Gestational Diabetes
August 9, 1999 27 minutes read
Gestational Diabetes
Author: Robin M. Clemons, MD, MPH, Assistant Professor, Department of Family Medicine, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Stratford, NJ.
Peer Reviewer: Joyce M. Stein, DO, Krane and Milicia Obstetrics and Gynecology, City Line Avenue Hospital and Hahnemann University, Hospital of the Tenet System, Philadelphia, PA. Editor’s Note—Gestational diabetes is defined as a carbohydrate intolerance of variable severity with onset or first recognition during pregnancy.1-4 It is an asymptomatic state.5 This definition includes patients who had diabetes but who weren’t previously screened or diagnosed. Diabetes can also be pre-existing or pregestational.6 There is type 1 (formerly known as insulin-dependent diabetes mellitus), and type 2 (noninsulin-dependent diabetes mellitus).6 About 90% of pregnancies complicated by diabetes fall into the category of gestational diabetes.7
The prevalence of gestational diabetes mellitus ranges from 1.4-12.3% in the United States, depending on the population being studied.1,7-10 The incidence of type 1 diabetes in pregnancy is 0.2%, and type 2 diabetes in pregnancy is 0.3%.1,8
Risk factors that influence the frequency of gestational diabetes include increasing maternal age (> 30); maternal obesity (> 90 kg or 200 lbs); a family history of either type 1, type 2, or gestational diabetes; and race/ethnicity (particularly Latinos, Native Americans, Indians, and southeast Asians).11 Other risk factors include multiparity, and having an abnormal history in previous pregnancies of problems such as macrosomia, unexplained fetal demise, congenital anomalies, and multiple spontaneous abortions.11
Although most primary care providers do refer their patients with gestational diabetes for management, there are many instances where co-management and management with consultation are the only treatment options. Hence, primary care providers need this information. Management strategies include diet, exercise, and, in some cases, insulin therapy.
Morbidity of Gestational Diabetes
Gestational diabetes is a known risk factor for adverse pregnancy outcomes. Pregnancies complicated with gestational diabetes have an increased risk of maternal and perinatal complications, long-term maternal morbidity, and morbidity to the offspring. Perinatal morbidity and mortality are higher in pregnancies complicated by gestational diabetes. Although the rate of congenital defects is high in patients with pregestational diabetes, in pregnancies complicated by gestational diabetes the rate of congenital defects appears to be similar to the normal pregnant population.1 This has been hypostulated to be secondary to women with gestational diabetes having normal glucose tolerance during the first trimester when important organogenesis occurs in the fetus.
The causes of perinatal morbidity are neonatal hypoglycemia, hyperbilirubinemia, hypocalcemia, polycythemia, macrosomia birth weight more than 9 lbs (or 4 kg), and with that the problem shoulder dystocia, an abnormal apgar score, and Erb’s palsy (see Table 1).1
The causes of maternal morbidity in pregnancies complicated by gestational diabetes are an increased rate of c-section, and with it increased complications from that procedure such as postpartum endometritis, pain, postpartum hemorrhage, and an increased number of days off work.12 In addition, there has been a correlation with an increased incidence of pre-eclampsia and hypertensive disorders, as well as polyhydramnios.11,12
Long-term studies of patients with gestational diabetes show that these women are at risk of developing type 2 diabetes later in life.11,12 O’Sullivan, in a 20-year follow-up study, showed that 40% of women diagnosed with gestational diabetes develop type 2 diabetes mellitus.14 Other studies of patients carried out for five years postpartum by Mestman found an incidence of 55% of these women developing diabetes. In another study carried out 15 years after the diagnosis of gestational diabetes the incidence went up to 60%.15
There are some exciting studies on long-term follow-up of the offspring of these mothers, particularly looking at the development of diabetes, hypertension, and obesity in these children, their neuropsychological development, and correlating these data with the degree of maternal glycemic control and lipid metabolism.6,16 It appears that childhood obesity, higher blood pressure, glucose intolerance, and lower than expected intellectual and psychomotor development are related to the metabolic control of diabetes in both gestational and pregestational diabetics during pregnancy.16
| Table 1. Risk Factors for Gestational Diabetes |
| • Maternal age older than 30 years |
| • Pregravid weight more than 90 kg |
| • Family history of diabetes |
| • Race |
| • Multiparity |
| • Macrosomia |
Determinants of Gestational Diabetes
The causes of this condition are believed to be multifactorial. In normal nonobese women, pregnancy produces a greater than normal sensitivity to insulin during the first trimester in comparison to the second and third.2,17 Other studies confirmed these findings and, in addition, showed an increase in insulin secretion during glucose tolerance testing. This may be due to hormonal factors such as increased plasma estrogen levels.2,17 Increased insulin with normal to increased tissue sensitivity produces increased lipogenesis.2 Other hormonal changes that are known to occur during early pregnancy include increases in serum cortisol and progestins, which, in addition to estrogen, encourage fat accumulation.2 This could be a preparation for the increased energy needs of the second and third trimesters.2
