Gestational Diabetes Mellitus: Is It Time to Reconsider the Diagnostic Criteria?

Establishing novel diagnostic criteria for the glucose tolerance test for the diagnosis of gestational diabetes and gestational hyperglycemia

OBJECTIVE

To establish diagnostic criteria for the 75-g 2-h glucose tolerance test (GTT) to diagnose gestational diabetes and define the clinical entity of gestational hyperglycemia.

METHODS

A retrospective analysis was performed of the results from 500 patients who had a 75-g 1-h glucose challenge test (GCT) in early pregnancy as part of a two-step approach to screening and testing for gestational diabetes. The selected cohort was considered to have normal islet β-cell function, and upper glycemic levels of normal glucose tolerance in the third trimester were statistically calculated, taking the cutoff threshold values to be the diagnostic criteria for the 75-g 2-h GTT. Gestational hyperglycemia was diagnosed from the false-positive GCT result when ≥8.0 mmol/L (144 mg/dL).

RESULTS

The diagnostic criteria for the 75-g 2-h GTT were calculated as follows: fasting plasma glucose ≥5.4 mmol/L (97 mg/dL); 1-h plasma glucose ≥10.5 mmol/L (189 mg/dL); and 2-h plasma glucose ≥8.4 mmol/L (151 mg/dL). The new criteria confirmed a prevalence of gestational diabetes of 11.1% and gestational hyperglycemia of 13.6% in the study population.

CONCLUSION

Novel diagnostic criteria for the 75-g 2-h GTT were established by statistical analysis. This resulted in a more acceptable prevalence of gestational diabetes in our community and the false-positive GCT allowed the detection of gestational hyperglycemia.

Maternal and fetal outcomes of pregnancies associated with single versus double abnormal values in 100 gr glucose tolerance test

Purpose of the study

Comparing maternal and fetal outcomes in pregnancies associated with single versus double abnormal values in 100 gr oral glucose tolerance test (OGTT).

Methods

This cohort study was performed in Arash women's Hospital, Tehran, Iran from 2019 to 2020. Patients with normal fasting blood sugar (FBS) tests were divided into two groups according to their OGTT results. The first group had a single abnormal value in their OGTT and the second group showed two abnormal values. Both groups were followed regularly until the end of pregnancy.

Results

Our results showed higher rates of macrosomia (birth of newborns weighed over 4 kg) and the need for pharmacological treatment for the management of GDM in the second group (P = 0.05). There were no differences between the two groups in terms of other maternal (polyhydramnios, shoulder dystocia, operative vaginal delivery, atony, postpartum bleeding, cesarean delivery, preeclampsia, and IUFD) and fetal outcomes (Apgar score, seizure, NICU admission, and hypoglycemia in the first 24 h).

Conclusion

We found no significant differences between pregnant women with single and double abnormal values in 100 gr OGTT regarding maternal and neonatal outcomes, except for macrosomia and need for pharmaceutical treatment.

Comparing IADPSG and NICE Diagnostic Criteria for GDM in Predicting Adverse Pregnancy Outcomes

OBJECTIVE

To compare the performance of diagnostic criteria for gestational diabetes mellitus (GDM) proposed by the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) with those endorsed by the National Institute for Health and Care Excellence (NICE) in predicting adverse pregnancy outcomes.

RESEARCH DESIGN AND METHODS

We performed a secondary data analysis of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study participants in five study centers. Logistic regression analyses were performed, and Akaike information criterion were applied for the comparison of different statistical prediction models. We further analyzed the performance by four racial/ethnic subgroups, namely, Whites, Hispanics, Asians, and Blacks.

RESULTS

Among all, IADPSG criteria diagnosed 267 (4.1%) more women with GDM, but predicted primary caesarean section (CS) and large for gestational age (LGA) and neonatal adiposity better than did NICE criteria after adjustment for potential confounders. Among Whites, IADPSG criteria diagnosed 65 (2.5%) more subjects with GDM and predicted LGA and neonatal adiposity better, but predicted hypertensive disorders, primary CS and clinical neonatal hypoglycemia worse. Among Hispanics, the IADPSG criteria diagnosed 203 (12.1%) more with GDM but performed better in predicting hypertensive disorders, LGA, neonatal adiposity, and hyperinsulinemia. Among Asians, the IADPSG criteria diagnosed 34 (2.0%) fewer subjects with GDM but predicted hypertensive disorders better in the unadjusted model. In Blacks, IADPSG criteria diagnosed 34 (10.5%) more women with GDM.

CONCLUSIONS

IADPSG criteria appear to be more favorable than NICE for identification of adverse pregnancy outcomes among Hispanic and Asian women, while they are comparable to NICE among White women.

