Do the current standards for glucose tolerance testing in pregnancy represent a valid conversion of O'Sullivan's original criteria?

Serum concentration of angiogenic (CXCL1, CXCL12) and angiostasis (CXCL9, CXCL10) CXC chemokines are differentially altered in normal and gestational diabetes mellitus associated pregnancies

BACKGROUND

The present study was aimed and designed to determine the serum levels of CXCL1 and CXCL12 as angiogenesis along with CXCL9 and CXCL10 as angiostasis, chemokines in, Gestational diabetes mellitus mothers (GDMM) and normal pregnancy mothers (NPM) and neonates who delivered by them.

METHODS

We have recruited 63 pregnant GDMM and 63 normal pregnant mothers at the third trimester of pregnancy to this cross-sectional study. Cord blood specimens were obtained from neonates who were delivered from GDMM and NPM. The serum and cord blood levels of chemokines were measured by ELISA in studied groups. Data were analyzed by chi-square and student's t test between two groups. The P-values less than 0.05 were considered significant.

RESULTS

Our results revealed that the serum levels of CXCL1, CXCL9 and CXCL12 were increased in GDMM, while no alteration was found in the serum levels of CXCL10 when compared to NPM. We have observed that in neonates the serum levels of angiogeneic chemokines followed an inverse fashion when compared to angiostasis chemokines. Interestingly, CXCL1 and CXCL12 were both increased in neonates who were delivered by GDMM, while, CXCL9 and CXCL10 were decreased in neonates delivered by GDMM.

Gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus, defined as diabetes diagnosed during pregnancy that is not clearly overt diabetes, is becoming more common as the epidemic of obesity and type 2 diabetes continues. Newly proposed diagnostic criteria will, if adopted universally, further increase the prevalence of this condition. Much controversy surrounds the diagnosis and management of gestational diabetes.

CONTENT

This review provides information regarding various approaches to the diagnosis of gestational diabetes and the recommendations of a number of professional organizations. The implications of gestational diabetes for both the mother and the offspring are described. Approaches to self-monitoring of blood glucose concentrations and treatment with diet, oral medications, and insulin injections are covered. Management of glucose metabolism during labor and the postpartum period are discussed, and an approach to determining the timing of delivery and the mode of delivery is outlined.

SUMMARY

This review provides an overview of current controversies as well as current recommendations for gestational diabetes care.

The impact of risk factors and more stringent diagnostic criteria of gestational diabetes on outcomes in central European women

OBJECTIVES

In the face of the ongoing discussion on the criteria for the diagnosis of gestational diabetes (GDM), we aimed to examine whether the criteria of the Fourth International Workshop Conference of GDM (WC) select women and children at risk better than the World Health Organization (WHO) criteria.

DESIGN AND SETTING

This was a prospective longitudinal open study in five tertiary care centers in Austria.

PATIENTS AND OUTCOME MEASURES

The impact of risk factors, different thresholds (WC vs. WHO), and numbers of abnormal glucose values (WC) during the 2-h, 75-g oral glucose tolerance test on fetal/neonatal complications and maternal postpartum glucose tolerance was studied in 1466 pregnant women. Women were treated if at least one value according to the WC (GDM-WC1) was met or exceeded.

RESULTS

Forty-six percent of all women had GDM-WC1, whereas 29% had GDM-WHO, and 21% of all women had two or three abnormal values according to WC criteria (GDM-WC2). Eighty-five percent of the GDM-WHO were also identified by GDM-WC1. Previous GDM [odds ratio (OR) 2.9], glucosuria (OR 2.4), preconceptual overweight/obesity (OR 2.3), age 30 yr or older (OR 1.9), and large-for-gestational age (LGA) fetus (OR 1.8) were the best independent predictors of the occurrence of GDM. Previous GDM (OR 4.4) and overweight/obesity (OR 4.0) also independently predicted diabetes postpartum. GDM-WC1 had a higher rate of obstetrical complications (LGA neonates, neonatal hypoglycemia, cesarean sections; P < 0.001) and impaired postpartum glucose tolerance (P < 0.0001) than GDM-WHO.

CONCLUSION

These results suggest the use of more stringent WC criteria for the diagnosis of GDM with the initiation of therapy in case of one fasting or stimulated abnormal glucose value because these criteria detected more LGA neonates with hypoglycemia and mothers with impaired postpartum glucose metabolism than the WHO criteria.

