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DOI: 10.1177/0145721706294263
Preventing Type 2 Diabetes After Gestational DiabetesFrom the Department of Nursing, Spartanburg Community College, Spartanburg, South Carolina (Ms Case); the School of Nursing (Dr Willoughby) and the Department of Food Science and Human Nutrition (Dr Haley-Zitlin), Clemson University, Clemson, South Carolina; and Mountain View Family Practice, Greer, South Carolina (Dr Maybee). Correspondence to Jayne Case, MS, RN, Spartanburg Community College, Department of Nursing, PO Box 4386, Spartanburg, SC 29305 (casej{at}stcsc.edu).
Purpose The purposes of this article are to examine the epidemiology of gestational diabetes mellitus (GDM) and subsequent type 2 diabetes, identify risk factors for the development of GDM and subsequent type 2 diabetes, discuss protocols for postpartum screening, and recommend evidence-based interventions to delay or prevent type 2 diabetes after GDM. Methods A review of the research literature from 1995 to 2005 concerning gestational diabetes was done using MEDLINE, CINAHL, National Institutes of Health, and American Diabetes Association internet resources. The criteria set for selection included the following: the research explored risk factors for and epidemiology of gestational diabetes, the relationship of gestational diabetes and the subsequent development of type 2 diabetes, and/or the prevention of type 2 diabetes after GDM. Results Women with pregnancies complicated by GDM are at increased risk for subsequent development of type 2 diabetes. Research suggests that modification of lifestyle-based risk factors including obesity, poor nutrition, and lack of exercise can delay or prevent the onset of type 2 diabetes in these women. However, there is evidence that recommended postpartum screening protocols for women with GDM are not being followed; hence, those women at high risk for type 2 diabetes are not identified, and no intervention is undertaken to reduce their risks. Conclusions Diabetes educators must play an integral role in increasing awareness of the need for postpartum screening andintervention for women with gestational diabetes. Only with early identification and intensive intervention can the devastating toll of diabetes be averted for many of these women.
Gestational diabetes mellitus (GDM), which occurs in about 4% of pregnancies, is defined as any degree of glucose intolerance with onset or first recognition during pregnancy.1 Insulin resistance, which prevents insulin from exerting its full effect on glucose metabolism, plays a role in the development of GDM. Although some degree of insulin resistance occurs during a normal pregnancy as a result of hormonal release by the placenta, in susceptible women, this physiologic process leads to gestational diabetes mellitus.2 Research has identified a strong correlation between the incidence of GDM and subsequent development of type 2 diabetes.2,3 In addition to the risk for later development of type 2 diabetes, women diagnosed with GDM early in their pregnancies are also at higher risk for obstetric complications and recurrent GDM in future pregnancies.3 As the prevalence of type 2 diabetes increases worldwide, more women are developing diabetes in their childbearing years. The incidence of GDM doubled between the years 1994 and 2002.4,5 The goals of this article are to examine the epidemiology of GDM, identify risk factors for GDM and subsequent type 2 diabetes, discuss protocols for followup for GDM, and recommend interventions that may help decrease the rate of type 2 diabetes after GDM.
