Approximately 3 to 5 percent of all pregnant women in the United States are diagnosed as having gestational diabetes.
Diabetes (actual name is diabetes mellitus) of any kind is a disorder that prevents the body from using food properly. Normally, the body gets its major source of energy from glucose, a simple sugar that comes from foods high in simple carbohydrates (e.g., table sugar or other sweeteners such as honey, molasses, jams, and jellies, soft drinks and cookies), or from the breakdown of complex carbohydrates such as starches (e.g., bread, potatoes, and pasta). After sugars and starches are digested in the stomach, they enter the blood stream in the form of glucose. For the purpose of this hypertext document the words sugar and glucose are used synonymously.The glucose in the blood stream becomes a potential source of energy for the entire body, similar to the way in which gasoline in a service station pump is a potential source of energy for your car. But, just as someone must pump the gas into the car, the body requires some assistance to get glucose from the blood stream to the muscles and other tissues of the body. In the body, that assistance comes from a hormone called insulin. Insulin is manufactured by the pancreas, a gland that lies behind the stomach. Without insulin, glucose cannot get into the cells of the body where it is used as fuel. Instead, glucose accumulates in the blood to high levels and is excreted or "spilled" into the urine through the kidney.
When the pancreas of a child or young adult produces little or no insulin we call this condition juvenile-onset diabetes or Type I diabetes (insulin-dependent). This is not the type of diabetes you have. Unlike women with Type I diabetes, women with gestational diabetes have plenty of insulin. In fact, they usually have more insulin in their blood than women who are not pregnant. However, the effect of their insulin is partially blocked by a variety of other hormones made in the placenta , a condition often called insulin resistance.
The placenta performs the task of supplying the growing fetus with nutrients and water from the mother's circulation. It also produces a variety of hormones vital to the preservation of the pregnancy. Ironically, several of these hormones such as estrogen, cortisol, and human placental lactogen (HPL) have a blocking effect on insulin, a "contra-insulin" effect. This contra-insulin effect usually begins about midway (20 to 24 weeks) through pregnancy. The larger the placenta grows, the more of these hormones are produced, and the greater the insulin resistance becomes. In most women the pancreas is able to make additional insulin to overcome the insulin resistance. When the pancreas makes all the insulin it can and there still isn't enough to overcome the effect of the placenta's hormones, gestational diabetes results. If we could somehow remove all the placenta's hormones from the mother's blood, the condition would be remedied. This, in fact, usually happens following a delivery.
There are several different types of diabetes. Gestational diabetes begins during pregnancy and disappears following delivery. Another type is referred to as juvenile-onset diabetes (in children) or Type I (in young adults). These individuals usually develop their disease before age 20. People with Type I diabetes must take insulin by injection every day. Approximately 10 percent of all people with diabetes have Type I (also called insulin-dependent diabetes).
Type II diabetes or noninsulin-dependent diabetes (formerly called adult-onset diabetes) is also characterized by high blood sugar levels, but these patients are often obese and usually lack the classic symptoms (fatigue, thirst, frequent urination, and sudden weight loss) associated with Type I diabetes. Many of these individuals can control their blood sugar levels by following a careful diet and exercise program, by losing excess weight, or by taking oral medication. Some, but not all, need insulin. People with Type II diabetes account for roughly 90 percent of all diabetes.
Any woman might develop gestational diabetes during pregnancy. Some of the factors associated with women who have an increased risk are obesity; a family history of diabetes; having given birth previously to a very large infant; a still birth, or a child with a birth defect; or having too much amniotic fluid (polyhydramnios). Also, women who are older than 25 are at greater risk than younger individuals. Although a history of sugar in the urine is often included in the list of risk factors, this is not a reliable indicator or who will develop diabetes during pregnancy. Some pregnant women with perfectly normal blood sugar levels will occasionally have sugar detected in their urine. The Council on Diabetes in Pregnancy of the American Diabetes Association strongly recommends that all pregnant women be screened for gestational diabetes. Several methods of screening exist. The most common is the 50-gram glucose screening test. No special preparation is necessary for this test, and there is no need to fast before the test. The test is performed by giving 50 grams of a glucose drink and then measuring the blood sugar level 1-hour later. A woman with a blood sugar level of less than 140 milligrams per deciliter (mg/dl) at 1-hour is presumed not to have gestational diabetes and requires no further testing. If the blood sugar level is greater than 140 mg/dl the test is considered abnormal or "positive." Not all women with a positive screening test have diabetes. Consequently, a 3-hour glucose tolerance must be performed to establish the diagnosis of gestational diabetes.