Later in pregnancy the situation changes. Fetal growth is accelerated. The hormonal milieu changes so that human chorionic somatomammotropin (fetal placental lactogen) increases and, along with it, the tissue response to insulin decreases.2 Although insulin output has been shown to increase from hepatic tissue, insulin resistance increases as much as 50% in muscle tissue.2 These changes could be due to increases in prolactin, human chorionic somatomammotropin, cortisol, progesterone, estrogen, and the hyperplasia of pancreatic islet cells that occurs during late pregnancy.2,17,18 This, along with proliferating nutrition demands by increasing fetal growth, leads to the continuous withdrawal of nutrients from the maternal circulation.2
In summary, the hormonal changes in early and late pregnancy are designed to provide a constant supply of glucose for the fetus.
Because of increased fetal needs, gluconeogenesis needs to be enhanced during late pregnancy. This cannot be fueled by protein stores from muscle, as they are low in the maternal circulation during this time.2 So, gluconeogenesis is fueled by fat metabolism.2
Metabolic, islet cell, and hormonal changes during pregnancy, age, race/ethnicity, body habitus, plus genetically determined insulin resistance combine to produce gestational diabetes.2,17 Insulin resistance, insulin secretion, and hyperglycemia are all increased in the second and third trimesters in gestational diabetes when compared to normal pregnant women.2 Increases in serum glucose develop from hepatic glucose production (gluconeogenesis) as well as peripheral insulin resistance.2
Islet cell antibodies may play a role in the development of this condition. In a study from Spain, women diagnosed as having gestational diabetes were more likely to have islet cell antibodies (13%) than women from the general population. This subset of women were also at greater risk of developing type 1 diabetes later in life.17,19
Also, there are certain nutrients needed to facilitate pancreatic function, which can become depleted during pregnancy. Chromium, magnesium, potassium, and pyridoxine help to preserve pancreatic function and increase insulin sensitivity. Supplementation of these nutrients as a means of reduction of symptoms, treatment, or prevention of gestational diabetes needs to be analyzed in large-scale studies.20
Diagnosis of Gestational Diabetes
There are no internationally accepted criteria for diagnosing gestational diabetes mellitus. The diagnosis of gestational diabetes is usually accomplished early in the third trimester of pregnancy. This is because the problem is not easily diagnosed before the 24th week of gestation. The data in the figure are from a study on 84 pregnant diabetic women.15 Their amniotic fluid was analyzed for insulin content from 16-40 weeks of gestation. The insulin content of the amniotic fluid started to increase between the 24th and 28th weeks of gestation. From these data, it is apparent that the carbohydrate intolerance or insulin resistance worsens around 24-28 weeks.15
A number of organizations offer differing recommendations on how to diagnose gestational diabetes. In the United States we use the one-hour glucola test as a screening test (see table 4).
Nonfasting women are given 50 grams of glucose in a flavored solution, and their blood is taken one hour after ingestion. If the blood sugar equals or exceeds 140 mg/dL, then women are asked to take a three-hour glucose tolerance test (GTT) (see Table 5).4
For the three-hour GTT, women are advised to consume an unrestricted diet containing at least 150 grams of carbohydrates daily three days prior to testing. They are asked to fast for 10-14 hours prior to testing. All tests are performed in the morning. Women are asked to refrain from activity during the test, and not to smoke. Blood is drawn fasting and at 1, 2, and 3 hours postingestion of a 100-gram glucose-containing solution. If any two (out of 4) or more results are abnormal, then they are diagnosed as having gestational diabetes (see table 5).4
The importance of the three days of unrestricted diet has to be stressed. Starvation has been shown to produce a decreased tolerance to glucose in studies that demonstrated this in human and animal subjects.21,22,23 These subjects were given a three-hour GTT after receiving diets low in carbohydrates. Then, after they were given a 150-mg carbohydrate diet daily for four or five days, the test was repeated. When the individual test results were compared, the low carbohydrate diet impaired glucose tolerance to diagnostic levels. More patients had abnormal tests after starvation, which subsequently improved on refeeding.21,23
| Table 2. Causes of Perinatal Morbidity |
| • Neonatal hypoglycemia |
| • Hyperbilirubinemia |
| • Hypocalcemia |
| • Polycythemia |
| • Macrosomia |
| • Shoulder dystocia |
| • Abnormal APGAR |
| • Erb's palsy |
The following are the criteria for diagnosis of gestational diabetes and the organizations that recommend them.