Pregnancy plasma glucose levels exceeding the American Diabetes Association thresholds, but below the National Diabetes Data Group thresholds for gestational diabetes mellitus, are related to the risk of neonatal macrosomia, hypoglycaemia and hyperbilirubinaemia

AIMS/HYPOTHESIS

Gestational diabetes mellitus (GDM) is a risk factor for perinatal complications. In several countries, the criteria for the diagnosis of GDM have been in flux, the American Diabetes Association (ADA) thresholds recommended in 2000 being lower than those of the National Diabetes Data Group (NDDG) that have been in use since 1979. We sought to determine the extent to which infants of women meeting only the ADA criteria for GDM are at increased risk of neonatal complications.

MATERIALS AND METHODS

In a multiethnic cohort of 45,245 women who did not meet the NDDG criteria and were not treated for GDM, we conducted nested case-control studies of three complications of GDM that occurred in their infants: macrosomia (birthweight >4,500 g, n = 494); hypoglycaemia (plasma glucose <2.2 mmo/l, n = 488); and hyperbilirubinaemia (serum bilirubin > or =342 micromol/l (20 mg/dl), n = 578). We compared prenatal glucose levels of the mothers of these infants and mothers of 884 control infants.

RESULTS

Women with GDM by ADA criteria only (two or more glucose values exceeding the threshold) had an increased risk of having an infant with macrosomia (odds ratio OR = 3.40, 95% CI = 1.55-7.43), hypoglycaemia (OR = 2.61, 95% CI = 0.99-6.92) or hyperbilirubinaemia (OR = 2.22, 95% CI = 0.98-5.04). Glucose levels 1 h after the 100-g glucose challenge that exceeded the ADA threshold were particularly strongly associated with each complication.

CONCLUSIONS/INTERPRETATION

These results lend support to the ADA recommendations and highlight the importance of the 1-h glucose measurement in a diagnostic test for GDM.

Nutrition and pregnancy: the link between dietary intake and diabetes

Pregnancy is a time when serial metabolic changes in the mother are carefully regulated to provide optimum substrate to both mother and fetus. Subtle perturbations in maternal metabolism can have implications not only for the index pregnancy, but also for future generations. The literature provides evidence that maternal nutrition plays a major role in the destiny of the offspring. Both maternal malnutrition and overnutrition are associated with subsequent diabetes in the offspring. Pregnancy represents a window of opportunity for health care providers to change dietary patterns toward habits that will be healthier for the individual now, as well as impacting on the future. The challenge for clinicians is to provide nutritional information based on scientific evidence that facilitates the normalization of fetal nutrition, and thus minimize the risk that the child will develop diabetes.

Epidemiology of gestational diabetes mellitus and its association with Type 2 diabetes

Gestational diabetes (GDM) is defined as carbohydrate intolerance that begins or is first recognized during pregnancy. Although it is a well-known cause of pregnancy complications, its epidemiology has not been studied systematically. Our aim was to review the recent data on the epidemiology of GDM, and to describe the close relationship of GDM to prediabetic states, in addition to the risk of future deterioration in insulin resistance and development of overt Type 2 diabetes. We found that differences in screening programmes and diagnostic criteria make it difficult to compare frequencies of GDM among various populations. Nevertheless, ethnicity has been proven to be an independent risk factor for GDM, which varies in prevalence in direct proportion to the prevalence of Type 2 diabetes in a given population or ethnic group. There are several identifiable predisposing factors for GDM, and in the absence of risk factors, the incidence of GDM is low. Therefore, some authors suggest that selective screening may be cost-effective. Importantly, women with an early diagnosis of GDM, in the first half of pregnancy, represent a high-risk subgroup, with an increased incidence of obstetric complications, recurrent GDM in subsequent pregnancies, and future development of Type 2 diabetes. Other factors that place women with GDM at increased risk of Type 2 diabetes are obesity and need for insulin for glycaemic control. Furthermore, hypertensive disorders in pregnancy and afterwards may be more prevalent in women with GDM. We conclude that the epidemiological data suggest an association between several high-risk prediabetic states, GDM, and Type 2 diabetes. Insulin resistance is suggested as a pathogenic linkage. It is possible that improving insulin sensitivity with diet, exercise and drugs such as metformin may reduce the risk of diabetes in individuals at high risk, such as women with polycystic ovary syndrome, impaired glucose tolerance, and a history of GDM. Large controlled studies are needed to clarify this issue and to develop appropriate diabetic prevention strategies that address the potentially modifiable risk factors.