If your physician determines that you should take the complete 3-hour glucose tolerance test , you will be asked to follow some special instructions in preparation for the test. For 3 days before the test, eat a diet that contains at least 150 grams of carbohydrates each day. This can be accomplished by including one cup of pasta, two servings of fruit, four slices of bread, and three glasses of milk every day. For 10 to 14 hours before the test you should not eat and not drink anything but water. The test is usually done in the morning in your physician's office or in a laboratory. First, a blood sample will be drawn to measure your fasting blood sugar level. Then you will be asked to drink a full bottle of glucose drink (100 grams). This glucose drink is extremely sweet and occasionally makes some people feel nauseated. Finally, blood samples will be drawn every hour for 3 hours after the glucose drink has been consumed. The normal values for this test are shown in Table 1.
Table 1. 3-Hour Glucose Tolerance Test for Gestational Diabetes
If two or more of your blood sugar levels are higher than the diagnostic criteria, you have gestational diabetes. This testing is usually performed at the end of the second trimester or the beginning of the third trimester (between the 24th and 28th weeks of pregnancy) when insulin resistance usually begins. If you had gestational diabetes in a previous pregnancy or there is some reason why your physician is unusually concerned about your risk of developing gestational diabetes, you may be asked to take the 50 gram glucose screening test as early as the first trimester (before the 13th week). Remember, merely having sugar in your urine or even having an abnormal blood sugar on the 50-gram glucose screening does not necessarily mean you have gestational diabetes. The 3-hour glucose tolerance test must be abnormal before the diagnosis is made.
The complications of gestational diabetes are manageable and preventable. The key to prevention is careful control of blood sugar levels just as soon as the diagnosis of gestational diabetes is made.
You should be reassured that there are certain things gestational diabetes does not usually cause. Unlike Type I diabetes, gestational diabetes does not generally cause birth defects. For the most part, birth defects originate sometime during the first trimester (before the 13th week) of pregnancy. The insulin resistance from the contra-insulin hormones produced by the placenta does not usually occur until approximately the 24th week. Therefore, women with gestational diabetes generally have normal blood sugar levels during the critical first trimester.
One of the major problems a woman with gestational diabetes faces is a condition the baby may develop called "macrosomia." Macrosomia means "large body" and refers to a baby that is considerably larger than normal. All of the nutrients the fetus receives come directly from the mother's blood (figure 2). If the maternal blood has too much glucose, the pancreas of the fetus senses the high glucose levels and produces more insulin in an attempt to use this glucose. The fetus converts the extra glucose to fat. Even when the mother has gestational diabetes, the fetus is able to produce all the insulin in needs. The combination of high blood glucose levels from the mother and high insulin levels in the fetus results in large deposits of fat which causes the fetus to grow excessively large, a condition known as macrosomia. Occasionally, the baby grows too large to be delivered through the vagina and a cesarean delivery may become necessary. The obstetrician can often determine if the fetus is macrosomic by doing a physical examination. However, in many cases a special test called ultrasound is used to measure the size of the fetus. This and other special tests will be discussed later.
In addition to macrosomia, gestational diabetes increases the risk of hypoglycemia (low blood sugar) in the baby immediately after delivery. This problem occurs if the mother's blood sugar levels have been consistently high causing the fetus to have a high level of insulin in its circulation. After delivery the baby continues to have a high insulin level, but it no longer has the high level of sugar from its mother, resulting in the newborn's blood sugar level becoming very low. Your baby's blood sugar level will be checked in the newborn nursery and if the level is too low, it may be necessary to give the baby glucose intravenously. Infants of mothers with gestational diabetes are also vulnerable to several other chemical imbalances such as low serum calcium and low serum magnesium levels.
