First trimester fasting glucose and glycated haemoglobin cut-offs associated with abnormal glucose homeostasis in the post-partum reclassification in women with hyperglycaemia in pregnancy

Challenging the American College of Obstetricians and Gynecologists' Clinical Practice Update on Screening for Pre-existing Diabetes and Early Gestational Diabetes

A recent American College of Obstetricians and Gynecologists Clinical Practice Update continues to recommend targeted (as opposed to universal) screening for pregestational diabetes, no longer recommends screening for early gestational diabetes mellitus (GDM), and provides updated guidelines for immediate postpartum testing for diabetes in patients with GDM. Here, we present data that the targeted screening paradigm, which has repeatedly been shown to fail in practice because of its complexity, no longer makes sense in the context of the high and rising prevalence of diabetes and diabetic risk factors, and we argue that the time has come for universal early pregnancy screening for pregestational diabetes. Furthermore, the recommendation against early screening for GDM is based on 2021 U.S. Preventive Services Task Force guidance, which in turn is based almost entirely on a single underpowered study that excluded individuals at highest risk and does not account for more recent research showing benefits of early diagnosis and treatment. Universal early pregnancy screening for pregestational diabetes may also help to identify patients at risk who will benefit from early GDM diagnosis and treatment and may provide rationale for prioritizing postpartum diabetes testing.

First-trimester fasting plasma glucose levels and progression to type 2 diabetes: A 5-year cohort study

OBJECTIVE

Impaired fasting glucose is a prediabetic condition defined as glucose levels of 100-125 mg/dL and is considered a risk factor for type 2 diabetes. However, this definition does not confer to pregnancy. The significance of first-trimester fasting glucose and future progression to diabetes is not well defined. Therefore, we aimed to evaluate the progression to type 2 diabetes according to first- trimester fasting plasma glucose levels, as compared with gestational diabetes, a well-established risk factor for diabetes, in up to 5-year follow-up postpartum.

METHODS

A retrospective analysis of 69 001 parturients, evaluating fasting plasma glucose levels measured during the first trimester. The primary outcome was the incidence of type 2 diabetes within 5 years post-delivery. Fasting plasma glucose levels were categorized in 10 mg/dL increments. Receiver operating characteristic-area under the curve (ROC-AUC) statistics and the Youden index were employed to identify the optimal fasting plasma glucose cutoff for progression to type 2 diabetes. Survival analysis was applied to calculate the adjusted hazard ratios (aHRs) for type 2 diabetes progression with further stratification to maternal obesity status.

RESULTS

The identified fasting plasma glucose cutoff for progression to type 2 diabetes was 86.5 mg/dL. This cut-off demonstrated superior performance compared with gestational diabetes diagnosis. Stratification by maternal obesity revealed enhanced predictive capabilities for type 2 diabetes, particularly among patients without obesity.

CONCLUSIONS

Increased first-trimester fasting plasma glucose levels are associated with progression to type 2 diabetes, at least as gestational diabetes. For patients without obesity, first-trimester fasting plasma glucose has a more pronounced impact on progression to diabetes.

Is early pregnancy hemoglobin A1c useful to predict gestational diabetes mellitus diagnosed during mid pregnancy?

AIMS

To verify whether hemoglobin A1c (HbA1c) levels in early pregnancy can predict the diagnosis of gestational diabetes mellitus (GDM) in mid-pregnancy.

MATERIALS AND METHODS

This was a retrospective cohort study of 2008 pregnant women who delivered singletons at the Yokohama City university Medical Center. Concomitant or history of diabetes mellitus and overt diabetes in pregnancy were excluded. Pregnant women at high risk for GDM underwent a one-step 75-g oral glucose tolerance test (OGTT) during mid-pregnancy. For other pregnant women, GDM was diagnosed by a two-step 75-g oral glucose tolerance test (OGTT) when the 50-g glucose challenge test result in mid-pregnancy was ≥140 mg/dL. The thresholds for 75-g OGTT followed those of the International Association of Diabetes and Pregnancy Study Group (IADPSG) criteria (92-180-153 mg/dL). The relationship between HbA1c level measured at <20 weeks of gestation and GDM diagnosis at mid pregnancy was assessed using a receiver operating characteristic curve (ROC); area under the curve (AUC) and optimal cutoff value of HbA1c, predictive of GDM were calculated.

RESULTS

The median HbA1c level at <20 weeks of gestation was 5.3%, and 8.5% of women were diagnosed with GDM. In the ROC curve of the GDM diagnosis rate by HbA1c level, AUC was 0.706, and the optimal cutoff value was 5.4%, with a sensitivity of 0.6176, specificity of 0.6834, positive predictive value of 15.4%, and negative predictive value of 95.1%.

CONCLUSIONS

Although HbA1c at less than 20 weeks of gestation is acceptable discrimination as a diagnostic tool of GDM in mid-pregnancy, it is not clinically useful to predict GDM in mid-pregnancy.

