Toward universal criteria for gestational diabetes: the 75-gram glucose tolerance test in pregnancy

When and how to start insulin treatment in gestational diabetes: a UK perspective

Gestational diabetes mellitus, however currently defined, is relatively rare in a UK Caucasian population, but is much more common in other ethnic groups. There is likely soon to be better agreement on diagnostic levels of hyperglycaemia in pregnancy, but there is still considerable reluctance to start insulin therapy. There is now good evidence that insulin administered twice daily during the third trimester to mothers who have even a mild degree of hyperglycaemia will reduce fetal size, and in particular fetal adiposity. In relation to recent concepts of the transgenerational passage of Type 2 diabetes and obesity, further epidemiological investigation is required. Insulin treatment in pregnancy may also prove to have a role in prevention of Type 2 diabetes in the next generation.

A randomized controlled trial using glycemic plus fetal ultrasound parameters versus glycemic parameters to determine insulin therapy in gestational diabetes with fasting hyperglycemia

OBJECTIVE

To compare management based on maternal glycemic criteria with management based on relaxed glycemic criteria and fetal abdominal circumference (AC) measurements in order to select patients for insulin treatment of gestational diabetes mellitus (GDM) with fasting hyperglycemia.

RESEARCH DESIGN AND METHODS

In a pilot study, 98 women with fasting plasma glucose (FPG) concentrations of 105-120 mg/dl were randomized. The standard group received insulin treatment. The experimental group received insulin if the AC, measured monthly, was > or =70th percentile and/or if any venous FPG measurement was >120 mg/dl. Power was projected to detect a 250-g difference in birth weights.

RESULTS

Gestational ages, maternal glycemia, and AC percentiles were similar at randomization. After initiation of protocol, venous FPG (P = 0.003) and capillary blood glucose levels (P = 0.049) were significantly lower in the standard group. Birth weights (3,271 +/- 458 vs. 3,369 +/- 461 g), frequencies of birth weights >90th percentile (6.3 vs 8.3%), and neonatal morbidity (25 vs. 25%) did not differ significantly between the standard and experimental groups, respectively. The cesarean delivery rate was significantly lower (14.6 vs. 33.3%, P = 0.03) in the standard group; this difference was not explained by birth weights. In the experimental group, infants of women who did not receive insulin had lower birth weights than infants of mothers treated with insulin (3,180 +/- 425 vs. 3,482 +/- 451 g, P = 0.03).

CONCLUSIONS

In women with GDM and fasting hyperglycemia, glucose plus fetal AC measurements identified pregnancies at low risk for macrosomia and resulted in the avoidance of insulin therapy in 38% of patients without increasing rates of neonatal morbidity.

Higher carbohydrate intake is associated with decreased incidence of newborn macrosomia in women with gestational diabetes

OBJECTIVE

To study the influence of energy and macronutrient intake on infant birthweight in women with gestational diabetes mellitus undergoing intensive management.

DESIGN

This prospective study evaluated the impact of intensive management of gestational diabetes on maternal and fetal morbidity, and addressed the relationship between food intake and infant birthweight.

SETTING

Fifteen maternity hospitals in northern France.

SUBJECTS

Ninety-nine women with gestational diabetes or gestational mild hyperglycemia diagnosed between 24 and 34 weeks of gestation were surveyed. After 1 was excluded because of a premature birth and 18 were excluded as underreporters, 80 women were included in the final analysis. Diet intake was assessed by a dietary history at the first interview, and by two 3-day diet records at the 3rd and 7th week after diagnosis.

RESULTS

In a forward-stepwise regression analysis (controlling for maternal age; smoking; parity; prepregnancy BMI; pregnancy weight gain; gestational duration; infant sex; fasting and 2-hour postprandial serum glucose; insulin therapy; and energy, fat, protein and carbohydrate intake during treatment) infant birthweight was positively associated with gestational duration (beta = +0.34, P<.002), and negatively with smoking (beta = -0.27, P<.02) and carbohydrate intake (beta = -0.24, P<.03). There were no large-for-gestational-age infants among women whose carbohydrate intake exceeded 210 g/day.

CONCLUSION

For women with gestational diabetes undergoing intensive management, higher carbohydrate intake is associated with decreased incidence of macrosomia.

