and infant health outcomes. Aust N Z J Obstet Gynaecol 2007; 47:307.
- American Diabetes Association. Gestational diabetes mellitus. Diabetes Care 2004; 27 Suppl 1:S88.
- American College of Obstetricians and Gynecologists Committee on Practice Bulletins--Obstetrics. ACOG Practice Bulletin. Clinical management guidelines for obstetrician-gynecologists. Number 30, September 2001 (replaces Technical Bulletin Number 200, December 1994). Gestational diabetes. Obstet Gynecol 2001; 98:525.
- Löbner K, Knopff A, Baumgarten A, et al. Predictors of postpartum diabetes in women with gestational diabetes mellitus. Diabetes 2006; 55:792.
- Jovanovic, L (Ed). Diabetes and Pregnancy: What to Expect, American Diabetes Association, Alexandria, VA, revised 2007.
All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.