Screening for Gestational Diabetes Mellitus and Pregnancy Outcomes: Results from a Multicentric Study in Tajikistan

The prevalence of gestational diabetes parallels the prevalence of type 2 diabetes mellitus and is associated with adverse pregnancy outcomes. However, these data are not available for many parts of the world. We assessed the prevalence of gestational diabetes and pregnancy outcomes in Tajikistan. This cohort study included 2438 consecutively recruited representative pregnant women from 8 locations in two cities in Tajikistan, in whom an oral glucose tolerance test (75 g, fasting, 1 h, 2 h) was performed during gestational weeks 24-28. Women with known diabetes and twin pregnancies were excluded. Associations between glucose tolerance test results and pregnancy outcomes were examined. According to the WHO 2013 thresholds, 32.4% of women qualified as having gestational diabetes, the vast majority (29.7%) based on an elevated fasting glucose level (5.1-5.6 mmol/L), while only 2.8% had elevated 1- or 2-hour values or met more than one threshold. Women with only elevated fasting glucose (impaired gestational fasting glycemia) had no evidence of adverse pregnancy outcomes, while those with elevated 1- and/or 2-hour values (impaired gestational glucose tolerance) had more pregnancy complications (infection of urinary tract 1.8 vs. 8.8% p<0.001; preeclampsia 0.7 vs. 10.3% p<0.001) and emergency cesarean sections (4.4 vs. 13.2% p=0.002). Neonates from pregnancies with impaired gestational glucose tolerance had lower APGARs, lower birth weights, lower 30 min glucose levels, and a lower probability of being discharged alive (all p<0.05). In conclusion, the formal prevalence of gestational diabetes is high in Tajikistan; however, this does not translate into adverse pregnancy outcomes for women with impaired gestational fasting glycemia.

Pragmatic trials can address diagnostic controversies: recent lessons from gestational diabetes

Objective

The aim of the paper is to discuss how a pragmatic definition could change our conception of diagnosis, using gestational diabetes mellitus (GDM) as an example.

Study design

We review the diagnostic controversy that followed an observational study showing a linear relationship between maternal glycaemia and adverse pregnancy outcomes and the resolution proposed 15 years later by a recent pragmatic trial comparing two screening approaches (one- vs two-step) with different diagnostic thresholds.

Results

The pragmatic trial involved approximately 24,000 women. The one-step screening strategy using lower GDM thresholds diagnosed twice as many women with GDM, but pregnancy outcomes were not different. We examine how the pragmatic approach integrates research into practice and defines the meaning of a diagnosis according to patient outcomes. The approach is ethically and scientifically sound as compared to the previous methodology, where observational research separated from care gave a theoretical definition of GDM that may have misled medical practice for two decades.

Conclusion

Pragmatic research integrated into practice can revolutionize our conception of medical diagnosis in the best medical interest of patients.

Glycated albumin in pregnancy: LC-MS/MS-based reference interval in healthy, nulliparous Scandinavian women and its diagnostic accuracy in gestational diabetes mellitus

Glycated albumin (GA) may be a useful biomarker of glycemia in pregnancy. The aim of this study was to establish the reference interval (RI) for GA, analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), in healthy, nulliparous pregnant women. In addition, we assessed the accuracy of GA and glycated hemoglobin A1c (HbA1c) in the diagnosis of gestational diabetes mellitus (GDM). Finally, we explored the prevalence of GDM in healthy nulliparas, comparing three diagnostic guidelines (WHO-1999, WHO-2013 and the Norwegian guideline). The study was carried out at Stavanger University Hospital, Norway, and included a study population of 147 pregnant nulliparous women. An oral glucose tolerance test (OGTT) was performed and used as the gold standard for GDM diagnosis. Blood samples for analysis of GA and HbA1c were collected at pregnancy week 24-28. A nonparametric approach was chosen for RI calculation, and receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance of GA and HbA1c. The established RI for GA in 121 pregnant women was 7.1-11.6%. The area under the ROC curves (AUCs) were 0.531 (GA) and 0.627 (HbA1c). According to the WHO-1999, WHO-2013 and the Norwegian guideline, respectively, 24 (16%), 36 (24%) and 21 (14%) women were diagnosed with GDM. Only nine women (6%) fulfilled the GDM-criteria of all guidelines. In conclusion, we established the first LC-MS/MS-based RI for GA in pregnant women. At pregnancy weeks 24-28, neither GA nor HbA1c discriminated between those with and without GDM. Different women were diagnosed with GDM using the three guidelines.