ADA and ACOG Criteria
Screening of pregnant women at 24-28 weeks gestation with a 50 gm one-hour glucose screening test (1-hour glucola).3,24 Values of 140 mg/dL (7.8 mmol/L) or greater are considered abnormal. All abnormal tests are followed by a 100 gm three-hour GTT.3 Any two or more abnormal values are diagnostic of gestational diabetes.3
The World Health Organization and European Association for the Study of Diabetes Criteria
The World Health Organization (WHO) criteria are used mostly in Europe. They define diabetes in the general population and were not specifically developed for gestational diabetes. However, in a study of 1000 gravidas who were given a 75 gm two-hour oral glucose tolerance test (OGTT), the European Association for the Study of Diabetes concluded that diabetes should be diagnosed using WHO criteria.4,17 They are as follows:
The patient is given a 75 gm OGTT. Venous blood is then sampled at one and two hours after ingestion. A fasting blood sugar of 140 mg/dL (7.8 mmol/L) or a two-hour postprandial blood sugar of 200 mg/dL (11.1 mmol/L) is diagnostic of gestational diabetes.
National Diabetes Data Group Criteria
The National Diabetes Data Group criteria are based on the patient receiving a 100 gm three-hour GTT.3 Results are derived from plasma or serum glucose determined by the glucose oxidase method. They are as follows:3,4
Fasting 5.83 mmol/L (105 mg/dL)
1 hour 10.56 mmol/L (190 mg/dL)
2 hour 9.17 mmol/L (165 mg/dL)
3 hour 8.06 mmol/L (145 mg/dL)
| Table 3. Causes of Maternal Morbidity |
| • NIDDM |
| • C-Section |
| • Complications from instrumented deliveries |
Any two or more abnormal results are diagnostic of gestational diabetes.
Management
The goal of management in this condition is to reduce perinatal morbidity and mortality through controlling the blood sugar level of the prenatal patient with gestational diabetes. Management of gestational diabetes is best accomplished using a team approach. This team could consist of physicians (obstetrician, endocrinologist, perinatologist), diabetes educators, nutritionists, nurses, midwives, or nurse practitioners and, in some cases, a pharmacist.25
When patients are first told that they may have gestational diabetes they may experience some denial; others avoid further testing as a way of postponing or avoiding what they consider obnoxious treatments. A team approach can help these patients accept their diagnosis and receive treatment promptly (just because they hear the information from more than one authoritative source).
Patient Education
Educating the patient about her condition and its management, without alarming her, can go a long way to improve compliance. Your patient needs to understand what gestational diabetes is, and why it is important to her and her baby’s health. She needs to understand what the dietary and exercise recommendations are, and how to implement these into her daily life. She also needs to know how to perform glucose monitoring, when to check her blood sugar, as well as when and how these results should be communicated to you. She may also need to learn how to give herself insulin injections, how to prevent hyper- and hypoglycemia, and what to do should these problems occur.25 Organizations such as the March of Dimes, ACOG, AAFP, and the ADA have produced patient education materials that you may wish to review for your patient’s use.
Dietary Management
There is a great deal of controversy about what constitutes the ideal diet for women with gestational diabetes. The number of calories and the composition of these calories into macronutrients such as percentage of protein, percentage of carbohydrate, and percentage of fat are described in tables 7 and 8. However, how many meals per day and how many snacks per day that these calories should be optimally divided into to promote euglycemia and prevent the complications of gestational diabetes has yet to be determined.
