Screening and diagnosis of gestational diabetes

Gestational diabetes in twin pregnancies-a pathology requiring treatment or a benign physiological adaptation?

There is level-1 evidence that screening for and treating gestational diabetes in singleton pregnancies reduce maternal and neonatal morbidity. However, similar data for gestational diabetes in twin pregnancies are currently lacking. Consequently, the current approach for the diagnosis and management of gestational diabetes in twin pregnancies is based on the same diagnostic criteria and glycemic targets used in singleton pregnancies. However, twin pregnancies have unique physiological characteristics, and many of the typical gestational diabetes-related complications are less relevant for twin pregnancies. These differences raise the question of whether the greater increase in insulin resistance observed in twin pregnancies (which is often diagnosed as diet-treated gestational diabetes) should be considered physiological and potentially beneficial in which case alternative criteria should be used for the diagnosis of gestational diabetes in twin pregnancies. In this review, we summarize the most up-to-date evidence on the epidemiology, pathophysiology, and clinical consequences of gestational diabetes in twin pregnancies and review the available data on twin-specific screening and diagnostic criteria for gestational diabetes. Although twin pregnancies are associated with a higher incidence of diet-treated gestational diabetes, diet-treated gestational diabetes in twin pregnancies is less likely to be associated with adverse outcomes and accelerated fetal growth than in singleton pregnancies and may reduce the risk for intrauterine growth restriction. In addition, there is currently no evidence that treatment of diet-treated gestational diabetes in twin pregnancies improves outcomes, whereas preliminary data suggest that strict glycemic control in such cases might increase the risk for intrauterine growth restriction. Overall, these findings provide support to the hypothesis that the greater transient increase in insulin resistance observed in twin pregnancies is merely a physiological exaggeration of the normal increase in insulin resistance observed in singleton pregnancies (that is meant to support 2 fetuses) rather than a pathology that requires treatment. These data illustrate the need to develop twin-specific screening and diagnostic criteria for gestational diabetes to avoid overdiagnosis of gestational diabetes and to reduce the risks associated with overtreatment of diet-treated gestational diabetes in twin pregnancies. Although data on twin-specific screening and diagnostic criteria are presently scarce, preliminary data suggest that the optimal screening and diagnostic criteria in twin pregnancies are higher than those currently used in singleton pregnancies.

DEVELOPING twin-specific 75-g oral glucose tolerance test diagnostic thresholds for gestational diabetes based on the risk of future maternal diabetes: a population-based cohort study

OBJECTIVE

To develop twin-specific outcome-based oral glucose tolerance test (OGTT) diagnostic thresholds for GDM based on the risk of future maternal type-2 diabetes.

DESIGN

A population-based retrospective cohort study (2007-2017).

SETTING

Ontario, Canada.

METHODS

Nulliparous women with a live singleton (n = 55 361) or twin (n = 1308) birth who underwent testing for gestational diabetes mellitus (GDM) using a 75-g OGTT in Ontario, Canada (2007-2017). We identified the 75-g OGTT thresholds in twin pregnancies that were associated with similar incidence rates of future type-2 diabetes to those associated with the standard OGTT thresholds in singleton pregnancies.

RESULTS

For any given 75-g OGTT value, the incidence rate of future maternal type-2 diabetes was lower for women with a twin than women with a singleton pregnancy. Using women with a negative OGTT as reference, the risk of future maternal type-2 diabetes in twin pregnancies with a positive OGTT based on the standard OGTT thresholds (9.86 per 1000 person years, adjusted hazard ratio (aHR) 4.79, 95% CI 2.69-8.51) was lower than for singleton pregnancies with a positive OGTT (18.74 per 1000 person years, aHR 8.22, 95% CI 7.38-9.16). The twin-specific OGTT fasting, 1-hour and 2-hour thresholds identified in the current study based on correlation with future maternal type-2 diabetes were 5.8 mmol/l (104 mg/dl), 11.8 mmol/l (213 mg/dl) and 10.4 mmol/l (187 mg/dl), respectively.

CONCLUSIONS

We identified potential twin-specific OGTT thresholds for GDM that are associated with a similar risk of future type-2 diabetes to that observed in women diagnosed with GDM in singleton pregnancies based on standard OGTT thresholds.

TWEETABLE ABSTRACT

Potential twin-specific OGTT thresholds for GDM were identified.