Gestational Diabetes Mellitus in Europe: A Systematic Review and Meta-Analysis of Prevalence Studies

Background

Gestational Diabetes Mellitus (GDM) is defined as the type of hyperglycemia diagnosed for the first-time during pregnancy, presenting with intermediate glucose levels between normal levels for pregnancy and glucose levels diagnostic of diabetes in the non-pregnant state. We aimed to systematically review and meta-analyze studies of prevalence of GDM in European countries at regional and sub-regional levels, according to age, trimester, body weight, and GDM diagnostic criteria.

Methods

Systematic search was conducted in five databases to retrieve studies from 2014 to 2019 reporting the prevalence of GDM in Europe. Two authors have independently screened titles and abstracts and full text according to eligibility using Covidence software. A random-effects model was used to quantify weighted GDM prevalence estimates. The National Heart, Lung, and Blood Institute criteria was used to assess the risk of bias.

Results

From the searched databases, 133 research reports were deemed eligible and included in the meta-analysis. The research reports yielded 254 GDM-prevalence studies that tested 15,572,847 pregnant women between 2014 and 2019. The 133 research reports were from 24 countries in Northern Europe (44.4%), Southern Europe (27.1%), Western Europe (24.1%), and Eastern Europe (4.5%). The overall weighted GDM prevalence in the 24 European countries was estimated at 10.9% (95% CI: 10.0-11.8, I2 : 100%). The weighted GDM prevalence was highest in the Eastern Europe (31.5%, 95% CI: 19.8-44.6, I2 : 98.9%), followed by in Southern Europe (12.3%, 95% CI: 10.9-13.9, I2 : 99.6%), Western Europe (10.7%, 95% CI: 9.5-12.0, I2 : 99.9%), and Northern Europe (8.9%, 95% CI: 7.9-10.0, I2 : 100). GDM prevalence was 2.14-fold increased in pregnant women with maternal age ≥30 years (versus 15-29 years old), 1.47-fold if the diagnosis was made in the third trimester (versus second trimester), and 6.79- fold in obese and 2.29-fold in overweight women (versus normal weight).

Conclusions

In Europe, GDM is significant in pregnant women, around 11%, with the highest prevalence in pregnant women of Eastern European countries (31.5%). Findings have implications to guide vigilant public health awareness campaigns about the risk factors associated with developing GDM.

Systematic Review Registration

PROSPERO [https://www.crd.york.ac.uk/PROSPERO/], identifier CRD42020161857.

The screening performance of glucose challenge test for gestational diabetes in twin pregnancies: a systematic review and meta-analysis

BACKGROUND

The screening accuracy of the 50 g-glucose challenge test (50 g-GCT) for gestational diabetes (GDM) has been described in singleton pregnancies. Given the physiologic differences and greater increase in insulin resistance in twin compared with singleton pregnancies, the performance of the 50 g-GCT in twin pregnancies may differ.

OBJECTIVES

To perform a systematic review on the screening performance of the 50 g-GCT for gestational diabetes in twin pregnancies.

DATA SOURCES

Ovid Medline, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL).

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS

We included randomized controlled trials or cohort studies that evaluated the screening accuracy of the 50 g-GCT for GDM in twin pregnancies using the two-step approach. The primary outcome was the positive predictive value of the 50 g-GCT for GDM using the 140 mg/dL (7.8 mmol/L) threshold.

STUDY APPRAISAL AND SYNTHESIS METHODS

Methodological quality of included studies was assessed using the QUADAS-2 tool. The positive predictive value (PPV) was pooled for studies that used similar test characteristics.

RESULTS

From 2044 citations, 7 retrospective cohort studies with a total of 55,597 participants were included (6.5% twins and 93.5% singletons). The majority of studies evaluated a 50-g GCT cutoff point of 140 mg/dL. The pooled PPV for a threshold of 140 mg/dL (7.8 mmol/L) for twins was 22.58% (95% CI: 0.1912-0.2647, I²=34.1%). The 50-g GCT screen positive rate in twin pregnancies was higher than that in singleton pregnancies. None of the studies performed routine OGTT.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

The PPV of 50 g-GCT for GDM in twin pregnancies when using a threshold of 140 mg/dL (7.8 mmol/L) is approximately 23%. There is currently no data on the sensitivity and specificity of the 50 g-GCT in twins.

Estimated impact of introduction of new diagnostic criteria for gestational diabetes mellitus

BACKGROUND

Implementation of new diagnostic criteria for gestational diabetes mellitus (GDM) are still a subject of debate, mostly due to concerns regarding the effects on the number of women diagnosed with GDM and the risk profile of the women newly diagnosed.