There is some evidence that having your patient consume some calories on an hourly basis can lead to her needing less insulin over 24 hours (thereby decreasing insulin resistance).2 Your patient will probably appreciate this in late pregnancy, when her stomach capacity is diminished and there is decreased gastric emptying due to the enlarging uterus.7 However, the long-term studies to demonstrate that this dietary plan leads to fewer complications for the mother and infant have yet to be accomplished. What seems better tolerated by patients is a meal schedule that looks somewhat like the one they use in the nonpregnant state, which would consist of three meals a day with one or two snacks interspersed as well as a snack after dinner.27
Nutritional goals are to achieve normal blood sugar levels while providing adequate caloric intake for normal growth and development, without hyperglycemia or ketonemia.26 This is best done by consulting a nutritionist who is familiar with the patient’s cultural (and culinary) milieu.28,29 Goal attainment is monitored by glucose monitoring, following the patient’s pattern of weight gain, as well as dietary reassesment in order to determine if the nutritional needs of pregnancy are being met.13,28
Specific dietary prescriptions depend on the patient’s pre-pregnancy weight (whether she is under, normal, or overweight), her height, activity level, as well as her individual dietary and exercise habits.13,28 It is a good idea to have your patient start a diet diary prior to seeing the nutritionist (if this does not delay therapy).
Initial dietary recommendation should consist of a dietary intake of 35 kcal/kg of ideal body weight for most nonunderweight, nonobese patients (see Table 8).7,29 It is not recommended that obese patients lose weight during pregnancy; however, excessive weight gain should be avoided. Generally a diet consisting of complex carbohydrates (as opposed to simple sugars), soluble fiber, low in fat, while reduced in saturated fats, is recommended.1,12,30 Other researchers state that because gestational diabetes is a short-term disease, restriction of fats and protein to prevent long-term heart and kidney complications (as we do in treatment of diabetes in the nonpregnant population) is unnecessary.7
Although the proportion of nutrients remains controversial, one consistent recommendation is to limit carbohydrates during the morning meal because glucose tolerance is diminished in the early morning hours.7,29 Control of blood sugar in gestational diabetes is correlated to the percentage of calories from carbohydrates ingested.1 A handout for your patients describing dietary recommendations for this condition is found at the end of this article.
| Table 4. Screening for Gestational Diabetes |
| • One-hour glucola |
| • Patients do not have to be fasting |
| • One screening should be performed between 24 and 28 weeks |
| • Patients are given 50 g of glucose orally |
| • A blood glucose is drawn at one hour |
| • A blood sugar of 140 mg/dL or greater is considered positive |
| Note: It may be beneficial to screen high-risk women earlier in pregnancy |
| Table 5. Three-Hour Glucose Tolerance Test | |||
| Venous plasma | Venous whole blood | Capillary whole blood | |
| Fasting | 105 | 90 | 90 |
| 1 hour | 190 | 170 | 170 |
| 2 hour | 165 | 145 | 145 |
| 3 hour | 145 | 125 | 125 |
Exercise Management
Nonweight-bearing aerobic exercise is recommended for pregnant diabetics. The activity should be one that the patient enjoys, such as walking, bicycling, or swimming. It should be gradually added to your patient’s schedule, starting slowly for 5-10 minutes a session, and gradually increased in length. Each session is preceded with a 5-10 minute warm-up and ended with a 5-10 minute cool-down period. During the warm-up and cool-down periods, the patient should perform slow aerobic activity such as strolling or walking. Slow movements, such as pedaling slowly for bicycling or gliding for swimming activities, are also acceptable. The cool-down period is usually ended with stretching the muscles in long, slow movements.
The theory behind exercise therapy is that it uses the glucose, controls weight gain, alters hyperlipidemia, and alters the tissue sensitivity to endogenous insulin.7,9 Exercise also has important psychological benefits as well.7
The ideal exercise goals for women with gestational diabetes have not yet been determined. How much of what activities, to what intensity, for what length of time that will normalize blood glucose and reduce macrosomia, without leading to hypoglycemic events, is still being studied.
The controversy regarding exercise in pregnancy concerns possible fetal distress as measured by fetal heart rate, maternal uterine activity and blood flow, and infant birth weight.1
However, since exercise is recommended for diabetic control in the nonpregnant state and has been shown to decrease tissue insulin resistance, the current recommendation is to not discourage currently active women. Regular cardiovascular exercise should be continued (as opposed to sporadic exercise activities), as long as these activities are not contraindicated (see table 9).13,39,40 Activities studied in pregnant diabetics in the past are recumbent bicycling and arm ergometer training.9,28
Participation in aerobic activities three to four days per week for 15-30 minutes per session may be beneficial. Intensity should be monitored by having the patient take her pulse frequently. This should not exceed 70-80% of her maximal heart rate adjusted for her age (target heart rate = [220 - age] ´ 70%).27 This will be between 130-150 for most prenatal patients.