Maternal modifiable factors and risk of congenital heart defects: systematic review and causality assessment

OBJECTIVE

Primary prevention strategies are critical to reduce the global burden of congenital heart defects (CHDs); this requires robust knowledge of causal agents. We aimed to review associations between CHDs and maternal advanced age, obesity, diabetes, hypertension, smoking and alcohol consumption and assess the causal nature of the associations.

DESIGN

Systematic review of reviews with application of a Bradford Hill criteria score-based causal assessment system.

DATA SOURCES

We searched PubMed, Embase and Episteminokos (January 1990-April 2023).

ELIGIBILITY CRITERIA

Systematic reviews of original epidemiological studies reporting association (relative risk) between one or more of the above maternal factors and CHDs overall (any type) in subsequent offspring.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers selected eligible reviews, assessed the risk of bias and assigned the strength of evidence for causality.

RESULTS

There was strong evidence of a causal relationship between CHDs and maternal obesity (prepregnancy and early pregnancy) and pre-existing diabetes (six of seven Bradford Hill criteria met). For pre-existing hypertension (strength and biological gradient not met), and advanced age (strength, consistency and biological gradient not met), causal evidence was moderate. Evidence for the causal contribution of gestational diabetes, gestational hypertension, smoking and alcohol consumption was weak (strength, consistency, temporality and biological gradient not met).

CONCLUSIONS

CHDs can be reduced with stronger action to reduce maternal obesity and pre-existing diabetes prevalence. Investigating environmental exposures that have received limited attention, such as air pollutants and chemical exposures, is important to further inform prevention.

Timing of gestational diabetes diagnosis and progression to type 2 Diabetes: A comparative analysis

AIM

To evaluate and compare the risk of progressing to type 2 diabetes (T2DM) based on the timing of gestational diabetes (GDM) diagnosis during pregnancy.

METHODS

Retrospective analysis of pregnant individuals with gestational diabetes and post-pregnancy follow up. Data sourced from Meuhedet HMO's computerized laboratory system, cross-tabulated with the Israeli National Diabetes Registry. The cohort was divided into normoglycemic, early GDM (diagnosed by fasting plasma glucose 92-125 mg/dL (5.1-6.9 mM) at < 15 weeks), 2nd trimester GDM (diagnosed at 24-28 weeks), and late GDM (diagnosed after 29 weeks). Statistics included univariate analysis followed by survival analysis. Risk was further analyzed for individuals by obesity status.

RESULTS

75,459 entered the analysis: 90 % normoglycemic, 7.9 % early GDM, 1.4 % 2nd trimester GDM, and 0.7 % late GDM. Median post-pregnancy follow-up time was 4.3 (IQR 3.3-5.1). 2nd trimester GDM showed the highest T2DM risk annually after pregnancy. Cox regression analysis, adjusted for confounders, revealed a significantly higher T2DM risk for 2nd-trimester GDM compared to early and late GDM. Late GDM did not confer additional significant T2DM risk. Stratification by obesity status highlighted that early GDM increased the risk of T2DM only in individuals without obesity.

CONCLUSIONS

GDM diagnosis timing significantly impacts T2DM risk. 2nd trimester GDM carries the highest T2DM risk.

Time to Move Beyond a Binary Criterion for Gestational Diabetes?

Over the years, several international guidelines have been developed by specialist organizations for the diagnosis of gestational diabetes mellitus (GDM). However, these guidelines vary and lack consensus on what level of glycemia defines GDM and worryingly, there is now evidence of over- or- under-diagnosis of women with GDM by current criteria. Towards this end, the National Priorities Research Program (NPRP) funded a program of research aimed at elucidating the problem with GDM diagnosis. It was determined, on completion of the project, that the solution required diagnosis of graded levels of dysglycemia in pregnancy and not just a diagnosis of presence or absence of GDM. A new diagnostic criterion (called the NPRP criterion) was created based on a single numerical summary of the three readings from the oral glucose tolerance test (GTT) that diagnosed women in pregnancy into four levels: normal, impaired, GDM and high risk GDM. This paper now examines existing GDM criteria vis-à-vis the NPRP criterion. It is noted that no significant change has happened over the years for existing criteria except for a gradual reduction in the threshold values of individual time-points or the number of time points, bringing us towards over-diagnosis of GDM in pregnancy. The new criterion unifies all readings from the GTT into one numerical value and, because it results in four levels of glycemia, represents a new way forwards for GDM diagnosis and can potentially reduce the rates of under diagnosis and over diagnosis of GDM.