Assessment of insulin sensitivity/resistance and their relations with leptin concentrations and anthropometric measures in a pregnant population with and without gestational diabetes mellitus

Fifty-six pregnant women with gestational diabetes mellitus (GDM) and 42 normal glucose tolerant (NGT) pregnant women between 26 and 36 gestational weeks were included in the study prospectively. The body fat percentage (BFP) was calculated using the Siri formula from skinfold thickness (SFT) measurements. Both groups were comparable for gestational age, height, weight, and body mass index (P>.05). Insulin resistance assessed by homeostasis model assessment for insulin resistance (HOMA-IR) method was significantly higher in GDM patients compared to their NGT weight-matched control group. In contrast, the insulin sensitivity calculated from quantitative insulin sensitivity check index (QUICKI-IS) equation was significantly lower in GDM group. Calculated lean body mass was found to be similar in between both groups. Body fat percentage derived from SFT parameters was significantly higher in women with GDM. Women with GDM had significantly higher levels of serum insulin and leptin concentrations when compared with the NGT group. All SFT measurements were higher in GDM group when compared to those in NGT women. We did not find any correlation between leptin levels and insulin resistance; we found negative correlation between leptin levels and insulin sensitivity. Thus, we observed that leptin may contribute development of GDM by decreasing insulin sensitivity but not increasing insulin resistance. Also, we observed that the BFP estimated by the Siri formula from SFT measurements correlated significantly with HOMA-IR and QUICKI-IS and leptin concentrations in pregnant women. We suggest that by simply evaluating SFT, we may hold a view about BFP and leptin concentrations and insulin sensitivity in pregnant women.

Placental weight and placental weight-to-birth weight ratio are increased in diet- and exercise-treated gestational diabetes mellitus subjects but not in subjects with one abnormal value on 100-g oral glucose tolerance test

The aim of the present study was to determine whether the placental weight and placental weight-to-birth weight ratio (PW/BW) increased in pregnant women with one abnormal value (OAV) on 100-g oral glucose tolerance test (OGTT) and diet- and exercise-treated, non-insulin-requiring gestational diabetes mellitus (GDM) subjects. The 50-g glucose challenge test (GCT) was administered to 324 pregnant women. Women with abnormal 50-g test received a 100-g, 3-h OGTT using National Diabetes Data Group criteria. Women with GDM and OAV were treated with diet and exercise. Twenty subjects who required insulin or met exclusion criteria were excluded from the study. After the exclusion of 20 subjects, the GDM group consisted of 30 (9.7%) pregnant women and the OAV group consisted of 32 (9.9%) pregnant women. The control group consisted of 242 pregnant women. Birth weight (GDM: 3288.3+/-364.2 g; OAV: 3278.1+/-409.9 g; control group: 3270.6+/-346.5 g) did not differ significantly between groups (P>.05). Significantly higher placental weights (GDM: 694.8+/-152.1 g; OAV: 622.2+/-105.3 g; control group: 610.2+/-116.6 g; P<.01) and PW/BW (GDM: 0.21+/-0.03; OAV: 0.193+/-0.04; control group: 0.188+/-0.04; P<.01) were observed in GDM group compared to OAV and control group. No significant difference was found for OAV group in terms of placental weight and PW/BW compared to the control group. Our data indicated that women with OAV delivered infants and placenta of similar weight to those of normal pregnancies.

The 75-gram glucose load in pregnancy: relation between glucose levels and anthropometric characteristics of infants born to women with normal glucose metabolism

OBJECTIVE

To investigate, in pregnant women without gestational diabetes mellitus (GDM), the relation among obstetric/demographic characteristics; fasting, 1-h, and 2-h plasma glucose values resulting from a 75-g glucose load; and the risk of abnormal neonatal anthropometric features and then to verify the presence of a threshold glucose value for a 75-g glucose load above which there is an increased risk for abnormal neonatal anthropometric characteristics.

RESEARCH DESIGN AND METHODS

The study group consisted of 829 Caucasian pregnant women with singleton pregnancy who had no history of pregestational diabetes or GDM, who were tested for GDM with a 75-g, 2-h glucose load, used as a glucose challenge test, in two periods of pregnancy (early, 16-20 weeks; late, 26-30 weeks), and who did not meet the criteria for a GDM diagnosis. In the newborns, the following abnormal anthropometric characteristics were considered as outcome measures: cranial/thoracic circumference (CC/TC) ratio </=10th percentile for gestational age (GA), ponderal index (birth weight/length(3) x 100) >/=90th percentile for GA, and macrosomia (birth weight >/=90th percentile for GA), on the basis of growth standard development for our population. For the first part of the objective, logistic regression models were used to identify 75-g glucose load values as well as obstetric and demographic variables as markers for abnormal neonatal anthropometric characteristics. For the second part, the receiver operating characteristic (ROC) curve was performed for the 75-g glucose load values to determine the plasma glucose threshold value that yielded the highest combined sensitivity and specificity for the prediction of abnormal neonatal anthropometric characteristics.