Insulin and Other Medications
The criteria for insulin therapy are failure of dietary and exercise management. If the fasting blood sugar is greater than 95, if the one-hour postprandial blood sugar is equal to or greater than 140, or if the two-hour postprandial blood sugar is equal to or greater than 120, then the patient needs tighter control of the blood sugar.
Human insulin is the drug of choice for treatment of gestational or pregestational diabetes.7,29 Oral hypoglycemic agents have been contraindicated for use in pregnancy due to possible teratogenic effects and prolonged fetal hyperinsulinemia.10 Insulin dosing of 0.7-1.0 U/kg, depending on the patient’s week of gestation (longer gestation usually requiring the higher dose), is also commonly recommended.10,27 Your patient may require multiple doses of short-acting or regular insulin before meals, or a combination of long-acting NPH with regular insulin.10,29 Insulin doses are adjusted frequently to achieve treatment goals (see table 10). An evening dose of long-acting NPH may be helpful for persistent fasting hyperglycemia.
Glycosylated Hemoglobin
HbA1C, or glycosylated hemoglobin levels, have not been useful in following gestational diabetics.8 This is probably due to the level of control necessary to prevent complications of gestational diabetes, which differs from the control in nonpregnant diabetics.8
Other reasons include that the normal level for fasting blood sugar as well as postprandial blood sugar are different than in nonpregnancy diabetics (fasting values are lower in the pregnant state).8 There is increased erythropoesis in pregnancy that also changes glycosylated hemoglobin values.8 Apparently the glucose impairment from gestational diabetes happens only during a short period (24 weeks gestation and beyond), making a two- to three-month average in HbA1C less practical.8
Blood Glucose Monitoring
In gestational diabetes the blood sugar should be checked at least four times daily.1 Patients should be encouraged to obtain and taught to use a home glucometer. The fasting blood sugar should not exceed 95 mg/dL and the two-hour postprandial blood sugar should not exceed 120 mg/dL.1,31
Home blood glucose monitoring, even in diet-controlled patients, can be advantageous because it makes our patients more mindful of the effect of their behavior on their blood sugar, thereby improving compliance with nonpharmacologic recommendations for glucose control.26 This gives you, the provider, a clear look into the patient’s level of glucose control over the past 24 hours, and allows you to make adjustments in diet, exercise, or medication as necessary to keep control of blood sugar as tight as possible.26
| Table 6. Three-Hour Glucose Tolerance Test |
| • The patient should have an unrestricted diet of at least 150 g of carbohydrates for three days preceding the test |
| • Test in the morning |
| • Fast for 10-14 hours before the test |
| • Patients are seated (and not smoking) during the test |
| • A blood glucose is drawn fasting, at 1 hour, at 2 hours, and at 3 hours |
| Table 7. Nutrients | |
| Carbohydrates | 38-45% |
| Protein | 20-25% |
| Fat | 30-40% |
Fetal Surveillance
Controversy surrounds when testing for fetal well-being should commence. Some recommend as early as 28 weeks, others start at 36 weeks.31 Some recommend starting at the earlier date in diabetics with poor control or those with co-morbidities such as vascular or hypertensive disease, or a history of previous stillbirth.25 In a meta-analysis looking at the effectiveness of fetal surveillance in predicting adverse outcomes in diabetic pregnancies, Fuentes and Chez concluded that there were insufficient data to support a specific time in pregnancy to begin fetal surveillance testing in patients with well-controlled diabetes class A through D without other obstetric complications.32
This lack of consensus allows us to use a more flexible, individualized approach to the third trimester evaluation of our patients. It also reflects the uncertainty of scientific evidence that should be shared with the patient. Perinatal complications in diabetic pregnancies can be prevented with a combination of early detection and strict metabolic control.33 Detecting macrosomia, early induction of labor (based on ultrasonic and clinical estimation of fetal weight), and use of c-section (when induction fails) may help to avoid traumatic birth in these pregnancies.34 The possibility of c-section should be discussed with your patient and their family early to avoid conflict near the end of gestation or during labor.