APPLICATION

These findings suggest that nutrition counseling in gestational diabetes must be directed to maintain a sufficient carbohydrate intake (at least 250 g per day), which implies a low-fat diet to limit energy intake. A careful distribution of carbohydrate throughout the day and the use of low-glycemic index foods may help limit postprandial hyperglycemia.

The utility of a single test to identify women at risk for gestational diabetes

A number of single tests have been proposed as both screening and definitive tests of glucose intolerance during pregnancy. Despite limitations imposed by a lack of uniformity in methodology and definitions of gestational diabetes mellitus, there appears to be an independent relationship between some single-test results and clinically meaningful outcomes. Further study is needed to identify those glucose values above which women and their babies who are at risk for glycemia-related adverse outcomes may be identified.

Clinical impact of mild carbohydrate intolerance in pregnancy: a study of 2904 nondiabetic Danish women with risk factors for gestational diabetes mellitus

OBJECTIVE

The objective was to study the clinical impact of mild carbohydrate intolerance in pregnant women with risk factors for gestational diabetes mellitus.

STUDY DESIGN

This was a historical cohort study of 2904 pregnant women examined for gestational diabetes on the basis of risk factors. Information on oral glucose tolerance test results and clinical outcomes was collected from laboratory charts and medical records.

RESULTS

The following outcomes increased significantly with increasing glucose values during the oral glucose tolerance test: shoulder dystocia, macrosomia, emergency cesarean section, assisted delivery, hypertension, and induction of labor. However, when corrections were made for other risk factors, hypertension and induction of labor were only marginally associated with glucose levels.

CONCLUSION

In a group of nondiabetic pregnant women with risk factors for gestational diabetes, there was a graded increase in the frequency of shoulder dystocia and other maternal-fetal complications with increasing glucose levels during an oral glucose tolerance test.

Gestational diabetes mellitus diagnosed with a 2-h 75-g oral glucose tolerance test and adverse pregnancy outcomes

OBJECTIVE

To evaluate American Diabetes Association (ADA) and World Health Organization (WHO) diagnostic criteria for gestational diabetes mellitus (GDM) against pregnancy outcomes.

RESEARCH DESIGN AND METHODS

This cohort study consecutively enrolled Brazilian adult women attending general prenatal clinics. All women were requested to undertake a standardized 2-h 75-g oral glucose tolerance test (OGTT) between their estimated 24th and 28th gestational weeks and were then followed to delivery. New ADA criteria for GDM require two plasma glucose values > or = 5.3 mmol/l (fasting), > or = 10 mmol/l (1 h), and > or = 8.6 mmol/l (2 h). WHO criteria require a plasma glucose > or = 7.0 mmol/l (fasting) or > or = 7.8 mmol/l (2 h). Individuals with hyperglycemia indicative of diabetes outside of pregnancy were excluded.

RESULTS

Among the 4,977 women studied, 2.4% (95% CI 2.0-2.9) presented with GDM by ADA criteria and 7.2% (6.5-7.9) by WHO criteria. After adjustment for the effects of age, obesity, and other risk factors, GDM by ADA criteria predicted an increased risk of macrosomia (RR 1.29, 95% CI 0.73-2.18), preeclampsia (2.28, 1.22-4.16), and perinatal death (3.10, 1.42-6.47). Similarly, GDM by WHO criteria predicted increased risk for macrosomia (1.45, 1.06-1.95), preeclampsia (1.94, 1.22-3.03), and perinatal death (1.59, 0.86-2.90). Of women positive by WHO criteria, 260 (73%) were negative by ADA criteria. Conversely, 22 (18%) women positive by ADA criteria were negative by WHO criteria.

CONCLUSIONS

GDM based on a 2-h 75-g OGTT defined by either WHO or ADA criteria predicts adverse pregnancy outcomes.

To screen or not to screen for gestational diabetes mellitus. The clinical quagmire

Although there continues to be a lack of agreement about the most appropriate way to screen for GDM, screening remains the standard of care in this country. Universal screening of all pregnant women maximizes sensitivity but has significant financial implications because of its increased costs. Additional studies are needed that apply cost-analysis to various screening protocols to identify cost-effective screening strategies.