Achieving Euglycaemia in Women with Gestational Diabetes Mellitus

Gestational diabetes mellitus is one of the major medical complications of pregnancy. Untreated, the mother and the unborn child may experience morbidity and fetal death may even occur. It is important to diagnose and treat all hyperglycaemia appearing during pregnancy. Ideally, a screening and diagnostic test that identified all women at risk for hyperglycaemia-associated complications would be employed in all pregnant women. Unfortunately, there is no such test available currently. The best alternative is to administer an oral glucose challenge test to all pregnant women and then apply the best strategies for interpretation. This article discusses the limitations of our present diagnostic tools and suggests an option for the clinician until the definitive test has been elucidated. In addition, this article outlines one dietary and management strategy that has been associated with an outcome of pregnancy that is similar to the outcome of pregnancies in healthy women. This strategy includes starting with a "euglycaemic" diet (comprising < 40% carbohydrates and > or =40% fat), which can then be individualised according to the patient's glucose levels. Appropriate exercise, such as arm ergometer training, may enhance the benefits of diet control. For patients who require insulin, if the fasting glucose level is >90 mg/dL or 5 mmol/L (whole blood capillary) then NPH insulin (insulin suspension isophane) should be given before bed, beginning with dosages of 0.2 U/kg/day. If the postprandial glucose level is elevated, pre-meal rapid-acting insulin should be prescribed, beginning with a dose of 1U per 10g of carbohydrates in the meal. If both the fasting and postprandial glucose levels are elevated, or if a woman's postprandial glucose levels can only be blunted if starvation ketosis occurs, a four-injections-per-day regimen should be prescribed. The latter can be based on combinations of NPH insulin and regular human insulin, timed to provide basal and meal-related insulin boluses. The total daily insulin dose for the four-injection regimen should be adjusted according to pregnant bodyweight and gestational week (0.7-1 U/kg/day); doses may need to be increased for the morbidly obese or when there is twin gestation. There is now some evidence that insulin lispro, other insulin analogues and oral antihyperglycaemic drugs may be beneficial in gestational diabetes, and more data on these agents are awaited with interest.

Testing for gestational diabetes

In 1996, the American Diabetes Association reported that 12% of total health care expenditure in the United States was spent on diabetes and its complications. Screening for and treating gestational diabetes results in improved perinatal morbidity and mortality. Moreover, detecting gestational diabetes identifies women who are at risk of future type 2 diabetes. This article reviews several approaches to diagnosing gestational diabetes.

Diagnostic criteria for gestational diabetes in relation to pregnancy outcome

OBJECTIVES

To determine which of the American Diabetes Association (ADA) or World Health Organization (WHO) plasma glucose criteria for gestational diabetes mellitus (GDM) best predicts poor fetal outcome. To determine whether an alternative cut-off point would result in increased predictive value and greater diagnostic effectiveness in pregnancies at high risk for GDM.

RESEARCH DESIGN AND METHODS

A sample of 473 successive apparently normal pregnant women attending the Obstetric Department were screened for GDM using both the ADA and the WHO criteria. Between 26 and 30 weeks of gestation, they underwent, on subsequent days, a screening test with a 50-g oral glucose load and two oral glucose tolerance tests (OGTTs) with 75 and 100 g of glucose according to the WHO and the ADA recommendations, respectively. From this group, we identified 99 women at high risk for GDM, who did not attend their pregnancy follow-up and whose delivery records were recovered at our hospital or in neighbouring hospitals. This unusual situation enabled us to study the natural history and outcome of their pregnancy in spite of not receiving special management usually provided to such women. As macrosomia was expected to be the most frequent undesirable foetal outcome, sensitivity and specificity calculations have been based on this outcome.

RESULTS

The study population (n=99) had a median parity of two and 14% had abnormal results in the 2-h, 75-g load test (WHO) vs. 6% in the 100-g test (ADA). Optimal cut-off points for each test were lower than those recommended for diagnosis by the ADA and the WHO. The optimal sensitivity for the 1-h, 50-g test was 66.7% (cut-off 137 mg/dl), and for the 2-h, 75-g test (cut-off 119 mg/dl). The best specificity and positive predictive value was for this last test with a cut-off point of 140 mg/dl in the second hour.

CONCLUSIONS

The standard 2-h cut-off value of 140 mg/dl for the 75-g test, as now recommended by WHO, was optimal for predicting macrosomia. Based on the sensitivity and specificity for macrosomia, the 1-h, 50-g screening test had an optimal cut-off point of 137 mg/dl (vs. 140 mg/dl recommended by ADA). The 2-h, 75-g OGTT value using a cut-off point of 119 mg/dl had equivalent sensitivity, specificity, and positive predictive value. In contrast, the 100-g OGTT had much lower levels of sensitivity, but higher specificity and higher positive predictive value.