Opinions on how to test for fetal well-being also vary. Some do simple kick counts, others nonstress tests, and still others recommend biophysical profiles.
Kick counts, started as early as 28 weeks gestation, are a simple low-tech, inexpensive way of measuring fetal well-being. After experiencing a stillbirth, most mothers recant a history of decreased or absent fetal movement prior to the event. If medical intervention can occur quickly during this period of decreased fetal movement, perhaps this tragic outcome could be prevented. Kick counts are usually done after a meal or snack. Your patient lies on her left side and counts the number of fetal movements over a one-hour period. When she gets to 10 movements or kicks, she has accomplished a reassuring test of fetal well-being (and can now get up and do something else with her time).
Ultrasonography is particularly useful in diagnosing abnormalities in fetal growth (such as macrosomia, intrauterine growth retardation, or polyhydramnios) and may be a useful tool where these conditions are suspected. Scanning the crown rump length in the first trimester can confirm your patient’s dates. Other physicians advocate scanning between 16-22 weeks gestation to confirm dates and exclude any major congenital malformations (thereby eliminating doing 2).10,30
Fetal ultrasonography used in the third trimester can give you an estimated fetal weight and allow measurement of the abdominal circumference. Abdominal circumference below the 90th percentile for gestational age between 29-33 weeks gestation has been correlated with a less than 5% risk of delivering a large for gestational age (LGA) infant in patients with good dietary control.35
A maternal serum alpha-fetal protein level is important at 16-18 weeks because of the increased incidence of open neural tube defects in diabetic pregnancies.10
Nonstress testing is also used to evaluate fetal well-being of pregestational or gestational diabetic pregnancies. The antepartum fetal heart rate is monitored in response to spontaneous contractions, noise, and cervical stimulation. Two accelerations of the heart rate from the baseline over a 20-minute period of monitoring is a favorable response.10
Biophysical profiles are helpful because they combine ultrasonography with nonstress testing. This allows evaluation of amniotic fluid volume as well as abnormalities in fetal growth or development that may have gone undetected earlier in pregnancy.10 A score is derived from observing fetal activity, tone, breathing, and amniotic fluid. A score of 8 or above is reassuring.
Labor and Delivery
Timing of delivery is important. Delivery before term can lead to respiratory distress syndrome in the newborn, and should be avoided. Delivery after 38 weeks increases the probability of the infant developing macrosomia. Unless the pregnancy is complicated by macrosomia, polyhydramnios, poor control of diabetes, or other obstetrical indications (such as pre-eclampsia or intrauterine growth retardation), delivery at term is recommended.25
The policy of premature delivery in women with diabetes developed because of the association of gestational diabetes and late fetal demise. Current studies performed on women with pregestational and gestational diabetes have shown that the critical factor in deciding the timing of delivery was the degree of diabetic control (macrosomia and polyhydramnios being indicators of suboptimal control).6 Your patients with gestational diabetes can be allowed to deliver at term without increased perinatal and maternal risk, provided that the diabetes is well controlled, intensive fetal surveillance is reassuring, and there are no other obstetric indications for early delivery.
If delivery is decided on prior to 38 weeks, the need for amniocentesis to evaluate lung maturity will depend on the urgency for delivery. A lecithin to sphingomyelin (L/S) ratio of 2 or greater along with the presence of phosphatidylglycerol is what is recommended as being indicative of lung maturity for elective delivery before 38 weeks.6,30 After 38 weeks, if your patient has good dates and had a first or second trimester ultrasound that confirms the gestational age, an amniocentesis does not need to be performed.