AIM

To estimate the impact of the World Health Organization (WHO) 2013 criteria compared with the WHO 1999 criteria on the incidence of gestational diabetes mellitus as well as to determine the diagnostic accuracy for detecting adverse pregnancy outcomes.

METHODS

We retrospectively analyzed a single center Dutch cohort of 3338 women undergoing a 75 g oral glucose tolerance test where the WHO 1999 criteria to diagnose GDM were clinically applied. Women were categorized into four groups: non-GDM by both criteria, GDM by WHO 1999 only (excluded from GDM), GDM by WHO 2013 only (newly diagnosed) and GDM by both criteria. We compared maternal characteristics, pregnancy outcomes and likelihood ratios for adverse pregnancy outcomes.

RESULTS

Retrospectively applying the WHO 2013 criteria increased the cohort incidence by 13.1%, from 19.3% to 32.4%. Discordant diagnoses occurred in 21.3%; 4.1% would no longer be labelled as GDM, and 17.2% were newly diagnosed. Compared to the non-GDM group, women newly diagnosed were older, had higher rates of obesity, higher diastolic blood pressure and higher rates of caesarean deliveries. Their infants were more often delivered preterm, large-for-gestational-age and were at higher risk of a 5 min Apgar score < 7. Women excluded from GDM were older and had similar pregnancy outcomes compared to the non-GDM group, except for higher rates of shoulder dystocia (4.3% vs 1.3%, P = 0.015). Positive likelihood ratios for adverse outcomes in all groups were generally low, ranging from 0.54 to 2.95.

CONCLUSION

Applying the WHO 2013 criteria would result in a substantial increase in GDM diagnoses. Newly diagnosed women are at increased risk for pregnancy adverse outcomes. This risk, however, seems to be lower than those identified by the WHO 1999 criteria. This could potentially influence the treatment effect that can be achieved in this group. Evidence on treatment effects in newly diagnosed women is urgently needed.

Decolonizing Care at Diagnosis: Culture, History, and Family at an Urban Inter-tribal Clinic

The decolonization framework in medical anthropology is slowly reframing tropes of cultural competency toward decolonizing health care. For decolonization of health care to occur, both colonial histories and continuing postcolonial inequities must be recognized from the first diagnostic moment. We report on qualitative research into the role of culture, history, and family experience in person-specific reactions to receipt of a diagnosis. A collaborative approach at an urban inter-tribal clinic was used to interview patients with a recent (within six months) diagnosis of diabetes or related condition. Interviews revealed ways that the Relocation Act eventuated in isolation, poverty, and diabetes among now-urban Native Americans. We discuss how patients may or may not have the ability to (re)connect with their heritage and may simultaneously perceive only recent family contexts as influential in their diabetes. We conclude by acknowledging how postcolonial harms are not captured in diagnoses but should not be left out of diagnostic discussions.

Effect of the IADPSG screening strategy for gestational diabetes on perinatal outcomes in Switzerland

AIMS

To evaluate the impact adoption of the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria on prevalence of gestational diabetes mellitus (GDM) and risks of perinatal outcomes.

METHODS

Retrospectively, 155,103 women screened with selective two step criteria in Switzerland in period 1 (2005-2010) were compared to 170,427 women screened with IADPSG criteria in period 2 (2012-2017). GDM prevalence over time was established and multivariable regression used to assess variation in risks for GDM related events and perinatal outcomes.

RESULTS

GDM prevalence increased steadily over both study periods from 1.8% to 9.0%. A risk reduction of GDM-related events was shown only for women with one or two risk factors for GDM present (relative risk (95% confidence interval)): (0.93 (0.90,0.97), 0.90 (0.83,0.96)). The comparison of perinatal outcomes between the two study periods revealed a significant lower risk for newborns large for gestational age (LGA) (0.93 (0.91-0.95)), pre-term delivery (0.94 (0.92-0.97)) and neonatal hypoglycemia (0.83 (0.77-0.90)) in period 2.

CONCLUSION

The introduction of the IADPSG criteria for the screening of GDM increased prevalence by threefold with no substantial improvements in GDM related events for women without risk factors but reduced the risks for LGA, neonatal hypoglycemia and preterm birth.