All of these are manageable and preventable problems. The key to prevention is careful control of blood sugar levels in the mother just as soon as the diagnosis of gestational diabetes is made. By maintaining normal blood sugar levels, it is less likely that a fetus will develop macrosomia, hypoglycemia, or other chemical abnormalities.
In addition to your obstetrician, there are other health professional who specialize in the management of diabetes during pregnancy including internists or diabetologists, registered dietitians, qualified nutritionists, and diabetes educators. Your doctor may recommend that you see one or more of these specialists during your pregnancy. In addition, a neonatologist (a doctor who specializes in the care of newborn infants) should also be called in to manage any complications the baby might develop after delivery.
On e of the essential components in the care of a woman with gestational diabetes is a diet specifically tailored to provide adequate nutrition to meet the needs of the mother and the growing fetus. At the same time the diet has to be planned in such a way as to keep blood glucose levels in the normal range (60 to 120 mg/dl). Specific details about diet during pregnancy are discussed later.
An obstetrician, diabetes educator, or other health care practitioner can teach you how to measure your own blood glucose levels at home to see if levels remain in an acceptable range on the prescribed diet. The ability of patients to determine their own blood sugar levels with easy-to-use equipment represents a major milestone in the management of diabetes, especially during pregnancy. The technique called "self blood glucose monitoring" (discussed in detail later) allows you to check your own blood sugar levels at home or at work without costly and time-consuming visits to your doctor. The values of your blood sugar levels also determine if you need to begin insulin therapy sometime during pregnancy. Short of frequent trips to a laboratory, this is the only way to see if blood glucose levels remain under good control.
Once you are diagnosed as having gestational diabetes, you and your health care providers will want to know more about your day-to-day blood sugar levels. It is important to know how your exercise habits and eating patterns affect your blood sugars. Also, as your pregnancy progresses, the placenta will release more of the hormones that work against insulin. Testing your blood sugar levels at important times during the day will help determine if proper diet and wait gain have kept blood sugar levels normal or if extra insulin is needed to help keep the fetus protected.
Self blood glucose monitoring is done by using a special device to obtain a drop of your blood and test it for your sugar level. Your doctor or other health care provider will explain the procedure to you. Make sure that you are shown how to do the testing before attempting it on your own. Some items you may use to monitor your blood sugar levels are:
Your health care provider can advise you where to obtain the self-monitoring equipment in your area. You may want to inquire if any place rent or loan glucose meters, since it is likely you won't be needing it after your baby is born.
You may need to test your blood several times a day. Generally, these times are fasting (first thing in the morning before you eat) and 2 hours after each meal. Occasionally, you may be asked to test more frequently during the day or at night. As each person is an individual, your health care provider can advise the schedule best for you.
Most manufacturers of glucose testing products provide a record diary, although some health care providers may have their own version. A Self Blood Glucose Monitoring Diary is included at the end of this document.
You should record any test result immediately because it's easy to forget what the reading was during the course of a busy day. You should always have this diary with you when you visit your doctor or other health care provider or when you contact them by phone. These results are very important in making decisions about you health care.
In addition to blood testing, you may be asked to check your urine for ketones. Ketones are by-products of the breakdown of fat and may be found in the blood and urine as a result of inadequate insulin or from inadequate calories in your diet. Although it is not known whether or not small amounts of ketones can harm the fetus, when large amounts of ketones are present they are accompanied by a blood condition, acidosis, which is known to harm the fetus. To be on the safe side, you should watch for them in your urine and report any positive results to your doctor.
To test urine for ketones, you can use a test strip similar to the one used for testing your blood. This test strip has a special chemically treated pad to detect ketones in the urine. Testing is done by passing the test strip through the stream of urine or dipping the strip in and out of urine in a container. As your pregnancy progresses, you might find it easier to use the container method. All test strips are disposable and can be used only once. This applies to blood sugar test strips also. You cannot use your blood sugar test strips for urine testing, and you cannot use your urine ketone test strips for blood sugar testing.
Overnight is the longest fasting period, so you should test your urine first thing in the morning every day and any time your blood sugar level goes to over 240 mg/dl on the blood glucose test. It is also important to test if you become ill and are eating less food than normal. Your health care provider can advise what is best for you.