The contentious nature of gestational diabetes: diet, insulin, glyburide and metformin

Gestational diabetes (GD) develops because pregnancy increases requirements for insulin secretion while increasing insulin resistance. Women with GD often have impaired pancreatic beta-cell compensation for insulin resistance. The nature of GD is currently contentious, with debate about its existence, diagnosis and ramifications for both mother and offspring from pregnancy into later life. Also contentious are the outcomes of intervention with diet, insulin, glyburide (Glynase trade mark, Pharmacia Upjohn) and metformin (Glucophage trade mark, Bristol-Myers Squibb). There is consensus that women with unequivocal GD have a significant risk of adverse perinatal outcomes and increased risk of later type 2 diabetes mellitus. Foetuses from pregnancies with GD have a higher risk of macrosomia (associated with higher rate of birth injuries), asphyxia, and neonatal hypoglycaemia and hyperinsulinaemia. Uncontrolled GD predisposes foetuses to accelerated, excessive fat accumulation, insulin resistance, pancreatic exhaustion secondary to prenatal hyperglycaemia and possible higher risk of child and adult obesity and type 2 diabetes mellitus later in adult life. However, there is no consensus as to whether glucose intolerance of a severity below unequivocal GD is related to adverse maternal, fetal or perinatal outcomes, and whether this relationship is a continuous one. If dietary intervention is not sufficient in the treatment of GD, then, historically, insulin has been added. Recent studies suggest that glyburide may be efficaciously substituted for insulin. Preliminary studies suggest that metformin may have the unique potential to prevent the development of GD.

Prevalence of gestational diabetes mellitus detected by the national diabetes data group or the carpenter and coustan plasma glucose thresholds

OBJECTIVE

In 2000, the American Diabetes Association proposed the adoption of the Carpenter and Coustan criteria for diagnosis of gestational diabetes mellitus (GDM). The Carpenter and Coustan cutoffs are lower than the previously recommended National Diabetes Data Group (NDDG) values and would result in higher prevalence of GDM. Our aim is to estimate the magnitude of change in prevalence of GDM using the Carpenter and Coustan thresholds as compared with the NDDG thresholds by age and ethnicity.

RESEARCH DESIGN AND METHODS

Cross-sectional study of 28,330 women aged 14-49 years who gave birth in 1996 and were members of the Northern California Kaiser Permanente Medical Care Program. Age, ethnicity, screening, and diagnostic test results were assessed from computerized hospitalization and laboratory systems.

RESULTS

A total of 26,481 (94%) women were screened using a 50-g, 1-h oral glucose tolerance test, and 4,190 women underwent a diagnostic 100-g, 3-h oral glucose tolerance test after an abnormal screening. Overall, the GDM prevalence among screened women was 3.2% (95% CI 3.0-3.4) by NDDG and 4.8% (95% CI 4.5-5.1) by Carpenter and Coustan criteria, and based on either threshold, it increased with age (P < 0.001). The age-adjusted GDM prevalence by NDDG and Carpenter and Coustan criteria, respectively, was 5.0 and 7.4% in Asians, 3.9 and 5.6% in Hispanics, 3.0 and 4.0% in African-Americans, and 2.4 and 3.8% in whites. Proportional increments were larger in women aged <25 years (70%) and in whites (58%).

CONCLUSIONS

-The prevalence of GDM increased, on average, by 50% with use of the Carpenter and Coustan thresholds. Relative increments were greater in low-risk age and ethnic groups. This information would be useful for clinical settings in predicting cost of GDM based on demographic characteristics of the population.

The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study

OBJECTIVE

The objective of the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study is to clarify unanswered questions on associations of maternal glycemia, less severe than overt diabetes mellitus, with risks of adverse pregnancy outcome. This report describes the background and design of the HAPO Study.