Using space-time cube to analyze trends in adverse birth outcomes and maternal characteristics in Massachusetts, USA

Rates of preterm births (< 37 gestational weeks) and low birthweight (≤  2500 g) are rising throughout the United States. This study uses singleton live birth data, Empirical Bayes approach, space-time cube and Mann-Kendall statistic to evaluate temporal trends in these adverse birth outcomes (ABO) and maternal characteristics over 15 years (2000-2014) at the census tract level for non-Hispanic white and black women in Massachusetts. In addition to analyzing trends for each variable individually, the study analyzes spatial coincidence of trends to determine which maternal characteristics exhibited trends that most strongly correlated with the ABO trends. The 15-year average rate of ABO was 7.34% for white women, and 12.05% for black women. Results show that more census tracts exhibited an increasing trend than decreasing trend in birth outcomes and in several maternal characteristics for both races (gestational and chronic hypertension, gestational diabetes, and previous preterm birth). Study identified 52 census tracts concurrently experiencing an increasing trend in ABO and in four maternal characteristics for black women, indicating that multiple negative trends in health outcomes are concentrated at the same location creating a potential for even more adverse outcomes in the future. This study provides a novel, spatially explicit analytical framework based on Empirical Bayes rates and space-time cube, which could be extended to analyze trends in other health outcomes at various spatial scales.

SUPPLEMENTARY INFORMATION

The online version supplementary material available at 10.1007/s10708-021-10382-w.

An Update of Medical Nutrition Therapy in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a serious and frequent pregnancy complication that can lead to short and long-term risks for both mother and fetus. Different health organizations proposed different algorithms for the screening, diagnosis, and management of GDM. Medical Nutrition Therapy (MNT), together with physical exercise and frequent self-monitoring, represents the milestone for GDM treatment in order to reduce maternal and fetal complications. The pregnant woman should benefit from her family support and make changes in their lifestyles, changes that, in the end, will be beneficial for the whole family. The aim of this manuscript is to review the literature about the Medical Nutrition Therapy in GDM and its crucial role in GDM management.

Dysglycemia in Pregnancy and Maternal/Fetal Outcomes

Maternal dysglycemia-including diabetes, impaired glucose tolerance, and impaired fasting glucose-affects one in six pregnancies worldwide and represents a significant health risk to the mother and the fetus. Maternal dysglycemia is an independent risk factor for perinatal mortality, major congenital anomalies, and miscarriages. Furthermore, it increases the longer-term risk of type 2 diabetes mellitus, metabolic syndrome, cardiovascular morbidity, malignancies, and ophthalmic, psychiatric, and renal diseases in the mother. The most commonly encountered form of maternal dysglycemia is gestational diabetes. Currently, international consensus does not exist for diagnostic criteria defining gestational diabetes at 24-28 weeks gestation, and potential diagnostic glucose thresholds earlier in gestation require further investigation. Likewise, recommendations regarding the timing and modality (e.g., lifestyle or pharmacological) of treatment vary greatly. Because a precise diagnosis determines the appropriate treatment and outcome of the pregnancy, it is imperative that a better definition of maternal dysglycemia and its treatment be achieved. This article will address some of the controversies related to diagnosing and managing maternal dysglycemia. In addition, the article will discuss the impact of maternal dysglycemia on complications experienced by the mother and infant, both at birth and in later life.

Effects of Changing Diagnostic Criteria for Gestational Diabetes Mellitus in Queensland, Australia

OBJECTIVE

To evaluate the effects of updated gestational diabetes mellitus (GDM) screening and diagnostic criteria on selected perinatal outcomes in Queensland, Australia.

METHODS

This was a pre-post comparison study using perinatal data the year before (2014) and after (2016) the screening and diagnostic criteria for GDM was changed in Queensland, Australia. In 2015, Queensland adopted the one-step screening and diagnostic criteria based on the International Association of the Diabetes and Pregnancy Study Groups' recommendations. The data from 62,517 women in 2014 and 61,600 women in 2016 who gave birth from 24 weeks of gestation were analyzed in three groups in each year: women with GDM; women without diagnosed GDM; and total population. The outcome measures were gestational hypertension, cesarean birth, gestational age at delivery, birth weight, preterm delivery, large-for-gestational age (LGA) neonates, small-for-gestational-age (SGA) neonates, neonatal hypoglycemia, and respiratory distress.

RESULTS

The diagnosis of GDM increased from 8.7% (n=5,462) to 11.9% (n=7,317). After changing the diagnostic criteria, the changes to outcomes, odds ratios (OR), and adjusted odds ratios (aOR) (95% CI) for outcomes with statistically significant differences for the total population were: gestational hypertension 4.6% vs 5.0%, OR 1.09 (1.03-1.15), aOR 1.07 (1.02-1.13); preterm birth 7.6% vs 8.0%, OR 1.05 (1.01-1.09), aOR 1.06 (1.02-1.10); neonatal hypoglycemia 5.3% vs 6.8%, OR 1.31 (1.25-1.37), aOR 1.32 (1.25-1.38); and respiratory distress 6.2% vs 6.0%, OR 0.96 (0.91-1.00), aOR 0.94 (0.89-0.99). There was no change to cesarean births or LGA or SGA neonates for women with or without diagnosed GDM or the total population.