Yes, despite careful attention to diet some women's blood sugar do not stay within an acceptable range. A pregnant woman free of gestational diabetes rarely has a blood glucose level that exceeds 100 mg/dl in the morning before breakfast (fasting) or 2 hours after a meal. The optimum goal for a gestational diabetic is blood sugar levels that are the same as those of a woman without diabetes.
There is no absolute blood sugar level that necessitates beginning insulin injections. However, many physicians begin insulin if the fasting sugar exceeds 105 mg/dl or if the level 2 hours after a meal exceeds 120 mg/dl on two separate occasions. Blood sugar levels measured by you at home will help your doctor know when it is necessary to begin insulin. The ability to perform self blood glucose monitoring has made it possible to begin insulin therapy at the earliest sign of high sugar levels, thereby preventing the fetus from being exposed to high levels of glucose from the mother's blood.
The ultimate concern of any expectant mother is, "Will my baby be all right?" There is an array of simple, safe tests used to assess the condition of the fetus before birth and these can be particularly valuable during a pregnancy complicated by gestationally diabetes. Tests that may be given during your pregnancy include:
Ultrasound. Ultrasound uses short pulses of high-frequency low-intensity sound waves to create the images. Unlike x rays, there is no radiation exposure to the fetus. First used during World War II to detect enemy submarines below the surface of the water, ultrasound has since been used safely in obstetrics. Occasionally, the date of your last menstrual period is not sufficient to determine a due date. Ultrasound can provide an accurate gestational age and due date that may be very important if it is necessary to induce labor early or perform a cesarean delivery. Ultrasound can also be used to determine the position of the placenta if it is necessary to perform an amniocentesis (another test discussed later).
Fetal movement records. Recording fetal movement is a test you can do by yourself to help determine the condition of the baby. Fetal activity is generally a reassuring sign of well-being. Women are often asked to count fetal movements during the last trimester of pregnancy. You may be asked to set aside specific times to lie down on your back or side and count the number of times the baby moves or kicks. Three or more movements in a 2-hour period is considered normal. contact your obstetrician if you feel fewer than three movements to determine if other tests are needed.
Fetal monitoring. Modern instruments make it possible to monitor the baby's hear rate before delivery. Currently, there are two types of fetal monitors-internal and external. The internal monitor consists of a small wire electrode attached directly to the scalp of the fetus after the membranes have ruptured. the external monitor uses transducers secured to the mother's abdomen by an elastic belt. One transducer records the baby's hear rate by a sensitive microphone called a Doppler. The other transducer measures the firmness of the abdomen during a contraction of the uterus. It is a crude measure of the strength and frequency of contractions. Fetal monitoring is the basis for the non-stress test and the oxytocin challenge test described below.
Non-stress test. The "non-stress" test refers to the fact that no medication is given to the mother to cause movement of the fetus or contraction of the uterus. It is often used to confirm the well-being of the fetus based on the principle that a healthy fetus will demonstrate an acceleration in its heart rate following movement. Fetal activity may be spontaneous or induced by external manipulation such as rubbing the mother's abdomen or making a loud noise above the abdomen with a special device. When movement of the fetus is noted, a recording of the fetal heart rate is made. If the heart rate goes up, the test is normal. If the heart rate does not accelerate, the fetus may merely be "sleeping": if, after stimulation, the fetus still does not react, it my be necessary to perform a "stress test" (oxytocin challenge test).
Amniocentesis. Amniocentesis is a method of removing a small amount of fluid from the amniotic sac for analysis. Either the fluid itself or the cells shed by the fetus into the fluid can be studied. In mid-pregnancy the cells in amniotic fluid can be studied for genetic abnormalities such as Down syndrome. Many women over the age of 35 amniocentesis for just this reason. Another important use for amniocentesis late in pregnancy is to study the fluid itself to determine if the lungs of the fetus are mature and able to withstand early delivery. this information can be very important in deciding the best time for a woman with Type I diabetes to deliver. It is not done as frequently to women with gestational diabetes.