Evidence-based diabetes screening during pregnancy

The concept of gestational diabetes was described more than a half century ago and has been studied extensively for more than 30 years. Available data indicate that the prevalence is highly variable, probably reflecting underlying risk factors. In addition, gestational diabetes is not a specific disease, but rather an abnormal laboratory value. Criteria for diagnosis are variable, and there is little agreement about who should be screened, if screening should be selective or universal, or how screening should be performed. Moreover, the most commonly used criteria in the United States differ from the European and World Health Organization standard criteria. This article describes the background for diabetes testing, current evidence for testing and diagnosis in pregnant women, "risks" of diagnosis, and various screening procedures and protocols, using data-based evidence when available. Midwifery practice recommendations are also made, including examination of risk factors as clinical decisions are made about guidelines.

Selective versus universal screening for gestational diabetes mellitus: an evaluation of predictive risk factors

OBJECTIVE

To assess whether selective screening for gestational diabetes mellitus (GDM) on the basis of risk-factor assessment is a practicable alternative to universal screening.

DESIGN

Case-control study.

SETTING

A 212-bed regional specialist hospital in Melbourne, providing services in obstetrics and gynaecology, paediatrics, geriatrics and rehabilitation.

SUBJECTS

6,032 women who gave birth at the hospital, May 1996 to August 1997 and November 1997 to August 1998; all were screened for GDM, and 313 were diagnosed with the condition.

MAIN OUTCOME MEASURES

Odds ratios (ORs) for risk factors (age, obesity, family history of diabetes mellitus and high-risk racial heritage) in women with GDM compared to those without GDM; proportion of women with GDM whose diagnosis would have been missed by selective screening.

RESULTS

ORs were 1.9 for age > or = 25 years (95% CI, 1.3-2.7), 2.3 for body mass index > or = 27kg/m2 (95% CI, 1.6-3.3), 2.5 for high-risk racial heritage (95% CI, 2.0-3.2), and 7.1 for family history of diabetes mellitus (95% CI, 5.6-8.9). Other proposed criteria (previous GDM and glycosuria) added no further diagnostic power. Selective screening using the above four criteria would have missed two of 313 cases (0.6%) and could have saved screening up to 1,025 women without GDM (17% of all women).

CONCLUSIONS

Selective screening for GDM based on prior risk assessment can reduce the need for testing, with negligible loss of diagnostic efficiency.

A comparison of costs associated with screening for gestational diabetes with two-tiered and one-tiered testing protocols

OBJECTIVE

The Fourth International Workshop on Gestational Diabetes recently suggested that two techniques, a 2-tiered protocol and a 1-tiered protocol, to screen for gestational diabetes mellitus are acceptable alternatives. This study was undertaken to compare the direct costs and patient time expenditures associated with implementing both techniques.

STUDY DESIGN

A MEDLINE search was undertaken to determine the prevalence of positive and negative screening results. Direct costs of testing were estimated by determining the range of supply costs from manufacturers' catalogs and the labor costs by estimating the time required to perform each procedure and multiplying by the appropriate range of wages; these costs were then multiplied by the appropriate range of the number of procedures required to implement both protocols, and the totals were summed. Patient time expended was estimated by assigning test times of 1, 2, and 3 hours for the 50-g screening glucose challenge test, the 75-g oral glucose tolerance test, and the 100-g oral glucose tolerance test, respectively. If additional visits were required, 2 travel-time units were assigned each time a patient underwent a procedure. These units were multiplied by the range of patients undergoing various tests to implement the alternative protocols.

RESULTS

We identified low and high direct costs, test times, and travel units per patient screened by the 1- and 2-tiered testing protocols. Low and high direct costs were $3.46 and $7.88, respectively, for the 2-tiered protocol and $5.64 and $10.88, respectively, for the 1-tiered protocol (relative ratios, 1.63 for low direct costs in each protocol and 1.38 for high direct costs in each protocol). Low and high test times were 1.4 and 1.5 hours, respectively, for the 2-tiered protocol and 2.0 and 2.0 hours, respectively, for the 1-tiered protocol (relative ratios, 1.47 for low test times in each protocol and 1.32 for high test times in each protocol). Low and high travel units for the 2-tiered protocol were 0.2 and 0.3, respectively, when the glucose challenge test was given at the prenatal visit, and 2.2 and 2.3, respectively, when the test was not given at that time. Low and high travel units for the 1-tiered protocol were 8.3 and 5.8, respectively, when the glucose challenge test was given at the prenatal visit, and 0.89 and 0.85, respectively, when the test was not given at that time.