CONCLUSION

Except for a very small decrease in respiratory distress, changing the diagnostic criteria has resulted in more GDM diagnoses with no observed changes to measured perinatal outcomes for women with and without diagnosed GDM.

Interventions to prevent women from developing gestational diabetes mellitus: an overview of Cochrane Reviews

BACKGROUND

The prevalence of gestational diabetes mellitus (GDM) is increasing, with approximately 15% of pregnant women affected worldwide, varying by country, ethnicity and diagnostic thresholds. There are associated short- and long-term health risks for women and their babies.

OBJECTIVES

We aimed to summarise the evidence from Cochrane systematic reviews on the effects of interventions for preventing GDM.

METHODS

We searched the Cochrane Database of Systematic Reviews (6 August 2019) with key words 'gestational diabetes' OR 'GDM' to identify reviews pre-specifying GDM as an outcome. We included reviews of interventions in women who were pregnant or planning a pregnancy, irrespective of their GDM risk status. Two overview authors independently assessed eligibility, extracted data and assessed quality of evidence using ROBIS and GRADE tools. We assigned interventions to categories with graphic icons to classify the effectiveness of interventions as: clear evidence of benefit or harm (GRADE moderate- or high-quality evidence with a confidence interval (CI) that did not cross the line of no effect); clear evidence of no effect or equivalence (GRADE moderate- or high-quality evidence with a narrow CI crossing the line of no effect); possible benefit or harm (low-quality evidence with a CI that did not cross the line of no effect or GRADE moderate- or high-quality evidence with a wide CI); or unknown benefit or harm (GRADE low-quality evidence with a wide CI or very low-quality evidence).

MAIN RESULTS

We included 11 Cochrane Reviews (71 trials, 23,154 women) with data on GDM. Nine additional reviews pre-specified GDM as an outcome, but did not identify GDM data in included trials. Ten of the 11 reviews were judged to be at low risk of bias and one review at unclear risk of bias. Interventions assessed included diet, exercise, a combination of diet and exercise, dietary supplements, pharmaceuticals, and management of other health problems in pregnancy. The quality of evidence ranged from high to very low. Diet Unknown benefit or harm: there was unknown benefit or harm of dietary advice versus standard care, on the risk of GDM: risk ratio (RR) 0.60, 95% CI 0.35 to 1.04; 5 trials; 1279 women; very low-quality evidence. There was unknown benefit or harm of a low glycaemic index diet versus a moderate-high glycaemic index diet on the risk of GDM: RR 0.91, 95% CI 0.63 to 1.31; 4 trials; 912 women; low-quality evidence. Exercise Unknown benefit or harm: there was unknown benefit or harm for exercise interventions versus standard antenatal care on the risk of GDM: RR 1.10, 95% CI 0.66 to 1.84; 3 trials; 826 women; low-quality evidence. Diet and exercise combined Possible benefit: combined diet and exercise interventions during pregnancy versus standard care possibly reduced the risk of GDM: RR 0.85, 95% CI 0.71 to 1.01; 19 trials; 6633 women; moderate-quality evidence. Dietary supplements Clear evidence of no effect: omega-3 fatty acid supplementation versus none in pregnancy had no effect on the risk of GDM: RR 1.02, 95% CI 0.83 to 1.26; 12 trials; 5235 women; high-quality evidence. Possible benefit: myo-inositol supplementation during pregnancy versus control possibly reduced the risk of GDM: RR 0.43, 95% CI 0.29 to 0.64; 3 trials; 502 women; low-quality evidence. Possible benefit: vitamin D supplementation versus placebo or control in pregnancy possibly reduced the risk of GDM: RR 0.51, 95% CI 0.27 to 0.97; 4 trials; 446 women; low-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of probiotic with dietary intervention versus placebo with dietary intervention (RR 0.37, 95% CI 0.15 to 0.89; 1 trial; 114 women; very low-quality evidence), or probiotic with dietary intervention versus control (RR 0.38, 95% CI 0.16 to 0.92; 1 trial; 111 women; very low-quality evidence) on the risk of GDM. There was unknown benefit or harm of vitamin D + calcium supplementation versus placebo (RR 0.33, 95% CI 0.01 to 7.84; 1 trial; 54 women; very low-quality evidence) or vitamin D + calcium + other minerals versus calcium + other minerals (RR 0.42, 95% CI 0.10 to 1.73; 1 trial; 1298 women; very low-quality evidence) on the risk of GDM. Pharmaceutical Possible benefit: metformin versus placebo given to obese pregnant women possibly reduced the risk of GDM: RR 0.85, 95% CI 0.61 to 1.19; 3 trials; 892 women; moderate-quality evidence. Unknown benefit or harm:eight small trials with low- to very low-quality evidence showed unknown benefit or harm for heparin, aspirin, leukocyte immunisation or IgG given to women with a previous stillbirth on the risk of GDM. Management of other health issues Clear evidence of no effect: universal versus risk based screening of pregnant women for thyroid dysfunction had no effect on the risk of GDM: RR 0.93, 95% CI 0.70 to 1.25; 1 trial; 4516 women; moderate-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of using fractional exhaled nitrogen oxide versus a clinical algorithm to adjust asthma therapy on the risk of GDM: RR 0.74, 95% CI 0.31 to 1.77; 1 trial; 210 women; low-quality evidence. There was unknown benefit or harm of pharmacist led multidisciplinary approach to management of maternal asthma versus standard care on the risk of GDM: RR 5.00, 95% CI 0.25 to 99.82; 1 trial; 58 women; low-quality evidence.