Amniocentesis can be performed in an obstetrician's office or on an outpatient basis in a hospital. For genetic testing, amniocentesis is usually performed around the 16th week when the placenta and fetus can be located easily with ultrasound and a needle can be inserted safely into the amniotic sac. The overall complication rate for amniocentesis is less than 1 percent. The risk is even lower during the third trimester when the amniotic sac is larger and easily identifiable.
Many women with gestational diabetes can complete pregnancy and begin labor naturally. Any pregnant woman has a slight chance (about 5 percent) of developing preeclampsia (toxemia), a sudden onset of high blood pressure associated with protein in the urine, occurring late in pregnancy. If preeclampsia develops, your obstetrician may recommend an early delivery. When an early delivery is anticipated, an amniocentesis is usually performed to assess the maturity of the baby's lungs.
Gestational diabetes, by itself, is not an indication to perform a cesarean delivery, but sometimes there are other reasons your doctor may elect to do a cesarean. For example, the baby may be too large (macrosomic) to deliver vaginally, or the baby may be in distress and unable to withstand vaginal delivery. You should discuss the various possibilities for delivery with your obstetrician so there are no surprises.
Careful control of blood sugar levels remains important even during labor. If a mother's blood sugar level becomes elevated during labor, the baby's blood sugar level will also become elevated. High blood sugars in the mother produce high insulin levels in the baby. Immediately after delivery high insulin levels in the baby can drive its blood sugar level very low since it will no longer have the high sugar concentration from its mother's blood.
Women whose gestational diabetes does not require that they take insulin during their pregnancy, will not need to take insulin during their labor or delivery. On the other hand a woman who does require insulin during pregnancy may be given insulin by injection on the morning labor begins, or in some instances, it may be given intravenously throughout labor. For most women with gestational diabetes there is no need for insulin after the baby is born and blood sugar returns to normal immediately. the reason for this sudden return to normal lies in the fact that when the placenta is removed the hormones it was producing (which caused the insulin resistance) are also removed. Thus, the mother's insulin is permitted to work normally without resistance. Your doctor may want to check your blood sugar level the next morning, but it will most likely be normal.
One of the most frequently asked questions is, "Will my baby have diabetes?" Almost universally the answer is no. However, the baby is at risk for developing Type II diabetes later in life, and of having other problems related to gestational diabetes, such as hypoglycemia (low blood sugar) mentioned earlier. If your blood sugars were not elevated during the 24 hours before delivery, there is a good chance that hypoglycemia will not be a problem for your baby. Nevertheless, a neotatologist (a doctor who specializes in the care of newborn infants) or other doctor should check your baby's blood sugar level and give extra glucose if necessary.
Another problem that may develop in the infant of a mother with gestational diabetes is jaundice. Jaundice occurs when extra red blood cells in the baby's circulation are destroyed, releasing a substance called bilirubin. Bilirubin is a pigment that causes a yellow discoloration of the skin (jaundice). A minor degree of jaundice is common in many newborns. However, the presence of large amounts of bilirubin in the baby's system can be harmful and requires placing the baby under special lights which help get rid of the pigment. In extreme cases, blood transfusions may be necessary.
for most women gestational diabetes disappears immediately after delivery. However, you should have your blood sugars checked after your baby is born to make sure your levels have returned to normal. Women who had gestational diabetes during one pregnancy are at greater risk of developing it in a subsequent pregnancy. It is important that you have appropriate screening tests for gestational diabetes during future pregnancies as early as the first trimester.
Pregnancy is a kind of "stress test" that often predicts future diabetic problems. In one large study more than one-half of all women who had gestational diabetes developed overt Type II diabetes within 15 years of pregnancy. Because of the risk of developing Type II diabetes in the future, you should have your blood sugar level checked when you see your doctor for your routine check-ups. There is a good chance you will be able to reduce the risk of developing diabetes later in life by maintaining an ideal body weight and exercising regularly.