METHODS

HAPO is a 5-year investigator-initiated prospective observational study that will recruit approximately 25000 pregnant women in 10 countries. HAPO utilizes a Central Laboratory for measurement of key metabolic variables, a Clinical Coordinating Center, a Data Coordinating Center, and an independent Data Monitoring Committee. Glucose tolerance is assessed by a 75 g 2-h OGTT at 24-32 weeks' gestation. Results are unblinded to the woman and her caregivers if: fasting plasma glucose >5.8 mmol/l, 2-h plasma glucose >11.1 mmol/l or any plasma glucose <2.5 mmol/l. Random plasma glucose measurement is performed at 34-37 weeks or if symptoms suggest hyperglycemia; results are unblinded for values > or = 8.9 mmol/l. Sociodemographic and health history data are collected via questionnaire and medical record abstraction. Maternal blood is obtained for measurement of serum C-peptide and hemoglobin A1c (HbA(1C)), cord blood for serum C-peptide and plasma glucose, and a capillary specimen is taken between 1 and 2 h following delivery for neonatal plasma glucose. Neonatal anthropometrics are obtained, and follow-up data are collected at 4-6 weeks post-delivery. The primary outcomes to be assessed in relation to maternal glycemia are cesarean delivery, increased fetal size (macrosomia/LGA/obesity), neonatal morbidity (hypoglycemia), and fetal hyperinsulinism.

Can glucose tolerance test predict fetal hyperinsulinism?

OBJECTIVE

To establish cut off levels for oral glucose tolerance test in pregnancy using fetal hyperinsulinism as a clinical endpoint.

DESIGN

Capillary blood glucose levels at 0, 1, and 2 hours after the ingestion of either 1 g/kg or 75 g glucose, at 28 (SD 5) weeks of gestation were analysed in 220 women with elevated amniotic fluid insulin levels [> or =42 pmol/L (> or =7 microU/mL)] after a mean (SD) of 31 weeks (3) and in 220 nondiabetic controls.

RESULTS

In women with elevated amniotic fluid insulin levels the mean (SD) capillary blood glucose values at 0, 1, and 2 hours were 5.2 mmol/L (1.0) [94 mg/dL (18)], 10.5 mmol/L (1.4) [189 mg/dL (25)] and 8.2 mmol/L (2.0) [147 mg/dL (36)], respectively. The one-hour value had the highest sensitivity to predict elevated amniotic fluid insulin levels. The 5th centile of the one-hour blood glucose levels representing a detection rate of 95% was 8.9 mmol/L (160 mg/dL).

CONCLUSION

Glucose cut off levels in most established oral glucose tolerance test criteria are too high, to accurately predict amniotic fluid hyperinsulinism. A one-hour test may be sufficient for detecting amniotic fluid hyperinsulinism. Since different loads (1 g/kg, 75 g or 100 g) and blood fractions (venous plasma or capillary blood) have minimal impact on oral glucose tolerance test results, a single one-hour cut off of 8.9 mmol/L (160 mg/dL), independent of the sampling method, may be appropriate for the diagnosis of gestational diabetes mellitus severe enough to cause amniotic fluid hyperinsulinism.

Comparison of the validity of the criteria for gestational diabetes mellitus by WHO and by the Japan Society of Obstetrics and Gynecology by the outcomes of pregnancy

Data for 416 Japanese pregnant women who received a 75g oral glucose tolerance test (OGTT) for determination of gestational diabetes mellitus (GDM) in 13 hospitals in Japan were analyzed retrospectively. Comparison of the diagnostic criteria of the World Health Organization (WHO) and the Japan Society of Obstetrics and Gynecology (JSOG) revealed pregnant women who met the latter criteria for GDM to have significantly higher incidences of low Apgar scores, respiratory problems, neonatal hypoglycemia, preterm delivery and requirements for insulin therapy and cesarean section. The women who met the WHO criteria but not the JSOG criteria had minor complications. These observations suggest that the GDM criteria of the JSOG are more appropriate than the WHO criteria from the standpoint of therapeutic intervention for pregnant women.

Hypertensive disorders, diabetes mellitus, and anemia: three common medical complications of pregnancy

Hypertensive disorders, diabetes mellitus, and anemia are three common medical complications of pregnancy. In many cases, primary care physicians manage them. The understanding of these conditions and recommendations for their treatment are in constant evolution. Care for patients with these problems requires a working knowledge of current information. This article reviews the current knowledge about and treatment of these three disorders.

The diagnosis and classification of gestational diabetes mellitus: is it time to change our tune?

OBJECTIVE

This study was designed to determine the impact on our population of adopting the Carpenter and Coustan criteria for gestational diabetes mellitus in place of the currently used National Diabetes Data Group criteria, to review the evidence supporting replacement of the National Diabetes Data Group criteria with the Carpenter and Coustan criteria, and to propose analogous diagnostic criteria for diabetes in pregnant and nonpregnant women.