AUTHORS' CONCLUSIONS

No interventions to prevent GDM in 11 systematic reviews were of clear benefit or harm. A combination of exercise and diet, supplementation with myo-inositol, supplementation with vitamin D and metformin were of possible benefit in reducing the risk of GDM, but further high-quality evidence is needed. Omega-3-fatty acid supplementation and universal screening for thyroid dysfunction did not alter the risk of GDM. There was insufficient high-quality evidence to establish the effect on the risk of GDM of diet or exercise alone, probiotics, vitamin D with calcium or other vitamins and minerals, interventions in pregnancy after a previous stillbirth, and different asthma management strategies in pregnancy. There is a lack of trials investigating the effect of interventions prior to or between pregnancies on risk of GDM.

Low-Carbohydrate Diets for Gestational Diabetes

Nutrition therapy provides the foundation for treatment of gestational diabetes (GDM), and has historically been based on restricting carbohydrate (CHO) intake. In this paper, randomized controlled trials (RCTs) are reviewed to assess the effects of both low- and higher CHO nutrition approaches in GDM. The prevailing pattern across the evidence underscores that although CHO restriction improves glycemia at least in the short-term, similar outcomes could be achievable using less restrictive approaches that may not exacerbate IR. The quality of existing studies is limited, in part due to dietary non-adherence and confounding effects of treatment with insulin or oral medication. Recent evidence suggests that modified nutritional manipulation in GDM from usual intake, including but not limited to CHO restriction, improves maternal glucose and lowers infant birthweight. This creates a platform for future studies to further clarify the impact of multiple nutritional patterns in GDM on both maternal and infant outcomes.

Assessment of the methodological quality of local clinical practice guidelines on the identification and management of gestational diabetes

OBJECTIVE

Gestational diabetes is the most common metabolic disorder of pregnancy, and it is important that well-written clinical practice guidelines (CPGs) are used to optimise healthcare delivery and improve patient outcomes. The aim of the study was to assess the methodological quality of hospital-based CPGs on the identification and management of gestational diabetes.

DESIGN

We conducted an assessment of local clinical guidelines in English for gestational diabetes using the Appraisal of Guidelines for Research and Evaluation (AGREE II) to assess and validate methodological quality.

DATA SOURCES AND ELIGIBILITY CRITERIA

We sought a representative selection of local CPGs accessible by the internet. Criteria for inclusion were (1) identified as a guideline, (2) written in English, (3) produced by or for the hospital in a Western country, (4) included diagnostic criteria and recommendations concerning gestational diabetes, (5) grounded on evidence-based medicine and (6) accessible over the internet. No more than two CPGs were selected from any single country.

RESULTS

Of the 56 CPGs identified, 7 were evaluated in detail by five reviewers using the standard AGREE II instrument. Interrater variance was calculated, with strong agreement observed for those protocols considered by reviewers as the highest and lowest scoring based on the instrument. CPG results for each of the six AGREE II domains are presented categorically using a 5-point Likert scale. Only one CPG scored above average in five or more of the domains. Overall scores ranged from 91.6 (the strongest) to 50 (the weakest). Significant variation existed in the methodological quality of CPGs, even though they followed the guideline of an advising body. Specifically, appropriate identification of the evidence relied on to inform clinical decision making in CPGs was poor, as was evidence of user involvement in the development of the guideline, resource implications, documentation of competing interests of the guideline development group and evidence of external review.

CONCLUSIONS

The limitations described are important considerations for updating current and new CPGs.