Along with obesity, hypertension, sedentary lifestyle, family history, and ethnic origin, GDM is recognized as a significant risk factor for type 2 diabetes.5,6 In a systematic review of research conducted between 1965 and 2001, Kim et al7 identified a strong link between GDM and type 2 diabetes, with the reported incidence of type 2 diabetes ranging from 2.6% to greater than 70% in studies that examined women 6 weeks to 28 years postpartum. After adjusting for differences in diagnostic criteria, initial population selection and follow-up, and retention rates, the authors concluded that women appear to progress from GDM to type 2 diabetes at similar rates, with the highest incidence occurring in the first 5 years after delivery and leveling out after 10 years. Using a case-control design, Aberg et al8 investigated which factors of GDM predict the development of impaired glucose tolerance or diabetes 1 year postpartum. They compared the results of 75-g oral glucose tolerance tests (OGTT) for 60 women with no history of GDM to those of 229 women with a history of GDM (defined as a 2-hour blood glucose level of at least 162 mg/dL [8.9 mmol/L]), 1 year postpartum. Of the GDM women, 31% had abnormal glucose tolerance, while only 1 woman from the control group had an abnormal OGTT. Using linear logistic multiple regression analysis, the authors concluded that maternal age greater than 40 years, high OGTT 2-hour values during pregnancy, and insulin treatment during pregnancy were predictors of impaired glucose tolerance in women 1 year postpartum following GDM. A retrospective cohort study by Lauenborg et al9 investigated the risk factors for and long-term incidence of diabetes among 2 cohorts of women with previous diet-treated GDM. Insulin-treated women were excluded to obtain a more consistent population. The first group delivered between 1978 and 1985 and was examined about 1990 (old cohort, n = 241). The second group delivered between 1987 and 1996 (new cohort, n = 512) and was examined between 2000 and 2002. Both groups were diagnosed using a 2-hour, 75-g OGTT or an intravenous glucagon test. A total of 481 (63.9%) of the women were examined at the median time frame of 9.8 years (interquartile range, 6.4-17.2 years) following pregnancy, and 40 (27%) of them were found to have impaired glucose tolerance (IGT) or impaired fasting glucose. When examined by cohort, women who delivered between 1987 and 1996 had a 40.9% incidence of type 2 diabetes compared to 18.3% in the older cohort. Women in the new cohort had significantly higher prepregnancy body mass indexes (BMIs) than women in the older cohort did. High prepregnancy BMI and postpartum IGT were identified by multiple logistic regression to be independent predictors of type 2 diabetes after GDM. These findings provide a solid basis for postpartum screening protocols recommended by the American Diabetes Association (ADA) and the World Health Organization (WHO).
The ADA and the WHO differ as to the preferred diagnostic test for diabetes. The ADA recommends the use of plasma glucose levels and does not recommend the OGTT for routine clinical use.10 The WHO recommends a 75-g OGTT as its standard for diagnosis.11 This test, however, is more expensive and time-consuming than plasma glucose testing, and in 1 study, almost 20% of postpartum women with GDM failed to carry out the recommended OGTT.4 Because of the concern that the different guidelines may create confusion and make comparison of rates of GDM difficult, investigators have conducted research to compare OGTT and fasting plasma glucose (FPG) testing.4,12 In an effort to determine whether an FPG at 6 weeks postpartum can identify women with an abnormal OGTT, Holt et al4 conducted a retrospective study of 152 women with GDM. They found that the FPG was significantly correlated with the 2-hour OGTT level (r = 0.62, P < .0001) and concluded that the fasting glucose test is a good indicator of which women need follow-up with an OGTT.4 The FPG test was also compared to the OGTT in a 5-year study of 549 women with recent histories of GDM by Agarwal et al.12 They found that results of the 2 tests were similar with regard to the diagnosis of the prevalence of diabetes (8.2% vs 6.6%) but varied significantly on the rates of impaired glucose metabolism. The OGGT showed a 15.5% prevalence of IGT compared to a 9.3% prevalence of impaired fasting glucose. Follow-up studies of women with GDM are necessary to establish the most efficient and cost-effective approach to postpartum screening for type 2 diabetes. Regardless of the screening method used, there is evidence that many women with GDM are not being appropriately screened for type 2 diabetes in their postpartum period.13,14 The ADA Expert Committee on the Diagnosis and Classification of Diabetes Mellitus recommends glucose testing 6 to 8 weeks after delivery for women with GDM and, if normal, at a minimum of 3-year intervals.10 In a retrospective, observational review of the records of 158 women with GDM, Dinh et al13 found that while 96% of the women returned for their 6-week postpartum office visit, postpartum glucose testing was offered to only 60.5%, and only 34% actually underwent diabetes testing. In a Canadian study to examine the impact of the 1998 Canadian Diabetes Association guidelines recommending the use of the OGTT to screen for type 2 diabetes after GDM, the authors found that both before and after the guidelines, none of the women in their study had had an OGGT and, furthermore, that only 52% (69 of 131) of the women preguideline and 42% (52 of 123) postguideline had any type of screening blood work recorded.14 Identifying those women who develop or are at high risk for developing type 2 diabetes after GDM is only the first step in the arduous task of managing this potentially devastating health problem. After diagnosis, the challenge of making the lifestyle changes needed to prevent or manage the disease remains.