Determination of the Contributing Factors and HbA1c Cutoff Leading to Glucose Tolerance Abnormalities Following Gestational Diabetes

The prevalence of gestational diabetes mellitus (GDM) has been steadily increasing over the past years. It is a major risk factor for glucose intolerance and type 2 DM (T2DM). The American Diabetes Association recommends that women whose pregnancy was complicated by GDM be screened for persistent glucose abnormalities at six to 12 weeks postpartum with either a fasting plasma glucose test alone or with a fasting 75-g, two-hour oral glucose tolerance test. This study aimed to identify the main predictive factors of glucose tolerance disorders in early postpartum women with a recent history of GDM. In this retrospective descriptive study, we identified 400 women who met the eligibility criteria for the study. The mean age was 34.54 ± 5.51 years. A total of 70% had a family history of DM, 16% had a personal history of GDM, and 23% had fetal macrosomia in previous pregnancies. The overall incidence of postpartum carbohydrate tolerance disorders was 36.4%, including 12% prediabetes and 24.4% DM. The prevalence of prediabetes and T2DM after delivery was higher with older maternal age, multigravidity, a higher BMI, a history of GDM, and fetal macrosomia in previous pregnancies. Furthermore, the persistence of this impaired glucose tolerance in postpartum was associated with a higher term of diagnosis, a higher glycated hemoglobin (HbA1c) percentage (the discriminant cutoff value with the best sensitivity/specificity ratio was 5.25%), the use of insulin therapy, cesarean section delivery, and fetal macrosomia. After adjusting for confounders, only prior GDM, a higher HbA1c level, macrosomia, and gestational term were found to significantly affect postpartum glucose tolerance. Although postpartum screening for T2DM is recommended for all women with GDM, a significant number of patients fail it. A better knowledge of predictive factors for this outcome is therefore needed for a more effective and targeted medical intervention.

Use of oral glucose tolerance testing and HbA1c at 6-14 gestational weeks to predict gestational diabetes mellitus in high-risk women

PURPOSE

To study the prediction of gestational diabetes mellitus (GDM) in high-risk pregnant women by testing fasting blood glucose, 1-h(1hPG) and 2-h plasma glucose (2hPG) after an oral glucose tolerance test, and glycated hemoglobin (HbA1c) in early pregnancy (6-14 weeks).

METHODS

We recruited 1311 pregnant women at high risk for diabetes from the Obstetrics Clinic of Daxing District People's Hospital between June 2017 and December 2019. The tests performed during the first trimester included fasting blood glucose (FPG), HbA1c, and 75-g oral glucose tolerance test (OGTT) with 1hPG and 2hPG. Seventy-three pregnant women diagnosed with pregestational diabetes mellitus (PGDM) early in pregnancy and 36 who were missed in the second trimester were excluded. A total of 1202 women were followed up until 24-28 weeks for GDM. The receiver operating characteristic (ROC) and area under the ROC curve (AUC) were calculated to determine the predictive values of FPG, 1hPG, 2hPG, and HbA1c for GDM in early pregnancy in high-risk pregnant women.

RESULTS

The AUC for 1hPG for the prediction of GDM in high-risk pregnant women was greater than those for FPG, 2hPG, and HbA1c. All differences were significant. The AUCs for the predictive values of FPG, 1hPG, 2hPG, and HbA1c in high-risk pregnant women were 0.63, 0.76, 0.71, and 0.67, respectively. The prevalence of PGDM among pregnant women at high risk of diabetes was 5.6%.

CONCLUSION

First-trimester levels of FPG, 1hPG, 2hPG, and HbA1c in high-risk women are significant predictors of GDM, with 1hPG having the most significant predictive value.

Early Gestational Diabetes Mellitus: Diagnostic Strategies and Clinical Implications

Preexisting diabetes mellitus (DM) should be ruled out early in pregnancy in those at risk. During screening, a significant proportion of women do not reach the threshold for overt DM but fulfill the criteria used for diagnosing conventional gestational DM (cGDM). There is no consensus on the management of pregnancies with intermediate levels of hyperglycemia thus diagnosed. We have used the term early gestational DM (eGDM) for this condition and reviewed the currently available literature. Fasting plasma glucose (FPG), oral glucose tolerance test, and glycated hemoglobin (HbA1c) are the commonly employed screening tools in early pregnancy. Observational studies suggest that early pregnancy FPG and Hba1c correlate with the risk of cGDM and adverse perinatal outcomes. However, specific cut-offs, including those proposed by the International Association of the Diabetes and Pregnancy Study Group, do not reliably predict the development of cGDM. Emerging data, though indicate that FPG ≥ 92 mg/dL (5.1 mmol/L), even in the absence of cGDM, signals the risk for perinatal complication. Elevated HbA1c, especially a level ≥ 5.9%, also correlates with the risk of cGDM and worsened outcome. HbA1c as a diagnostic test is however besieged with the usual caveats that occur in pregnancy. The studies that explored the effects of intervention present conflicting results, including a possibility of fetal malnutrition and small-for-date baby in the early treatment group. Diagnostic thresholds and glycemic targets in eGDM may differ, and large multicenter randomized controlled trials are necessary to define the appropriate strategy.