A nutritionally balanced diet is always essential to maintaining a healthy mother and successful pregnancy. the foods you choose become the nutrient building blocks for the growth of the fetus. For a woman with gestational diabetes, proper diet alone often keeps blood sugar levels in the normal range and is generally the first step to follow before resorting to insulin injections. Careful attention should be paid to the total calories eaten daily, to avoid foods which increase blood sugar levels, and to emphasize the use of foods which help the body maintain a normal blood sugar. A registered dietitian is the best person to help you with meal planning to meet your individual needs. Your physician can help you find a dietitian if this service is not a part of his or her office or clinic. Your local chapter of the American Dietetic Association or the American Diabetes Association can also help you locate a registered dietitian.
Of all questions asked by pregnant women, this is the most common. The answer is particularly important for women with gestational diabetes. The weight that you gain is a rough indication of how much nutrition is available to the fetus for growth. An inadequate weight gain may result in a small baby who lacks protective calorie reserves at birth. This baby may have more illness during the first year of life. An excessive weight gain during pregnancy, however, has an insulin-resistant effect, just like the hormones produced by the placenta, and will make your blood sugar level higher.
The "optimal" weight to gain depends on the weight that you are before becoming pregnant . Your pre-pregnancy weight is also a rough indication of how well-nourished you are before becoming pregnant. If you are at a desirable weight for your body size before you become pregnant, a weight gain of 24 to 27 pounds is recommended. If you are approximately 20 pounds or more above your desirable weight before pregnancy, a weight gain of 24 pounds is recommended. Many overweight women, however, have health babies and gain only 20 pounds. If you become pregnant when you are underweight, you need to gain more weight during the pregnancy to give your baby the extra nutrition he or she needs for the first year. You should gain 28 to 36 pounds, depending on how underweight you are before becoming pregnant.
Total recommended weight gain is often not as helpful as a weekly rate of gain. Most women gain 3 to 5 pounds during the first trimester (first 3 months) of pregnancy. During the second and third trimesters, a good rate of weight gain is about three-quarters of a pound to one pound per week. Gaining too much weight (w or more pounds per week) results in putting on too much body fat. This extra body fat produces an insulin-resistant effect which requires the body to produce more insulin to keep blood sugar levels normal. An inability to produce more insulin ,as in gestational diabetes, cause your blood sugar levels to rise above acceptable levels. If weight gain has been excessive, often limiting weight gain to approximately three-quarters of a pound per week (3 pounds per month) can return blood sugar levels to normal. Fetal growth and development depend on proper nourishment and will be placed at risk by drastically reducing calories. However, you can limit weight gain by cutting back on excessive calories and by eating a nutritionally-sound diet that meets your needs and the needs of your baby. Remember that dieting and severely cutting back on weight may increase the risk of delivering prematurely. If blood sugar levels continue to go up and you are not gaining excessive weight or eating improperly, the safest therapy for the well-being of the fetus is insulin.
Occasionally, your weight may go up rapidly in the last trimester (after 28 weeks) and you may notice an increase in water retention, such as swelling in the feet, fingers, and face. If there is any question as to whether the rapid weight gain is due to eating too many calories or too much water retention, keeping records of how much food you eat and your exercise patterns at this time will be very helpful. A food and Exercise Record Sheet is included at the end of this book. By examining your Food and Exercise Record Sheet, your nutrition advisor can help you determine which is causing the rapid weight gain. In addition, by examining your legs and body for signs of fluid retention, your physician can help you to determine the cause of your weight gain. If your weight gain is due to water retention, cutting back drastically on calories may actually cause more fluid retention. Bed rest and resting on your side will help you to lose the build-up of fluid. Limit your intake of salt (sodium chloride) and very salty foods, as they tend to contribute to water retention.
Marked fluid retention when combined with an increase in blood pressure and possibly protein in the urine are the symptoms of preeclampsia. This is a disorder of pregnancy that can be harmful to both the mother and baby. Inform your obstetrician of any rapid weight gain, especially if you are eating moderately and gaining more than 2 pounds per week. Should you develop preeclampsia, be especially careful to eat a well-balanced diet with adequate calories.
After being diagnosed as having gestational diabetes, many women notice a slow weight gain as they start cutting the various sources of sugar out of their diet. This seems to be harmless and lasts only 1 or 2 weeks. It may be that sweets were contributing a substantial amount of calories to the diet.