With good diabetic control and no other obstetric complications, your patient with gestational diabetes should be able to continue her pregnancy to term, and may be able to avoid c-section. There is some evidence that prolonging pregnancy beyond 40 weeks may be detrimental.30
Inform your patient of the benefits of induction if she does not spontaneously go into labor between 39 and 40 weeks.31 At 40 weeks if her cervix is unfavorable, prostaglandin agents may be necessary to help ripen her cervix.31
Diabetes management during labor requires good control of blood sugar while avoiding hypoglycemia. Commonly your patient in labor is only taking in liquids, yet using energy during labor. Because of this, her insulin requirements are diminished. Many patients require no insulin during labor.31 Blood sugar should be checked every 1-2 hours during labor.24,31 Dextrose will need to be given intravenously if your patient’s blood sugar falls below 70 mg/dL (4.0 mmol/L). Short-acting regular insulin may need to be given intravenously for blood sugars rising above 140 mg/dL (7.8 mmol/L).31
Fetal monitoring should be performed as well as fetal blood sampling if indicated.30 You may want the extra skill of a neonatologist or pediatrician to help with neonatal resuscitation if necessary.25
| Table 8. Energy Requirements | ||||
| Pregravid Weight category | % Ideal bodyWeight | Pregravid Body Mass Index | Recommended Kcal/Kg | Recommended Weight Gain |
| Underweight | < 80% |
< 19.8 |
35-40 |
28-40 lbs |
| Normal weight | 80-120% |
19.8-26 |
30-35 |
25-35 lbs |
| Overweight | 121-150% |
26-29 |
25-35 |
15-25 lbs |
| Obese | > 151% |
> 29 |
25-35 |
at least 15 lbs |
| Reprinted with permission from the National Academy of Sciences. Nutrition During Pregnancy. Washington, DC: National Academy Press; 1990. | ||||
Postpartum Care
Insulin requirements decrease after the placenta has been delivered. If the patient was on an insulin infusion during labor the dose should be cut in half at this time. Also, breast feeding may reduce your patient’s insulin requirements by 25%.30 For patients with pregestational diabetes you can reinstitute the pre-pregnancy insulin dose as the patient is able to eat. Your patient needs the additional caloric requirements of breast feeding to be included in her diet postpartum, as hypoglycemia decreases milk production.31
It is important to stress the long-term complications of gestational diabetes with your patients. They need to know the importance of proper diet (low in concentrated sweets, high in fiber), exercise, controlling their weight, and controlling their lipids in prevention or delaying the onset of type 2 diabetes, as well as reducing cardiovascular risk in the future.5,6,26 Your patients also need to be educated about the symptoms of diabetes so that they can present themselves for screening and treatment early.36 Some authors recommend routine screening of postpartum women for diabetes at six weeks and at regular intervals (every 2 years in low-risk patients).25,36,37
Although your patients are probably counseled on birth control options during prenatal visits, postpartum is the time when these plans are implemented. Barrier methods are good alternatives for motivated couples, but may not be well suited to the lifestyles of the majority of your patients.37 Intrauterine devices can be used by your patient using the same indications and precautions as you would in other individuals (parous women in monogamous, stable relationships).37 Oral contraceptives tend to decrease insulin sensitivity and compromise insulin secretion in women with a history of gestational diabetes.37 However, subsequent pregnancy in women with a prior history of gestational diabetes also increases the risk of developing type 2 diabetes.5 The progesterone-only pill has no significant effect on carbohydrate or lipid metabolism and can be used during breast feeding and beyond.30 You may want to advise your patients who desire to use combination oral contraceptives of the increased risk of cardiovascular complications in women older than 35 years of age with a history of smoking, hypertension, or other vascular disease.2,37
Your patient should also know that having gestational diabetes in one pregnancy is a risk factor for the development of this condition in subsequent pregnancies. She needs to understand the benefits of preconceptional counseling and early prenatal care for her future pregnancies.31 It could even be stated that preconceptional counseling for subsequent pregnancies should begin in the postpartum period.37 Since a prepregnancy weight of more than 90 kg is not only a risk factor for gestational diabetes, but for macrosomia as well, it is important to stress the continued importance of diet and exercise for the health of your patient, and the well-being of any future pregnancies.38
| Table 9. Contraindications for Exercise in Pregnancy |
| • Placenta previa |
| • Risk of premature labor |
| • Vaginal bleeding during pregnancy |
| • Pregnancy induced hypertension |
| • Incompetent cervix/cerclage |
| • Intrauterine growth retardation |
| • Malpresentation in the third trimester |
| • Pulmonary disease |
| • Cardiac disease |
| • Thyroid disease |
| • Vascular disease |
| Adapted from Artal R. Exercise: An alternative therapy for gestational diabetes. Phys Sportsmed 1996;24. http:// www.physsportsmed.com/issues/mar_96/artal.htm. |
Management of the Newborn
Infants born from pregnancies complicated by gestational diabetes can have the complications of infants of mothers with pregestational diabetes. They need to have their blood glucose monitored for hypoglycemia. Also, you will want to evaluate their blood count for polycythemia and its accompanying problem of hyperbilirubinemia. These newborns need to be observed closely for respiratory distress. If the neonates are macrosomic (> 4000 g), they need to have their calcium and magnesium levels checked.