CONCLUSIONS

The 2-tiered protocol appears to be associated with lower direct implementation costs and less patient time expenditure than the 1-tiered scheme. The 1-tiered protocol is associated with slightly less travel time, but this is unlikely to offset the test time advantage of the 2-tiered protocol. Until further data regarding the relative clinical utility of the 2 protocols become available, these factors may be important for clinicians in deciding which screening format to follow.

Impaired glucose tolerance associated with adverse pregnancy outcome: a population-based study in southern Sweden

OBJECTIVE

We conducted a population-based study of maternal and neonatal characteristics and delivery complications in relation to the outcome of a 75-g, 2-hour oral glucose tolerance test at 25 to 30 weeks' gestation.

STUDY DESIGN

An oral glucose tolerance test was offered to pregnant women in a geographically defined population. Pregnancy outcome was analyzed according to the test result.

RESULTS

Among women delivered at Lund Hospital, we identified 4526 women with an oral glucose tolerance value of <7.8 mmol/L (<140 mg/dL), 131 women with a value of 7.8 to 8.9 mmol/L (140-162 mg/dL), and 116 women with gestational diabetes (> or =9.0 mmol/L [> or =162 mg/dL]). A further 28 cases of gestational diabetes were identified, giving a prevalence of 1.2%. An increased rate of cesarean delivery and infant macrosomia was observed in the group with a glucose tolerance value of 7.8 to 8.9 mmol/L (140-162 mg/dL) and in the gestational diabetes group. Advanced maternal age and high body mass index were risk factors for increased oral glucose tolerance values in 12,657 screened women in the area.

CONCLUSION

The study stresses the significance of moderately increased oral glucose tolerance values.

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.

Fasting plasma glucose as a screening test for gestational diabetes in a multi-ethnic, high-risk population

AIMS

Screening every pregnant woman for gestational diabetes mellitus (GDM), as widely recommended for high-incidence populations, strains the healthcare system excessively. This study investigated the value of fasting plasma glucose (FPG) as an alternative to the more cumbersome oral glucose tolerance test (OGTT).

METHODS

One thousand six hundred and forty-four pregnant women in a multi-ethnic, high-risk population were evaluated by the FPG as a screening test among two principal subgroups, i.e. women (n = 1276) at risk for GDM on clinical grounds and those women (n = 368) with a positive post 50-g, 1-h plasma glucose challenge test (GCT). Two threshold values for FPG 'ruled in or ruled out' a GDM diagnosis, which was confirmed by the 3-h, 100-g OGTT, using Carpenter's modified criteria as the 'gold standard'.

RESULTS

In the women with a positive clinical history, at an optimal cut-off value of FPG < 4.4 mmol/l to rule out GDM; a sensitivity of 94.7% was achieved, 21 (1.6%) women being false negatives. Using a FPG > or = 5.3 mmol/l to rule in GDM; the specificity was 94.0% with 53 (4.2%) women being classified as false positives. FPG would have eliminated need for the OGTT in 50.9% pregnant women (misclassification rate 5.8%). In the positive GCT group, using similar cut-offs for FPG, a sensitivity of 96.6% and specificity of 90.8% was achieved with a potential to avoid 51.6% OGTTs (misclassification rate 7.3%). The positive predictive value of the GCT was 31.8% compared to 80.2% for FPG at 5.3 mmol/l.

CONCLUSIONS

While previously neglected as a screening test for GDM, in selected high-risk populations the FPG offers a potentially simple, practical algorithm to screen for GDM by being cost-effective and patient friendly. A wider application should be explored.

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.

Factors affecting fetal weight distribution in women with type I diabetes

OBJECTIVE

To identify factors independently affecting fetal weight in women with type I diabetes.

DESIGN

Prospectively recorded data in consecutive women with type I diabetes, between 1975-1992.

SETTING

Simpson Memorial Maternity Hospital, Edinburgh. Population Three hundred and two pregnancies with type I diabetes identified before pregnancy, with antenatal care and delivery in the Simpson Memorial Maternity Hospital, a singleton pregnancy, and the same diabetic physician.

METHODS

Normal ranges for birthweight were established for the total hospital population. All cases and the total population had pregnancy dating by ultrasound. The relation between standardised birthweight and explanatory variables was investigated using correlation analysis, t tests and chi2 tests as appropriate, and subsequently using multiple linear regression.

