Gestational Diabetes During and After Pregnancy

20. Risk for Maternal Postpartum Diabetes

Catherine Kim 

(1)

Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA

Catherine Kim

Email: cathkim@med.umich.edu

Abstract

For over half a century, gestational diabetes mellitus (GDM) has been recognized as a risk factor for maternal diabetes after delivery or postpartum. GDM confers a 7-fold risk for future diabetes, independent of other significant risk factors such as weight, visceral adiposity, and physical activity. Up to a third of women with diabetes may have been affected by prior GDM. However, postpartum studies of GDM women are relatively few compared to prenatal and peripartum examinations. This chapter reviews methodological issues and risk factors affecting postpartum maternal diabetes risk estimates. The chapter also presents evidence regarding the risk for future cardiovascular disease among women with a GDM history. In doing, so, the chapter underlines the need for, and lack of: uniform diagnostic criteria and screening strategies for the index diagnosis of GDM as well as for postpartum glucose intolerance; quality improvement initiatives to improve postpartum glucose screening; and diabetes prevention interventions in this population. Perhaps most importantly, this chapter underlines the significance of GDM upon postpartum maternal glucose tolerance outside of pregnancy.

20.1 Introduction

Gestational diabetes mellitus (GDM) confers a sevenfold risk for future diabetes, independent of other significant risk factors such as weight, visceral adiposity, and physical activity.12 Up to a third of women with diabetes may have been affected by prior GDM.3 This chapter reviews the factors affecting postpartum diabetes risk in women with a GDM history. Methodological issues include varying diagnostic criteria for GDM and postpartum diabetes. The discussion of risk factors begins with traditional risk factors for glucose tolerance as they apply to women with a GDM history, and further describes several risk factors for postpartum maternal diabetes unique to GDM women. These latter factors arise from the index diagnosis of GDM, and include glucose levels obtained from prenatal diagnostic testing, earlier onset of glucose intolerance during pregnancy, elevated glucose levels during pregnancy, and the need for hypoglycemic medication during pregnancy. The chapter concludes with studies that examine GDM women’s future cardiovascular disease risk.

20.2 Factors Affecting Estimates of Postpartum Diabetes Risk: Diagnostic Criteria

In a 1991 review, John B. O’Sullivan observed: “Although the variability in diabetes incidence rates is wide, there is broad general agreement on the predictive nature of gestational blood glucose levels,”4 a statement that still holds. His report, including his own landmark studies of Boston City Hospital women with GDM, noted postpartum diabetes cumulative incidences ranging from 5 to 87%.4 He further noted that differing criteria for the index GDM diagnosis and postpartum diabetes diagnosis contributed unnecessary variation in risk estimates. In other words, apart from diabetes risk factors themselves, methodological issues affect estimates of postpartum diabetes risk. Diagnostic criteria for the index diagnosis of GDM define the population and therefore the denominator of postpartum diabetes risk estimates. Background screening rates also affect postpartum diabetes risk estimates by reducing the number of high-risk women with GDM who had undetected glucose tolerance preceding pregnancy. Diagnostic criteria for postpartum diabetes define the outcome. Finally, cohort retention, particularly if the cohort loses high-risk women, also influences postpartum diabetes risk estimates. The following section reviews each of these issues.

20.2.1 Diagnostic Criteria for GDM

As discussed in chapter 3, the criteria for the index diagnosis of GDM vary significantly across medical organizations and centers. In general, the lower the glucose cut-offs, the broader the range of risk in the population subsequently diagnosed with GDM. Identification of a greater proportion of pregnant women with GDM necessarily leads to a greater denominator, and a decreased proportion subsequently identified with postpartum glucose intolerance. Conversely, more specific, but less sensitive GDM criteria lead to fewer women identified with GDM. However, a greater proportion of these women are subsequently identified as having postpartum glucose intolerance.

Ferrara et al demonstrated this in their study, in which two sets of GDM diagnostic criteria were applied to women who underwent glucose tolerance testing during pregnancy.5 Of these women, 3.2% had GDM by National Diabetes Data Group criteria. Of the same women, 4.8% had GDM by Carpenter and Coustan criteria, which uses lower glucose cut-offs. With the lower cut-offs, the prevalence of GDM increased by approximately 50%. However, the additional populations identified tended to be low risk; relative increments were greatest in low-risk age and ethnic groups, specifically women aged <25 years (70%) and in whites (58%). Thus, although the denominator, women with GDM, increased, the additional women identified were at similar or lower risk when compared with the original National Diabetes Data Group cohort.