Interventions to prevent women developing gestational diabetes mellitus: an overview of Cochrane Reviews

This is a protocol for a Cochrane Review (Overview). The objectives are as follows:

To summarise the evidence from Cochrane systematic reviews regarding the effects of interventions to prevent women developing gestational diabetes mellitus (GDM).

Effects of Bariatric Surgery on Maternal and Infant Outcomes of Pregnancy-An Evidence Analysis Center Systematic Review

BACKGROUND

While obesity presents specific acute and long-term risks to the pregnant woman and her offspring, the effects of bariatric surgery on pregnancy outcomes are undetermined.

OBJECTIVE

A systematic review was performed according to the Academy of Nutrition and Dietetics Evidence Analysis Library process to determine the effects of bariatric surgery on both maternal and infant health outcomes of pregnancy.

DESIGN

A comprehensive literature search of PubMed was conducted to identify studies published from years 2000 to 2015 that examined the health effects of pregnancy after bariatric surgery. Experimental studies and observational studies with a control group were included.

MAIN OUTCOME MEASURES

Outcomes of interest were gestational weight gain, maternal complications (ie, gestational diabetes, pre-eclampsia, eclampsia, hypertension, and postpartum hemorrhage), miscarriage and/or stillbirth, cesarean section, birth weight in grams, birth weight in categories (ie, macrosomia, low birth weight, small for gestational age, and large for gestational age), gestational age and preterm birth, infant illness and complications (ie, perinatal death, admission to neonatal intensive care unit, neonatal illness, and congenital malformation rates), and Apgar scores.

RESULTS

Thirteen of 246 studies were included. Compared to body mass index-matched controls without surgery, bariatric surgery before pregnancy reduced infant birth weight in grams, with no effect on total maternal gestational weight gain or Apgar scores. Surgery did not increase risk of adverse outcomes, such as miscarriage and/or stillbirth, preterm birth, or infant complications. Effects of surgery on maternal complications, infant birth weight categories, and surgical delivery rates were inconsistent.

CONCLUSIONS

Bariatric surgery is a successful treatment of maternal obesity, but certain surgery-specific risks may exist. More data are needed to determine clinical guidelines. The long-term effects of surgery on pregnancy outcomes are unknown.

The impact of diagnostic criteria for gestational diabetes on its prevalence: a systematic review and meta-analysis

BACKGROUND

The absence of universal gold standards for screening of gestational diabetes (GDM) has led to heterogeneity in the identification of GDM, thereby impacting the accurate estimation of the prevalence of GDM. We aimed to evaluate the effect of different diagnostic criteria for GDM on its prevalence among general populations of pregnant women worldwide, and also to investigate the prevalence of GDM based on various geographic regions.

METHODS

A comprehensive literature search was performed in PubMed, Scopus and Google-scholar databases for retrieving articles in English investigating the prevalence of GDM. All populations were classified to seven groups based-on their diagnostic criteria for GDM. Heterogeneous and non-heterogeneous results were analyzed using the fixed effect and random-effects inverse variance model for calculating the pooled effect. Publication bias was assessed by Begg's test. The Meta-prop method was used for the pooled estimation of the prevalence of GDM. Meta-regression was conducted to explore the association between prevalence of GDM and its diagnostic criteria. Modified Newcastle-Ottawa Quality Assessment Scale for nonrandomized studies was used for quality assessment of the studies included; the ROBINS and the Cochrane Collaboration's risk of bias assessment tools were used to evaluate the risk of bias.

RESULTS

We used data from 51 population-based studies, i.e. a study population of 5,349,476 pregnant women. Worldwide, the pooled overall-prevalence of GDM, regardless of type of screening threshold categories was 4.4%, (95% CI 4.3-4.4%). The pooled overall prevalence of GDM in the diagnostic threshold used in IADPSG criteria was 10.6% (95% CI 10.5-10.6%), which was the highest pooled prevalence of GDM among studies included. Meta-regression showed that the prevalence of GDM among studies that used the IADPSG criteria was significantly higher (6-11 fold) than other subgroups. The highest and lowest prevalence of GDM, regardless of screening criteria were reported in East-Asia and Australia (Pooled-P = 11.4%, 95% CI 11.1-11.7%) and (Pooled-P = 3.6%, 95% CI 3.6-3.7%), respectively.

CONCLUSION

Over the past quarter century, the diagnosis of gestational diabetes has been changed several times; along with worldwide increasing trend of obesity and diabetes, reducing the threshold of GDM is associated with a significant increase in the incidence of GDM. The harm and benefit of reducing the threshold of diagnostic criteria on pregnancy outcomes, women's psychological aspects, and health costs should be evaluated precisely.