STUDY DESIGN

The National Diabetes Data Group criteria and the proposed Carpenter and Coustan criteria were both used to retrospectively review medical records of patients screened for gestational diabetes mellitus during 1995 and 1996 in the Kaiser Permanente Northwest Division. Computerized search was performed on automated data systems and software was used for statistical analyses. A MEDLINE review of relevant literature was conducted.

RESULTS

Of 8857 pregnant women screened for gestational diabetes in 1995 and 1996, 284 (3.21%) met the National Diabetes Data Group criteria, whereas 438 (4.95%) met the Carpenter and Coustan criteria. We estimate that in our population use of the Carpenter and Coustan criteria in 1996 could at best have reduced the prevalence of infants weighing >/=4000 g from 17.1% to 16.9% and the prevalence of infants weighing >/=4500 g from 2.95% to 2.91%.

CONCLUSIONS

Replacing the National Diabetes Data Group criteria with the Carpenter and Coustan criteria would increase by 54% the number of pregnant women with a diagnosis of gestational diabetes mellitus and would also increase costs, while only minimally affecting prevalence of infant macrosomia. The medical literature does not provide compelling evidence for adopting the Carpenter and Coustan criteria. Standardization of both measurement of venous plasma glucose level and diagnostic criteria for gestational diabetes mellitus is an important goal. Parallel criteria for diagnosis and classification of diabetes mellitus in pregnant and nonpregnant women should be developed.

Toward universal criteria for gestational diabetes: relationships between seventy-five and one hundred gram glucose loads and between capillary and venous glucose concentrations

OBJECTIVES

Replacement of the two-step, 100 gm, 3-hour National Diabetes Data Group procedure by the one-step, 75 gm, 2-hour World Health Organization oral glucose tolerance test has been hindered by a paucity of data comparing the two tests during pregnancy. The current series compared 100 gm and 75 gm glucose loads and glucose measurements in venous plasma or capillary blood.

STUDY DESIGN

After a 75 gm oral glucose tolerance test 30 gestational diabetics and 30 metabolically healthy pregnant women were randomly assigned to a second 75 or 100 gm test within 3+/-1.3 (mean+/-SD) days. Glucose levels at both tests was measured in capillary blood and venous plasma, as were insulin and C peptide.

RESULTS

In controls 1-hour maternal glucose levels (112 vs 128 mg/dl) and 2-hour levels (104 vs 113 mg/dl) differed significantly after a 75 or 100 gm load (paired t test). In gestational diabetes mellitus, however, there was no difference (176 vs 178 mg/dl) but a low insulin/glucose quotient at 1 hour. Only 2-hour levels differed significantly (133 vs 149 mg/dl). In controls glucose measurement in capillary blood and venous plasma differed significantly at 1 hour (126 vs 115 mg/dl) and 2 hours (111 vs 104 mg/dl) independently of the glucose load. In gestational diabetes mellitus, however, glucose measurement in capillary blood and venous plasma differed neither in 1-hour levels (179 vs 174 mg/dl) nor in 2-hour levels (142 vs 139 mg/dl).

CONCLUSION

In metabolically healthy women both different loading and different blood fractions lead to statistically different blood glucose levels at 1 and 2 hours. In gestational diabetes mellitus, however, 1-hour glucose levels do not differ after a 75 or 100 gm load or after glucose measurement in capillary blood or venous plasma. This is due to elevated insulin resistance shown by a low insulin/glucose quotient at 1 hour. For comparison of tests in gestational diabetes mellitus only, 2-hour values must be adjusted by 16 mg/dl after different loading.

Management of gestational diabetes mellitus

This article addresses management of gestational diabetes in a two part fashion. It discusses the pathophysiology and pathogenesis of diabetes and outlines the contemporary management approach for gestational diabetes in the 1990s.

Screening and testing for gestational diabetes mellitus

Gestational diabetes mellitus is defined as carbohydrate intolerance of variable severity first diagnosed during pregnancy. Although universal screening for gestational diabetes mellitus is practiced by more than 75% of obstetricians in the United States, agreement is lacking worldwide regarding the appropriateness of this approach. This article discusses the assumption that some type of screening program is desirable and considers how best to conduct screening and diagnostic testing for gestational diabetes mellitus.

Gestational diabetes survey

OBJECTIVE

Our purpose was to determine how residents in obstetrics and gynecology and fellows in maternal-fetal medicine are currently being trained to diagnose and manage gestational diabetes mellitus.

STUDY DESIGN

Questionnaires were mailed to 202 obstetrics and gynecology residency program directors and 78 maternal-fetal medicine fellowship directors.