20.2.2 Background Screening for Diabetes

Diabetes screening is not routine in non-pregnant women of reproductive age. The American Diabetes Association (ADA) recommends screening for diabetes beginning at age 45 years in the absence of risk factors,6 and other medical organizations such as the United States Preventive Services Task Force (USPSTF)7 and the World Health Organization (WHO)8 do not categorically recommend screening unless other risk factors for diabetes or cardiovascular disease are present.

No studies examine how background detection rates might affect postpartum diabetes risk estimates. More frequent background diabetes screening in non-pregnant women prior to conception might lead to greater identification of women with preconception diabetes, and decrease the number of women identified with GDM.9 However, since background screening rates occur in the setting of changing risk factors rates, such as obesity and multiparity, it is difficult to isolate the impact of background screening.

20.2.3 Diagnostic Criteria for Postpartum Glucose Intolerance

Criteria for postpartum glucose intolerance vary between medical organizations. The primary debate is whether screening should consist of performance of a postpartum fasting glucose alone vs. a 75-g oral glucose tolerance test (OGTT). The 2007 Fifth International Workshop-Conference on GDM recommends that a 75-g OGTT be performed ≥6 weeks postpartum to screen for maternal glucose intolerance.10The Australasian Diabetes in Pregnancy Society also endorses the 75-g OGTT. The 2003 Canadian Diabetes Association guidelines prefer the 75-g OGTT, but state that the fasting glucose is acceptable.11 As of 2007, the United Kingdom-based National Institute for Health and Clinical Excellence (NICE) recommends a postpartum fasting glucose only, specifically without the OGTT.12 In 2009, the American College of Obstetricians and Gynecologists stated that screening should be performed and notes that the OGTT demonstrates greater sensitivity than the fasting glucose, but that fasting glucose is acceptable,13 a contrast with its previous agnostic recommendations regarding screening.

The diabetes screening guidelines of other medical organizations adopt the guidelines for general at-risk populations. The 1999/2006 WHO guidelines recommend a 75-g OGTT.8,14 The 1997/2003 ADA guidelines recommend a fasting glucose in general practice, although the guidelines recognize the OGTT as a valid diagnostic method.6,15 The USPSTF does not make specific recommendations for postpartum screening among women with GDM, perhaps reflecting its lack of support for GDM screening during pregnancy.16

While organizations differ as to whether or not to obtain the 2-h glucose, the cut-offs for diabetes are similar across groups: fasting glucose of 7.0 mmol/L or 126 mg/dL and, if obtained, a 2-h glucose of 11.1 mmol/L or 200 mg/dL after a 75-g challenge. The fasting glucose value of 126 mg/dL was chosen due to its threshold association with retinopathy.17 The 2-h criterion of 200 mg/dL corresponded with both all-cause and cardiovascular disease mortality, as well as providing roughly the same risk as a fasting glucose of 126 mg/dL.17

The glucose test results may also be used to determine the presence of impaired glucose regulation (IGR).14 IGR consists of impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). The ADA defines IFG as a fasting glucose level ≥100 mg/dL or 5.6 mmol/L15 and the WHO defines IFG as a fasting glucose level ≥110 mg/dL or 6.1 mmol/L.8 The ADA defines IGT as a 2-h glucose 140–199 mg/dL or 7.8–11.0 mmol/L, as does the WHO. The IFG cut-off was chosen based on review of receiver operator curves (ROCs) for diabetes prediction and the disagreement between ADA and WHO was based on whether ROCs should be the basis for cut-offs.8,15 The IGT cut-off was initially chosen more arbitrarily, although the 2-h glucose does correspond with cardiovascular mortality and future diabetes.8,15 In addition, Diabetes Prevention Program participants were required to have IGT and did respond to diabetes prevention interventions.17,18

More sensitive criteria result in greater estimates of postpartum diabetes risk. The OGTT is more sensitive than the fasting glucose alone because the fasting glucose and 2-h glucose capture overlapping, but not identical populations. Fasting glucose may reflect hepatic insulin resistance and early-phase insulin secretion, whereas glucose levels obtained after a glucose challenge may reflect peripheral insulin resistance and later-phase insulin secretion.19 Women may have defects in either.19 In the National Health and Examination Survey III, 44% of adults ≥40 years with IGR met both the 2-h and fasting criteria.20 Fourteen percent met the fasting criteria but not the 2-h criteria, and 41% met the 2-h criteria alone.20 In the European DECODE study, only 28% of IGR participants met both criteria, and 31% met the 2-h criteria only.21