Breast feeding should be encouraged; babies should be offered the breast within their first hours of life.25,30 This can be difficult in the setting of cesarian section, separation from the mother for frequent examination and testing, as well as possible dietary supplementation for hypoglycemia.30 Antenatal breast feeding education, support, and counseling should help your patients get over this period of initial discouragement.30
Conclusion
Gestational diabetes is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy. It has serious perinatal and maternal consequences and multiple risk factors. Universal screening for gestational diabetes mellitus with a 50 gm glucose challenge test (or 1-hour glucola) is recommended for all pregnant women between 24-28 weeks gestation. A result greater than or equal to 140 is abnormal. Patients with abnormal results should have a three-hour GTT performed. If any two values are abnormal, the diagnosis of gestational diabetes is made.
Management of gestational diabetes is best accomplished using a team approach. Diet therapy is the mainstay of treatment. Ideally, the blood sugar should be checked at least four times daily to monitor treatment goals. The fasting blood sugar should not exceed 95mg/dL and the two-hour postprandial blood sugar should not exceed 120 mg/dL. Insulin therapy should be instituted in a timely manner for patients who are not controlled with diet and/or exercise.
| Table 10. Treatment Goals for Gestational Diabetes Mellitus | ||
| Time | Blood Sugar1 | Blood Sugar1 |
| Fasting | 95 mg/dL | < 5.3 mmol/L |
| 1 hr PP2 | 140 mg/dL | < 7.8 mmol/L |
| 2 hr PP | 120 mg/dL | < 6.7 mmol/L |
| 1Serum | ||
| 2PP = Postprandial | ||
References
1. Bevier WC, et al. Pancreatic disorders of pregnancy. Diagnosis, management, and outcome of gestational diabetes. Endocrinol Metab Clin North Am 1995;24(1):103-138.
2. Boden G. Fuel metabolism in pregnancy and in gestational diabetes mellitus. Obstet Gynecol Clin North Am 1996;23(1):1-10.
3. Coustan DR. Screening and testing for gestational diabetes mellitus. Obstet Gynecol Clin North Am 1996;23(1):125-136.
4. Coustan DR, Carpenter MW. The diagnosis of gestational diabetes. Diabetes Care 1998;21(S2):B5-8.
5. Kjos SL, et al. Hormonal choices after gestational diabetes. Subsequent pregnancy, contraception, and hormone replacement. Diabetes Care 1998;21(S2):B50-B57.
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Physician CME Questions
15. In the United States, screening for gestational diabetics is recommended for:
a. all pregnant patients within 24-28 weeks of gestation.
b. pregnant patients with risk factors (such as age > 30) only.
c. pregnant patients with a 75 gm, two-hour glucose test.
d. pregnant patients on the first prenatal visit.
e. all pregnant patients with a 100 gm oral glucose tolerance test.
16. Risk factors for gestational diabetes include all of the following except:
a. maternal age older than 30.
b. ethnicity/race.
c. economic status.
d. history of gestational diabetes.
e. history of macrosomia.
17. Complications for mother and fetus with gestational diabetes commonly include:
a. shoulder dystocia.
b. SGA.
c. fetal alcohol syndrome.
d. placenta previa.
e. post dates pregnancy.
18. Strategies for management of gestational diabetes include:
a. weight loss.
b. use of oral hypoglycemic medication.
c. a good, high-fat diet.
d. a team approach including diet, exercise, and insulin therapy when necessary.
e. weekly HbA1C monitoring.
19. Patients diagnosed as having gestational diabetes should:
a. be monitored weekly with FBS and postprandial blood sugars.
b. perform self blood glucose monitoring at least four times daily.
c. be on a diet with nutrients adequate to support maximal fetal growth.
d. be on a weight loss diet.
e. exercise three times daily.
20. The infant of a mother with gestational diabetes is not at risk for which of the following?
a. Hypocalcemia
b. Macrosomia
c. Polycythemia
d. Hyperglycemia
e. Erb’s Palsy
21. Causes of perinatal morbidity include:
a. polycythemia.
b. hypocalcemia.
c. abnormal APGAR.
d. neonatal hypoglycemia.
e. All of the above
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