RESULTS

Sixty-four (82%) of the maternal-fetal medicine directors versus 142 (70%) of the residency directors responded. Universal screening, use of a 50 gm glucose challenge with a 1-hour-postingestion sample, no requirements for fasting before the screening test, use of two abnormal values on the 3-hour glucose tolerance test to define gestational diabetes mellitus, and initiation of insulin for elevated fasting glucose levels in spite of diet therapy were each recommended by > 90% of the respondents.

CONCLUSION

Although the optimal management of gestational diabetes mellitus remains controversial, program directors are in general agreement with many aspects of the diagnosis and management.

Gestational diabetes diagnostic criteria: long-term maternal follow-up

OBJECTIVE

The purpose of this study was to determine if the risk of having diabetes later in life was different in those who were gestational diabetic by Coustan criteria and not by National Diabetes Data Group criteria and those who are gestational diabetic only by National Diabetes Data Group criteria.

STUDY DESIGN

Between 1988 and 1990, 331 patients from the Springfield area who were diagnosed as gestational diabetic by either criteria since 1975 were examined for the development of diabetes by history or by 2-hour, 75 gm glucose tolerance test. National Diabetes Data Group criteria were used to determine normality or diabetic abnormality. Variables associated with diabetes were obtained. The data were analyzed using three groups: (1) gestational diabetic by National Diabetes Data Group criteria, (2) gestational diabetic by Coustan's criteria only, and (3) both groups 1 and 2.

RESULTS

Group 1 had 190 (57.4%) and group 2 had 141 patients (42.6%), of which 25.3% and 25.5% had diabetic abnormality, respectively. Variables predictive for the development of diabetic abnormality were glucose tolerance test fasting value, number of gestational diabetic pregnancies, time to follow-up, and prepregnancy weight index. There were no differences in these variables between the normal patients or those with diabetic abnormality in groups 1 and 2.

CONCLUSION

Because Coustan criteria classify an additional 68.9% patients who have the same risk and risk factors for later development of diabetic abnormality and pregnancy complications compared with patients who are gestational diabetic by National Diabetes Data Group criteria, the criteria of Carpenter and Coustan should be adopted as the standard for diagnosing gestational diabetes.

Impact of time since last meal on the gestational glucose challenge test. The Toronto Tri-Hospital Gestational Diabetes Project

OBJECTIVE

The purpose of the study was to evaluate the impact of time since the last meal on the glucose challenge test and to find cut points that are most likely to predict the outcome of the oral glucose tolerance test in patients screened for gestational diabetes.

STUDY DESIGN

This prospective analytic cohort study was carried out at the University of Toronto Perinatal Complex. A 50 gm glucose load was given at 26 weeks' gestation and the time since previous meal ingestion was recorded. At 28 weeks' gestation a 100 gm oral glucose tolerance test was administered. A total of 4274 eligible patients were screened.

RESULTS

Time since the last meal had a marked effect on mean plasma glucose. Receiver-operator characteristic curve analysis with National Diabetes Data Group criteria to interpret the oral glucose tolerance allowed the selection of the most efficient cut points for the glucose challenge test on the basis of time since the last meal. These cut points were 8.2, 7.9, and 8.3 mmol/L for elapsed postprandial times of < 2, 2 to 3, and > 3 hours, respectively. With this change from the current threshold of 7.8 mmol/L the number of patients with a positive screening test dropped from 18.5% to 13.7%. There was an increase in positive predictive value from 14.4% to 18.7%. The rate of patient misclassification fell from 18.0% to 13.1%.

CONCLUSION

We suggest that screening strategies for detection of gestational diabetes be reconsidered, to account for the impact of variable postprandial status on the test results.

Maternal characteristics, neonatal outcome, and the time of diagnosis of gestational diabetes

OBJECTIVE

A study was undertaken to evaluate the yield of early, routine screening for gestational diabetes and to determine whether maternal characteristics and neonatal outcome differ according to the time of diagnosis.

STUDY DESIGN

A total of 2776 women were screened before 24 weeks of gestation, and each was delivered of a singleton infant on the clinic service of Mount Sinai Hospital in New York City between January 1986 and January 1991.

RESULTS

An abnormal glucose tolerance test was diagnosed in 102 women < 24 weeks and in 252 patients at > or = 24 weeks of gestation. Logistic regression analysis showed that the group diagnosed early was significantly older and more likely to have hypertensive disorders and low maternal weight gain and to require insulin treatment, compared with the group diagnosed late. No significant differences were evident in neonatal outcome.