The greater sensitivity of the OGTT is complicated by the greater variability in the 2-h glucose level compared with the fasting glucose.22 The day-to-day intraindividual coefficients of variation range from 6.4 to 11.4% for fasting glucose and 14.3 to 16.7% for the 2-h glucose.22,23 In addition, the OGTT has greater initial cost and inconvenience, drawbacks cited by the ADA and NICE.6,12,15 Finally, there is a lack of consensus regarding utility of intervening for pre-diabetes states,7 for cardiovascular disease prevention,17 and for mortality prevention.17

The debate over which diabetes screening test is optimal extends to postpartum women with a GDM history. Among these women, as in the general population, the fasting glucose and 2-h glucose identify distinct groups. In several postpartum GDM cohorts, approximately 5–10% of women have IFG only, about 10–15% have IGT only, and 10–15% have both.2427 Other studies have also found limited sensitivity of fasting glucose for IGR and DM in postpartum GDM women,28,29 particularly for IGR.29 To our knowledge, no studies examine the diagnostic properties of the HbA1c in the postpartum population. Therefore, despite the convenience of the HbA1c assay, its value for diagnosis is still unknown for postpartum GDM women.

Several issues unique to women with recent GDM could potentially influence choice of screening test in this population. First, women with recent GDM might benefit from more sensitive screening strategies, since diabetes poses risk to future pregnancies. Specifically, this risk includes congenital anomalies of cardiac malformations, neural tube defects, and limb dysgenesis. All are strongly associated with HbA1c before conception.30 Second, women with GDM are, on average, approximately 10–20 years younger than other populations diagnosed with IGR and diabetes.9,31 Women with GDM who develop diabetes face relatively prolonged dysglycemia, which could potentially place them at higher risk for diabetes complications than the general population. Earlier identification could lead to reduction of complications. In the Diabetes Control and Complications Trial and its follow-up, intensive treatment reduced microvascular complications, with effects persisting after discontinuation of the trial.32 In statistical models, the postpartum OGTT is generally more advantageous among women with recent GDM if diabetes identification is the endpoint.33 Finally, earlier identification of IGR could lead to preventive efforts.

20.2.4 Ascertainment Bias: Performance of Postpartum Screening and Cohort Retention

Regardless of the screening criteria used, multiple reports demonstrate that performance of postpartum screening for those with a GDM history has been the exception, rather than the rule.24,26,27,3436While performance of screening has improved over the past decade, almost half of the women with a GDM history do not undergo screening of any kind or undergo screening with tests such as glycosylated hemoglobins.27,37 Before 2010, the latter tests have not been recommended as screening tests due to relatively decreased sensitivity and specificity.17

Reasons why women forego screening are speculative, but include women’s low perception of diabetes risk,38 lack of healthcare provider perception of risk,39, 40 and lack of other steps necessary for screening such as lab slip distribution or test-ordering.39,41 The reasons why women forego screening may also differ between study populations. Russell et al found that screened and unscreened women had similar glucose levels during pregnancy,35 but screened women were more likely to attend the postpartum visit, suggesting that barriers to the postpartum visit also presented barriers to screening. In contrast, Smirnakis et al found that greater than 90% attended a postpartum visit, suggesting that attendance of the postpartum visit was not the major barrier.34

Quality improvement studies on this topic are few. In Texas, Hunt and Conway noted that screening performance improved with nurse case-management,26 including mailed reminders, telephone calls, and home visits. In a Canadian study, where postpartum OGTT costs are not billed to the patient as in most developed countries aside from the United States, mailed reminders increased screening rate.42 Ferrara et al also noted that referral to a nurse case-management program for general GDM management during pregnancy increased screening fourfold after pregnancy (personal communication).