RESULTS

Standardised birthweight in cases, compared with the reference population, showed a unimodal, approximately normal distribution, markedly shifted to the right (mean + 1.26 SD). The most predictive variable was glycated haemoglobin concentration at 27-33 weeks, which explained 6.3% of the birthweight variance, while smoking explained 2.7% and maternal weight 2.0%. There was a trend towards a negative relationship with glycated haemoglobin concentration at 6-12 weeks. Smoking and glycated haemoglobin concentration were strongly intercorrelated.

CONCLUSIONS

Most of the variance in standardised birthweight remains unexplained, but glycated haemoglobin concentration at 27-33 weeks is the most powerful explanatory variable. Possible reasons why there is not a stronger relationship between markers of maternal glycaemia and birthweight are discussed.

Is mild gestational hyperglycaemia associated with maternal and neonatal complications? The Diagest Study

AIMS

To evaluate the maternal and neonatal complications rates of mild gestational hyperglycaemia (MGH) compared to a control group in France.

METHODS

A systematic screening by a 50-g glucose challenge test was offered to all women between 24 and 28 weeks of gestation in 15 maternity units. If the 50-g glucose challenge test was > or = 7.2 mmol/l, a 100-g 3-h oral glucose tolerance test (OGTT) was performed. MGH (n = 131) was defined by one abnormal value on the 3-h OGTT (Carpenter and Coustan criteria). The control group (n = 108) was defined by a 50-g glucose challenge test below 7.2 mmol/l. Women with MGH received no treatment or specific advice during the pregnancy. Large for gestational age (LGA) was defined by a birth weight of at least the 90th percentile on French standard growth curves.

RESULTS

Women with MGH were older than the controls (28.8 (5.8) vs. 27.0 (5.2); P < 0.05) and had a higher body mass index (24.8 (4.8) vs. 23.0 (3.9); P < 0.01). The rate of pregnancy-induced hypertension and Caesarean section were not different between the MGH and control group. The rate of LGA was significantly higher in the MGH group than the control group (22.1% vs. 11.4%; P < 0.05). After adjustment for confounding factors of macrosomia (pre-pregnancy body mass index > 27, maternal age > 35, multiparity and educational level), there was a persistent relationship between LGA and MGH (odds ratio 2.50; 95% confidence interval (1.16-5.40); P < 0.05). MGH was more frequently associated with adverse maternal and fetal outcome than in the controls (53.4% vs. 28.7%; P < 0.01).

CONCLUSIONS

This study suggested that the increased rate of adverse maternal and fetal outcome, especially LGA, was associated with untreated mild gestational hyperglycaemia women compared to a control group. This link to lower degrees of hyperglycaemia during pregnancy is independent of confounding factors.

Maternal obesity and glucose intolerance during pregnancy among Mexican-Americans

Low birthweight is uncommon among Mexican-American infants, despite the substantial proportion of mothers who live in poverty. This apparent paradox has generated studies of factors protecting fetal growth, but may have masked other important health problems in the Mexican-American community. Obesity, impaired glucose tolerance and diabetes are common among Mexican-American women of childbearing age and during pregnancy. Prevalence of these conditions is two to four times higher in Mexican-American than in non-Hispanic white women. As obesity and glucose intolerance during pregnancy are associated with fetal overgrowth and increased risk of subsequent obesity and type 2 diabetes in mother and child, the adequacy of birthweight as a measure of maternal and infant risk may be obscured in populations with a high prevalence of these conditions. Their possible contribution to the increasing incidence of obesity and type 2 diabetes in Mexican-American children, adolescents and young adults has not been examined. Appropriate preconception, prenatal and follow-up care may identify high-risk women, improve weight and metabolic status and reduce the severity and impact of diabetes and its complications. However, late or no prenatal care is common among Mexican-American women and the frequency of follow-up care is unknown. As low birthweight is a major public health indicator of maternal and neonatal health, perceived 'good birth outcomes' have reduced health policy, programme and research attention to Mexican-American mothers and infants. Studies of the impact of obesity and glucose intolerance during pregnancy on the birthweights of Mexican-American infants should be undertaken, along with systematic assessment of the subsequent health status and preventive health-care needs of women and children in this population.

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.