CONCLUSIONS

These data indicate that a sizable proportion of patients with gestational diabetes can be diagnosed early in pregnancy. The differences in maternal characteristics and insulin requirements between the early- and late-diagnosis groups also suggest heterogeneity of gestational diabetes or the possibility of preexisting impaired glucose intolerance in the early-diagnosis group.

The role of repeat glucose tolerance tests in the diagnosis of gestational diabetes

The diagnosis of gestational diabetes requires that two of the four 100 gm, 3-hour oral glucose tolerance test values be elevated. Our report evaluates the usefulness of repeating the oral glucose tolerance test in patients who have only one abnormal value. One hundred six patients who had abnormal results of diabetes screening tests (glucose level greater than or equal to 130 mg/dl) and whose glucose tolerance test had one abnormal value underwent repeat glucose tolerance testing at an average of 4.6 weeks later. Thirty-six patients (34%) had two abnormal values on the repeat test and were classified as having gestational diabetes. Our results indicate that the finding of one abnormal value on a glucose tolerance test denotes a significant risk for the development of gestational diabetes.

Gestational diabetes mellitus: evidence for autoimmunity against the pancreatic beta cells

Diabetes mellitus is a frequent transient or rare permanent complication of pregnancy. The role of autoimmune phenomena in this gestational form of diabetes is incompletely understood. We have examined sera from 312 pregnant women who had abnormal glucose tolerance (based on a screening examination during the second trimester) for the presence of islet cell surface antibodies or insulin autoantibodies. Fifty-eight of these women were lost to follow-up. Of the remaining subjects, 144 (57.1%) had gestational diabetes diagnosed by formal glucose tolerance testing and the others (42.9%) were normal. Sixty percent of the women with gestational diabetes eventually required insulin to control their blood glucose during pregnancy. One serum from the non-diabetic women was positive for insulin antibodies (0.9%); 8 of the sera from the patients with gestational diabetes were positive (5.6%). Subsequent analysis revealed that all nine of the women whose sera were positive for insulin autoantibodies had been treated with insulin previously. Islet cell surface antibodies were strongly correlated with gestational diabetes. Forty-five of 144 gestational diabetic sera were positive (31.3%) whereas only 9 of 108 suspect control sera (8.3%) and 7 of 60 unknown sera (11.7%) were positive. These data suggest that a high percentage of pregnant women who screen positive for glucose intolerance have serological evidence of an autoimmune response against the pancreatic islets, in spite of the state of relative immune tolerance during pregnancy. These data suggest that autoimmune phenomena may play a role in gestational diabetes and that the presence of islet cell antibodies can predict insulin-requiring gestational diabetes.

Screening and diagnosis of gestational diabetes

This chapter discusses the evidence for the existence of an entity called 'gestational diabetes', suggesting that it can be understood in terms of risk to the pregnancy and/or risk to the mother. Various diagnostic criteria used in various parts of the world are described, and a rationale for using pregnancy-specific criteria is put forth. Universal screening approaches are also characterized. Barriers to the universal adoption of a single screening scheme and set of diagnostic criteria are outlined.

Reproducibility of the oral glucose tolerance test in pregnancy

This prospective investigation evaluated the reproducibility of the 100 gm oral glucose tolerance test. Sixty-four obstetric patients with greater than or equal to 135 mg/dl on the 50 gm oral glucose screening test were scheduled for the 100 gm test. All patients repeated the oral glucose tolerance test in 1 to 2 weeks. Both tests included a preparatory diet, and testing conditions were identical. There were no significant differences in the mean test values at each testing interval when the entire study population was considered. Patients were then divided into four groups according to the outcome of the two tests. Forty-eight of 64 (75%) had normal results at each testing period (group 1); 11 of 64 (17%) had initially normal results and abnormal results on retest (group 2); 3 of 64 (5%) had initially abnormal results and normal results on retest (group 3); 2 of 64 (3%) had abnormal results at both testing phases (group 4). There were no significant differences between oral glucose tolerance test results within groups 1 and 4. However, significant differences occurred within groups 2 and 3 between the two tests. Group 2 patients had a greater frequency of an abnormal 1-hour value on the test than group 1 patients (p = 0.001). Overall, the reproducibility of the oral glucose tolerance test was 78% (50 of 64). We recommend the oral glucose tolerance test be repeated when the 1-hour value is abnormal or when the fasting blood sugar, 1-hour, and 2-hour values are near the upper end of the normal range.