Infrequent postpartum screening leads to missed diagnoses of postpartum glucose intolerance. In addition, low performance of postpartum screening could bias estimates of future diabetes risk if screened women were different than unscreened women. In a systematic review of studies examining conversion to type 2 diabetes, Nicholson et al found that 75% of studies included reported a loss to follow-up greater than 20%.43 In particular, retrospective cohorts including only women who have undergone the postpartum test might misrepresent risk. If women who were not screened were at lower or higher risk than women who were screened, this would overestimate and underestimate diabetes risk estimates, respectively. Indeed, women who are not screened may have greater prevalence of risk factors for diabetes, including elevated glucose levels,2634 prior macrosomia,24 poorer education,27obesity,27 and macrosomia.27

20.3 Factors Affecting Estimates of Postpartum Diabetes Risk: Risk Factors for Maternal Postpartum Diabetes

Methodological issues aside, postpartum diabetes risk estimates also reflect the underlying glucose tolerance of the population. While risk factors for diabetes among women with GDM vs. women in the general population overlap, there are several key differences. Women with a GDM history are distinct from the general population in that they have exhibited glucose intolerance when exposed to the greater metabolic demands of pregnancy. Risk factors that predict diabetes in the general population do not always predict diabetes among women with histories of GDM. Also, information on traditional diabetes risk factors, particularly lifestyle behaviors, is more limited among women with a GDM history than other at-risk populations for diabetes due to lack of study.

Several risk factors unique to GDM women predict postpartum glucose intolerance and arise from the index diagnosis of GDM. Glucose levels obtained from prenatal diagnostic testing reflect underlying maternal glucose intolerance and are associated with postpartum diabetes. Earlier onset of glucose intolerance during pregnancy, elevated glucose levels during pregnancy, and levels that require treatment with hypoglycemic medication are also associated with future maternal diabetes risk.

20.3.1 Measures of Glucose Intolerance During the Index GDM Pregnancy

20.3.1.1 Fifty-Gram Screening Test and Diagnostic OGTT

Glucose intolerance during the index GDM pregnancy, reflected by the glucose values on the 50-g glucose challenge screening test as well as the diagnostic prenatal OGTT, are associated with postpartum hyperglycemia and diabetes.4449 Due to variation in diagnostic testing procedures for GDM, as well as the continuous relationship between glucose values and future risk, no single glucose value consistently identifies women at risk for future diabetes.44

As discussed in the chapters regarding the guidelines for diagnosis of GDM and its prevalence, the 50-g glucose challenge is often, but not always, performed during pregnancy as the baseline screening test for GDM. The glucose value from this screen is independently associated with postpartum hyperglycemia,44 even after adjustment for women’s prenatal OGTT values.49

The glucose values on the diagnostic prenatal OGTT, whether measured as area under the curve or as tertiles for individual values, and whether measured as part of a 75- or 100-g OGTT, predict greater maternal postpartum glucose intolerance.24,4555 As fasting and post-challenge glucose values detect different populations at risk for glucose intolerance in non-pregnant adults, fasting and post-challenge values on the prenatal OGTT are associated with postpartum hyperglycemia to different degrees and in different groups of pregnant women. Women with a greater number of abnormal tests, i.e., elevated fasting or post-challenge values, are at greater risk for diabetes.24 The prenatal glucose area under the curve reflects an average of all of the prenatal OGTT values and reflects any abnormality in glucose metabolism, although the area under the curve does not distinguish between specific defects.

Elevations in any of the glucose values from the prenatal OGTT are associated with greater postpartum diabetes risk, but fasting glucose and 1-h glucose may be more strongly associated with postpartum diabetes than 2- and 3-h values.4453,56

While not commonly used in clinical practice, several measures may more precisely capture specific defects in glucose metabolism.24,44,51,52,55 These measures most commonly involve proxies for insulin secretion and sensitivity rather than direct measures using euglycemic clamp studies.57 Proxies for insulin secretion include insulin and glucose ratios measured after a glucose load58 or C-peptide-to-glucose levels.24 Insulin sensitivity is commonly represented by fasting insulin or by equations incorporating fasting insulin and fasting glucose levels.59 In pregnant women with GDM, both insulin resistance and insulin secretion are independently associated with postpartum diabetes even after adjustment for prenatal OGTT levels.24,51,55