Lifestyle modification that promotes weight loss is key to preventing or delaying type 2 diabetes in women with histories of GDM.15-23 Sustained change, however, is difficult to achieve. In one study, 121 Danish women with GDM were surveyed 11 to 42 months after their pregnancies.19 Despite having been instructed concerning needed lifestyle changes, only 18% of the women with a BMI greater than 25 kg/m2 had lost weight and more than 33% had gained weight. Furthermore, 16% were diagnosed with diabetes and 18% with IGT at follow-up.19 The Stockholm Pregnancy and Women's Nutrition study, a 15-year retrospective case-control study, monitored the weight and associated lifestyle habits of 28 women diagnosed with GDM and 52 control women without GDM who delivered in 1984 and 1985. At 15-year follow-up, 35% of the women with histories of GDM were found to have type 2 diabetes compared to 0% in the control group.20 Among those women with histories of GDM, the group who developed type 2 diabetes had a significantly higher mean BMI (27.4 kg/m2) than the women who had not developed diabetes (24.6 kg/m2). Those women with type 2 diabetes had gained a mean 15.1 kg since their first pregnancy. These researchers also found that women with a history of GDM were unlikely to contact their primary clinicians until they actually developed signs of type 2 diabetes mellitus. These studies underscore the importance of working with women who have histories of GDM to make healthful lifestyle changes. Preventative strategies (Figure 1) should incorporate clinical interventions beginning with the 6-week postpartum screening (plasma glucose, BMI, cholesterol, and lipoprotein levels). Considering the potential risks for metabolic syndrome, the diabetes educator should assess cholesterol and lipoprotein levels during the initial postpartum screening to establish a baseline and aid in a treatment plan for diet therapy. After establishing that the patient's risk factors for type 2 diabetes are significant, the diabetes educator should assess the patient's dietary habits and physical activity behaviors and begin patient education that addresses behaviors that place the patient at risk for type 2 diabetes and other comorbidities. Once the patient understands her risk and is willing to modify her behaviors, the diabetes educator and patient must work together to form a partnership, deciding on mutual goals that will reduce her risk for type 2 diabetes (Figure 2). It may be beneficial for the diabetes educator to incorporate a teaching record (Table 1) into the plan of care to aid in identifying patient areas that need additional follow-up and reinforcement. Behavioral changes that are aimed at decreasing the patient's risks for type 2 diabetes should include diet therapy and physical activity.
Following delivery, women with GDM should be reclassified as normoglycemic, having IFG or IGT, or diabetic. At the initial 6-week postpartum screening, a patient should undergo an FPG or a 75-g 2-hour OGTT. Using FPG, values less than 100 mg/dL (5.6 mmol/L) would be classified as normal, values between 100 and 125 mg/dL (5.6-6.9 mmol/L) as IFG, and values of 126 mg/dL (7 mmol/L) or greater as diabetes. If using the 75-g 2-hour OGTT, a normal glucose value is less than 140 mg/dL (7.7 mmol/L), with IGT values between 141 and 199 mg/dL (7.8-11 mmol/L), and diabetes is diagnosed with glucose values greater than or equal to 200 mg/dL (11.1 mmol/L).10 Postpartum screenings should also include BMI. Weight and height should be measured with the patient wearing only undergarments and no shoes. Patients with BMIs of 25 kg/m2 or greater are considered overweight, and those with BMIs of 30 kg/m2 or greater are considered obese. Women who fall into the overweight or obese categories and women who have high blood pressure should have cholesterol and lipoprotein levels measured to address the following comorbidities, which are components of metabolic syndrome:
Once risk has been established, a behavioral assessment can help the woman and the diabetes educator identify behaviors that contribute to that risk. A behavior change plan can then be collaboratively developed, stressing the potential for such change to reduce the patient's risks for type 2 diabetes and its comorbidities.
Diabetes educators should assess all behaviors that influence a woman's health to help her make appropriate modifications to achieve positive outcomes. Behavior modification strategies that foster changes in diet and physical activity play a significant role in weight loss. These changes may be achieved on an individual basis or in group settings.
Components of the health belief model may be useful in assessing and changing behaviors that contribute to the development of type 2 diabetes after GDM.24-26 These components include the following:
By considering the patient's beliefs and perceptions about diabetes and lifestyle change, the patient and diabetes educator can determine how best to achieve the goals they mutually establish (Table 2).