Gestational diabetes mellitus: controversies and current opinions

The past few years have seen significant controversy over the diagnosis and management of gestational diabetes and its influence on perinatal outcomes. The debate over who to screen and how to screen continues to rage. Even when a diagnosis has been made, there is a lack of consensus regarding appropriate management protocols and glycemic targets. In this review, we will examine many of the controversial areas in gestational diabetes, using contemporary data to discuss these issues.

Pregnancy in diabetes

For patients with preconception diabetes, the most important aspect is the need for good glycemic control pre conception to lessen the risk of congenital malformations. Careful assessment of diabetes complications is essential prepregnancy. In the absence of major complications, good glycemic control gives the pregnant diabetic patient the same chance for a healthy baby as the rest of the population. Pregnancy alters carbohydrate tolerance, and thus gestational diabetes should be screened for and, when found, treated aggressively with dietary intervention, glucose monitoring, and insulin if good glycemic control has not been attained. These patients are at greatly increased risk for diabetes in the long term.

Screening for gestational diabetes mellitus in adolescent pregnancies

OBJECTIVE

Our purpose was to determine the incidence of gestational diabetes mellitus in an adolescent population and to determine the cost of screening.

STUDY DESIGN

A retrospective review of 509 adolescent pregnancies was performed. The incidence of gestational diabetes mellitus was determined and the cost of screening analyzed.

RESULTS

Five hundred nine adolescent pregnancies were screened for gestational diabetes mellitus with a 1-hour, 50 gm oral glucose challenge test. Twenty-three of the screens (4.5%) had positive results at a plasma glucose level of > or = 140 mg/dl. Three-hour 100 gm oral glucose tolerance tests were performed on screen-positive women, six of whom were diagnosed with gestational diabetes mellitus, for an incidence of 1.18%. The cost per case diagnosed was $2733.

CONCLUSIONS

The incidence of gestational diabetes mellitus in an adolescent population is low. The cost of universal screening may be prohibitive in this population. Large prospective studies are needed to better analyze outcome data and efficacy of screening in adolescent pregnancies.

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.

Diabetes in pregnancy

Women with diabetes in pregnancy can be divided into two groups: women with diabetes diagnosed before pregnancy (pregestational diabetes) and women with glucose intolerance diagnosed during pregnancy (gestational diabetes mellitus). The majority of women with pregestational diabetes have insulin-dependent diabetes mellitus (IDDM), but may also include early-onset non-insulin dependent diabetes mellitus (NIDDM). Gestational diabetes mellitus (GDM) can represent first recognition of IDDM or NIDDM. The expression of each of the forms of diabetes as a clinical disorder represents a complex interaction of genetic and environmental factors. The prevalence of GDM varies between 0.15 and 4% and the prevalence of pre-GDM 0.2-0.4% in European countries [1].

Should the same glucose values be targeted for type 1 as for type 2 diabetics in pregnancy?

OBJECTIVE

Our purpose was to determine whether the same maternal glycemic control is necessary to achieve similar perinatal outcomes for type 1 as for type 2 diabetics.

STUDY DESIGN

The subjects were all women with pregestational diabetes mellitus delivered of live-born singletons. Glycemic control was achieved with diet and insulin. Self-monitoring of blood glucose was performed before meals and at bedtime. Target glucose values were 60 to 90 mg/dl fasting and 60 to 105 mg/dl at other times.

RESULTS

Of 60,628 deliveries, 46 type 1 and 113 type 2 diabetic women met inclusion criteria. Respective differences were found between type 1 and type 2 diabetics in average daily glucose levels (112 mg/dl vs 97 mg/dl, p < 0.001), percent of values within target ranges (35% vs 57%, p < 0.001), and mean amplitude of glycemic excursion (48.1 mg/dl vs 24.9 mg/dl, p < 0.001). At least one daily glucose value was < 50 mg/dl during 19% of observation days for type 1 vs 2% of observation days for type 2 pregnancies (p < 0.001). There were no statistically significant differences between type 1 and type 2 diabetic pregnancies in neonatal macrosomia (30% vs 34%), proportion of cesarean deliveries during labor for arrest disorders (67% vs 69%), shoulder dystocia (2% vs 6%), and neonatal hypoglycemia (18% vs 26%).

CONCLUSIONS

Less stringent maternal glycemic control may permit comparable maternal and neonatal outcomes for type 1 compared with type 2 diabetics. Higher target values for type 1 diabetics may decrease the frequency of maternal hypoglycemic episodes.

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.