20.3.1.2 Medications During the Index GDM Pregnancy

Treatment required during the index GDM pregnancy may also reflect underlying glucose intolerance. Pregnancies requiring sulfonylureas27 or insulin45,46,4850,6063 may reflect greater glucose intolerance than pregnancies requiring lifestyle management only. Class A2 GDM is GDM requiring insulin therapy because of fasting levels ≥105 mg/dL; this particular category of GDM is associated with postpartum diabetes even after adjustment for the actual fasting glucose level as well as other prenatal OGTT levels.49 Women eventually placed on insulin or a sulfonylurea may still be at higher risk for future diabetes after adjustment for A2 class.27,45,46,60 Treatment status may provide additional predictive value, because treatment may reflect progression of insulin resistance and/or β-cell dysfunction later in the pregnancy, whereas prenatal OGTT levels reflect glucose metabolism at the time of diagnosis. However, treatment may reflect other health-care delivery factors such as greater likelihood of follow-up, compliance with medication, and compliance with a postpartum OGTT.27

20.3.1.3 Gestational Age at the Time of GDM Diagnosis

Testing for GDM generally occurs between 24 and 28 weeks of pregnancy. However, testing may occur earlier if the healthcare provider suspects glucose intolerance. Earlier gestational age at time of diagnosis, indicating earlier onset of glucose intolerance, has been associated with greater risk of postpartum diabetes,4749,52,61,62,64,65 even after consideration of the degree of elevation in glucose levels.4850 This association is driven by pregnancies diagnosed at extremes of gestational age, as this risk was not significantly elevated when women in the middle of the gestational age distribution were included.4749,52,66

20.3.2 Other Risk Factors for Future Diabetes: Adiposity

Anthropometric factors reflect adiposity, a step in the causal pathway of insulin resistance.67 While adiposity is generally associated with future glucose intolerance, different anthropometric measures reflect different types of adiposity, which in turn are associated with future diabetes to differing degrees. Greater central or visceral adiposity, as reflected by waist circumference and waist-hip ratio, has stronger risk for GDM than subcutaneous adiposity or traditional measures of body mass.68 Central adiposity has also been associated with defects in both insulin secretion and sensitivity among women with a GDM history.69

The association of future diabetes with preconception24,47,5052,61,62 and prenatal adiposity measures45,53,60,61,70 tends to be less robust than postpartum assessments,46,54,62,63,7174 which are more proximal to diabetes onset. Obviously, adiposity measurements across the three periods still correlate highly. Preconception and prenatal associations with diabetes did not always remain robust in multivariate analyses including prenatal OGTT glucose levels.48,51537577 This suggests that prenatal adiposity effects upon metabolism were reflected by prenatal OGTT glucose.

20.3.3 Other Risk Factors for Future Diabetes: Sociodemographic Factors

The association between traditional sociodemographic risk factors and postpartum maternal diabetes is not as strong in women with a GDM history as in the general population. This may reflect that women with GDM are already at high-risk, and the factors that predispose them to GDM have minimal additional predictive value for postpartum maternal diabetes.2 With a few exceptions,62,63,74 maternal age at the time of GDM diagnosis has not been associated with future maternal diabetes,45,47,48,5153,60,61,65,66,71,75,78 although older age predicts glucose intolerance in the general population.79 This may be because maternal age already predicts the onset of GDM itself,80 as noted in chapter 5. The lack of association may also be due to the narrow range in maternal age in GDM women, since maternal age generally does not exceed 50 years.

Non-white race is associated with greater diabetes risk in the general population of women, even after adjustment for body mass.81 Among women with GDM, within-study comparisons of race for future diabetes incidence have sometimes found greater diabetes risk among non-white women,82,83 but this finding has not been consistent across studies.66 This may reflect the fact that higher-risk racial-ethnic groups, such as Latinas and Asians, have already developed GDM.84 Alternatively, it may reflect that these comparisons are relatively uncommon, due to the homogeneity of the populations within most studies. Between-study comparisons suggest a lower incidence of diabetes among non-Hispanic white women85 compared with women of non-white race/ethnicity,86 but definitive conclusions are hard to draw due to selection criteria that differ across studies.

Family history of type 2 diabetes45,47,52,53,71,75,76,87 has generally not been associated with maternal postpartum diabetes in GDM women, perhaps for the same reasons that age and race have not. While parity53,60,73,75,78,87 has not been associated with postpartum diabetes in GDM women in most studies, grand multiparity,63 an additional pregnancy after the index pregnancy,54 and number of GDM pregnancies are associated with postpartum diabetes risk.46,49

20.3.4 Other Risk Factors for Future Diabetes: Lifestyle Behaviors

Surprisingly little information exists regarding behaviors and future diabetes risk among women with a GDM history. chapter 5 presents evidence that physical activity levels88 and dietary habits85 are risk factors for the index diagnosis of GDM, but reports do not comment upon these factors for postpartum maternal diabetes. Chapters 21 and 22, respectively, discuss the diabetes risk associated with various hormonal contraceptives and breastfeeding.