RESULTS

In both early and late periods, maternal age >35 years was a predictor of neonatal CC/TC ratio </=10th percentile and macrosomia, with fasting 75-g glucose load values being independent predictors of neonatal CC/TC ratio </=10th percentile. In both periods, 1-h values gave a strong association with all abnormal neonatal anthropometric characteristics chosen as outcome measures, with maternal age >35 years being an independent predictor for macrosomia. The 2-h, 75-g glucose load values were significantly associated in both periods with neonatal CC/TC ratio </=10th percentile and ponderal index >/=90th percentile, whereas maternal age >35 years was an independent predictor of both neonatal CC/TC ratio </=10th percentile and macrosomia. In the ROC curves for the prediction of neonatal CC/TC ratio </=10th percentile for GA in both early and late periods of pregnancy, inflection points were identified for a 1-h, 75-g glucose load threshold value of 150 mg/dl in the early period and 160 mg/dl in the late period.

CONCLUSIONS

This study documented a significant association, seen even in the early period of pregnancy, between 1-h, 75-g glucose load values and abnormal neonatal anthropometric features, and provided evidence of a threshold relation between 75-g glucose load results and clinical outcome. Our results would therefore suggest the possibility of using a 75-g, 1-h oral glucose load as a single test for the diagnosis of GDM, adopting a threshold value of 150 mg/dl at 16-20 weeks and 160 mg/dl at 26-30 weeks.

Postpartum oral glucose tolerance tests in mothers of macarosomic infants: inadequacy of current antenatal test criteria in detecting prediabetic state

OBJECTIVE

To assess the presence of subtle carbohydrate metabolism abnormalities in otherwise healthy mothers who have given macrosomic birth by utilizing postpartum oral glucose tolerance test (PPOGTT).

STUDY DESIGN

Prospective controlled study enrolled gestational diabetic women (GDM, n=10), mothers with macrosomic infants (MwMIs, n=62) and controls (n=50).

RESULTS

Receiver operating characteristic (ROC) curve analysis revealed that incremental 1-h+2-h PPOGTT value >111 mg/dl had a sensitivity of 80% and specificity of 78% in predicting antecedent diabetes. PPOGTT results were positive in 53.2% of MwMIs and 28% of controls (P<0.01). Maternal low-density lipoprotein and triglyceride levels, 50 gram glucose challenge test (50 g GCT) values and neonatal weight were the significant predictors of PPOGTT results. ROC analyses suggested that threshold of 50 g GCT should be lowered in order to better predict subjects with both macrosomia and positive PPOGTT.

CONCLUSION

PPOGTT may identify a subset of women with macrosomic infants who have metabolic alterations of a prediabetic state. The discrepancies between antenatal and postpartum tests may reflect the need for redefinition of currently utilized criteria in screening and diagnosis of GDM.

Decrease in incidence of gestational diabetes mellitus in Far North Queensland between 1992 and 1996

The pregnant population in Far North Queensland is at high risk of medical complications, such as diabetes, compared to the general Australian population (1,2). This retrospective observational study shows a true decline in the incidence of gestational diabetes mellitus (GDM) in this region over a 5-year period (1992-1996), contradicting the current belief that the incidence of GDM is increasing in non-Caucasian Australians. Although this change may be due to an improvement in medical and/or dietary intervention in this region, the real cause for the decline is yet to be recognized.

Time-dependent gestational diabetes screening values

OBJECTIVE

This study was undertaken to determine use of different cut-off values with regard to the time of the patient's last meal in screening for gestational diabetes mellitus which could result in better results and change patient management.

METHODS

Two hundred and seventy-four non-diabetic women undergoing routine screening for glucose intolerance between 26 to 28 weeks' gestation were classified with regard to the time of previous meal. A glucose challenge test and an oral glucose challenge test were conducted for each patient in the study. Results were evaluated with both a standard cut-off value of 140 mg/dl without regard to the time of the last meal and suggested cut-off values of 148 mg/dl, 142 mg/dl, and 150 mg/dl if the patient ate < 2 h, 2-3 h, and > 3 h before the screening test, respectively.

RESULTS

Two hundred and seventy-four women completed the study. With these suggested cut-off values, the number of patients with a positive glucose challenge test dropped from 15.7% to 11.3%. With these cut-off values, positive predictive value increased from 27.3% to 32.3%.

CONCLUSIONS

The time since previous meal affects 50 g glucose challenge test results. These new cut-off values would lead to improved efficiency of the screening test and decreased frequency with which patients require the 3-h oral glucose tolerance test.

Nutrition management in women with gestational diabetes mellitus: a review by ADA's Diabetes Care and Education Dietetic Practice Group

Gestational diabetes mellitus (GDM) is the most common medical disorder complicating pregnancy that requires the services of a registered dietitian. Despite three international workshops on GDM, many questions remain regarding its epidemiology, pathophysiology, screening, diagnosis, and management. Registered dietitians encounter these controversial issues when working with women referred for GDM education and counseling. Nutrition intervention remains the cornerstone of therapy. The purpose of this article is not to provide practice guidelines but to review the literature and current practices in research centers across the United States. Registered dietitians are in a position to individualize nutrition care to each woman's needs and to participate in the decision-making process of nutrition management.