The diabetes educator can further assist patients to learn to self-monitor and adjust their behaviors.21-23 Changing habitual behaviors requires heightened self-awareness. One study found that the more self-monitoring records patients kept per week, the more weight they lost.22
Weight loss is critical to delaying or preventing the onset of type 2 diabetes in women with previous GDM; however, attainable goals should be set to avoid a sense of futility and failure.17 Research shows that even in the absence of significant weight loss, health benefits accrue from moderate exercise and improved nutrition. Furthermore, a very moderate weight loss of 5% to 10% of the patient's body weight significantly affects the risk for diabetes and metabolic syndrome. Therefore, when setting goals, the diabetes educator should encourage a gradual approach to achieve sustainable long-term lifestyle change. The goal of dietary therapy is to help the woman decrease caloric intake while maintaining adequate nutrition. Current recommendations are to create an energy deficit of 500 to 1000 kcal/d to achieve a slow but progressive weight loss of 0.5 to 1 kg per week.27,28 Self-monitoring of caloric intake is particularly important, as obese people tend to underestimate their intake by 30% to 50%.22 The use of multiple methods of self-monitoring of intake can help the woman incorporate the meal plan into her lifestyle. First, the diabetes educator should teach the patient how to count the calories based on the types of nutrients consumed and the serving size (Table 3). Awareness of portion size is vital to weight loss. The ADA recommends teaching patients to examine their plates before eating to proportion their foods as follows: one fourth grains or starchy foods, one fourth protein, and one half nonstarchy vegetables.28 The patient may then also add an 8-oz glass of nonfat milk or a piece of fresh fruit. Other important dietary skills for women with a history of GDM include the ability to read and interpret labels and to choose appropriate foods when eating out. The ADA provides many tips and techniques that may be useful in developing a dietary plan. Skill development requires practice, and this is true for women learning diet management skills. The opportunity to select appropriate foods, measure portion size, read labels, and maintain records of intake can contribute to the adoption of these behaviors. In addition to self-monitoring, other helpful techniques include stimulus control, slower eating habits, cognitive restructuring, problem solving, and relapse prevention.24
Increasing physical activity levels not only contributes to weight loss but can also reduce blood glucose levels. Advice from the health care provider can influence at-risk patients to increase their activity levels; however, patient involvement in the planning of a physical activity program is crucial to its success.29 Initiation of an exercise program should follow an extensive history and physical examination. If there are no contraindications to exercise, the plan should be initiated by beginning a progressive exercise program that will start the patient out slowly and increase endurance gradually. The ADA offers educational materials and guidelines to assist with the initiation of a physical activity program.17 Women who have not recently been physically active should start with a 5- to 10-minute workout daily with the goal of gradually increasing activity and endurance to 30 minutes at least 5 days per week. Examples of effective aerobic exercise include brisk walking, dancing, swimming, skating, playing tennis, and riding stationary bikes.17 Diabetes educators should have written material available showing calorie expenditures involved for different exercises (Table 4).
Strength training enhances weight loss and is important for women to build strong bones and muscles. Light weights, elastic bands, or plastic tubes are effective in achieving improved strength and muscle tone that aids in metabolism of glucose.27 Flexibility exercises that involve stretching improve joint function and reduce the risks of injury to bones and muscles. Gentle stretching of 5 to 10 minutes per day, before and after exercise, is vital in improving the body's benefit from aerobic workouts. Three months into the weight loss program, the patient should be weighed, the BMI calculated, and progress evaluated. If the patient has achieved some degree of weight reduction, she should return 3 months later for additional assessments. If the patient has achieved a 10% weight reduction in 6 months to 1 year, the weight reduction should be considered to be good progress. If weight loss has not occurred, the diabetes educator and patient should reevaluate the diet and exercise programs to attempt to determine what modifications are needed.
Approximately 200 000 pregnancies are complicated by GDM annually.1 As studies show, women with GDM have an increased risk for type 2 diabetes and its comorbidities. Preventing diabetes in these women is an enormous feat for both patients and diabetes educators. Although additional research is necessary to validate many of the current findings, there is substantial evidence to show that type 2 diabetes can be delayed or prevented with lifestyle modifications. One of the most crucial clinical interventions, as seen in the health belief model, is to empower women with histories of GDM to take more control over modifying those behaviors that increase their risk for type 2 diabetes. Current research suggests that this goal can be best accomplished by implementing education and support that encourage long-term lifestyle changes that lead to weight loss.
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Abstract
Epidemiology