20.3.5 Other Risk Factors for Diabetes: Non-Glucose Factors

Among the general population of women, inflammatory and endothelial factors are associated with glucose intolerance.89,90 Among women with a GDM history, studies are relatively few. The role of inflammatory markers is discussed in more detail in chapter 10.

Autoantibodies, including antibodies to islet cells, insulin, the tyrosine phosphatases, and glutamic acid decarboxylase, are associated with the development of type 1 diabetes in the general population and among women with a GDM history.91 Fuchtenbusch et al found that the degree of diabetes risk was associated with the number of antibodies present.92 In a 2007 report, de Leiva et al reviewed 17 studies examining autoantibody status and development of diabetes.91 Autoantibodies were generally associated with diabetes development except in four smaller studies. Of note, adjustment for other factors, particularly glucose levels, was not performed in most studies. The prevalence of antibodies was examined in primarily non-Hispanic white populations, which have a relatively decreased prevalence of type 2 diabetes as compared with type 1 diabetes. Therefore, the additional predictive value of autoantibodies is not yet established.

20.4 Cardiovascular Risk

Among the general population of women, blood pressure levels, low high-density lipoprotein cholesterol (HDL), and high triglycerides are associated with type 2 diabetes.93 Among women with a GDM history, blood pressure levels24,71,72,82,94 and HDL and triglyceride levels24,71,72,82,94,95 have also been associated with diabetes and IGR. Levels of blood pressure and lipids were usually within normal range and related to glucose continuously, without a threshold effect, making it difficult to use these factors for diabetes risk stratification. In a cross-sectional analysis, Kim et al found that women with a GDM history who do not have diabetes may not have increased risk of other cardiovascular risk factor abnormalities.96 As of publication, we are unaware of any prospective studies that have examined the sequence of cardiovascular risk factor evolution, including glucose, blood pressure, lipids, and inflammatory and endothelial markers, among women with a GDM history.

As GDM is associated with elevations in cardiovascular risk factors, it is not surprising that GDM is associated with vascular dysfunction and future cardiovascular disease. Heitritter et al found that women with a GDM history had greater vascular resistance, lower stroke volume, and lower cardiac output than women without a GDM history.97 Bo et al found that women with a GDM history also had increased intimal medial thickness compared to women without a history.98 In a cross-sectional study, Carr et al found that women with a GDM history were more likely to have metabolic syndrome and to experience cardiovascular events than women without a GDM history, and moreover, that these cardiovascular events occurred at a younger age.99 Shah et al found that this increased risk of cardiovascular events, although low, seemed to be primarily attributable to their greater risk of diabetes.100 They noted that the evolution of cardiovascular risk factor abnormalities and diabetes was not studied, and thus, diabetes did not necessarily precede the diagnosis of other cardiovascular risk factors.100

20.5 Conclusions and Research Needed

GDM and its attendant controversies in diagnosis and follow-up highlight the importance of examining pregnancy diseases for their impact on postpartum maternal health. While medical care has traditionally treated prenatal and postpartum care as separate, glucose tolerance does not respect this boundary. Postpartum studies of GDM women are relatively few compared to prenatal and peripartum examinations. Limiting factors include women’s low risk perception for future diabetes38 in conjunction with their provider’s low risk perception,39,40 the socioeconomically disadvantaged profile of GDM women in the United States,101 and lack of continuity of care between pregnancy healthcare providers and postpartum providers. Greater attention needs to be devoted to improving postpartum screening and consensus on screening guidelines.

Currently, no large prospective cohort studies of GDM and non-GDM women exist. Such studies would establish diabetes conversion rates and incidence of other chronic disease. Such studies would be useful in establishing postpartum screening criteria for GDM women by comparing morbidities associated with fasting value, the 2-hour value, HbA1c, and the variation in each of these tests.

Most importantly, interventions for women with recent GDM need to be developed, in order to improve postpartum screening and maternal chronic disease prevention. The value of intervention for IGR women or diabetic women with a GDM history is assumed to be similar to the general population, but has not been independently established. Such interventions also need to be evaluated for their long-term effects on offspring. Successful interventions would leverage the tight interrelationship between maternal and child health during the unique condition of pregnancy, and in doing so, avert disease in an efficient and cost-effective manner.

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