The first International Association of Diabetes and Pregnancy Study Groups summit on the diagnosis of gestational diabetes in early pregnancy: TOBOGM Summit Report

Abstract

The first International Association of Diabetes and Pregnancy Study Groups Summit on the diagnosis of gestational diabetes in early pregnancy (Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) Summit) was held on the 17 November 2022 in Sydney, Australia. It sought to use the TOBOGM trial findings to scope the issues involved with early screening, to inform future discussions over possible approaches for diagnosing gestational diabetes mellitus (GDM) in early pregnancy. Most delegates supported testing for early GDM using a one‐step 75 g oral glucose tolerance test approach with Canadian Diabetes Association criteria preferred, but highlighted the importance of considering resources, cost, consumer perspectives and equity in translating TOBOGM results into a clinical approach to screening for, and diagnosing, early GDM.

INTRODUCTION

While approaches may differ, there is global agreement that screening for gestational diabetes mellitus (GDM: hyperglycaemia first detected in pregnancy and below diabetes in pregnancy (DIP: likely undiagnosed type 2 diabetes), should occur routinely at 24–28 weeks gestation. ¹ , ² International guidelines now also generally recommend early testing for women at high risk of DIP. ³ While glycaemic thresholds identifying DIP in early pregnancy are well established, ¹ , ² whether and how to define maternal hyperglycaemia below this threshold (early GDM diagnosed prior to 20–24 weeks gestation) is unclear. Until recently, high‐quality evidence for diagnosing and treating early GDM had been lacking.

A meta‐analysis of 13 cohort studies in women with early GDM demonstrated greater perinatal mortality (relative risk (RR) 3.58; 95% confidence interval (CI), 1.91–6.71) compared to women diagnosed with GDM in later pregnancy. ⁴ In the US EGGO randomised controlled trial (RCT), ⁵ early screening for GDM among 922 women with obesity using the Carpenter and Coustan two‐step, 100 g oral glucose tolerance test (OGTT) approach showed no difference in overall risk of perinatal complications. However, the trial included only a small number of women diagnosed and treated for GDM (69 (15.0%) in the early screening group vs 56 (12.1%) in the routine screening group, with the average gestational age at diagnosis 24.3 ± 5.2 weeks vs 27.1 ± 1.7 weeks, respectively). Its design did not allow a comparison of pregnancy outcomes between women with treated and untreated early GDM.

The recent Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) trial ⁶ was the first large multicentre international RCT to test diagnostic criteria and treatment for early GDM in women with risk factors for hyperglycaemia in pregnancy. TOBOGM showed that immediate treatment of GDM (two‐hour 75 g OGTT World Health Organisation (WHO) 2013 criteria) ² before 20 weeks gestation led to a reduction in the incidence of a composite of major adverse neonatal outcomes (odds ratio 0.82; 95% CI 0.68–0.98; number needed to treat (NNT) 18). Prespecified subgroup analyses suggested a greater effect from early intervention among women with (higher glycaemic band) Canadian Diabetes Association (CDA) diagnostic thresholds of fasting glucose (5.3–6.0 mmol/L, one‐hour glucose ≥10.6 mmol/L, and/or a two‐hour glucose level 9.0–11.0 mmol/L) versus the current (lower glycaemic band) WHO 2013 thresholds. No benefit and possible harm (increased incidence of small‐for‐gestational‐age babies) was seen with early treatment of women in the lower glycaemic band. At 24–28 weeks, in the deferred treatment group, GDM was diagnosed in 78.0% of women in the higher glycaemic band versus 51.4% in the lower band. Women who underwent OGTT prior to 14 weeks gestation had the greatest benefit in the composite of major adverse neonatal outcomes (odds ratio 0.75; 95% CI 0.57–0.98; NNT 12).

THE TOBOGM SUMMIT

The TOBOGM Summit emulated the International Association of Diabetes and Pregnancy Study Groups (IADPSG) process for gaining consensus over the 24–28 weeks gestation GDM diagnostic criteria following the publication of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) Study in 2008, ⁷ involving a series of workshops and setting up a writing group. ¹ A caveat to this process was that while these IADPSG criteria were adopted by the WHO and major international diabetes and obstetric organisations, ² , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² several national organisations either did not adopt the criteria, or proposed different criteria. ¹³ , ¹⁴ , ¹⁵ , ¹⁶ The rationale for not adopting the IADPSG/WHO criteria varied but largely came down to a predicted increase in workload with no RCT evidence of benefit. ¹⁴ , ¹⁷

The purpose of the first IADPSG Summit on the Diagnosis of Gestational Diabetes in early Pregnancy (TOBOGM Summit) was therefore to use the TOBOGM trial findings to scope the issues involved with early screening, to inform future discussions over possible approaches and criteria for diagnosing GDM in early pregnancy.

The Summit was hosted by the IADPSG on 17 November 2022, in Sydney, Australia. Over 170 delegates from 21 countries attended, representing a range of health professionals/clinicians, academics, policy makers and consumers with lived experience. Representatives from organisations with an interest in diabetes and pregnancy included the IADPSG, International Federation of Gynaecology and Obstetrics (FIGO), International Diabetes Federation (IDF), National Institutes of Health (NIH), and New South Wales Health. This short commentary summarises the TOBOGM Summit (available at: https://www.adips.org/asm.asp), representing the opinions of individual delegates of the Summit and does not necessarily reflect the position of the organisations they represent.

METHODOLOGY

Format and key questions at the summit

The Summit was divided into two parts ‐ presentations and workshops.

Presentations by leading international experts included a global overview on the prevalence, current screening practice and diagnostic criteria for GDM in early pregnancy, and issues relating to screening, diagnosis and treatment of hyperglycaemia in early pregnancy, different TOBOGM Study presentations including the results and consumer perspectives, followed by a panel discussion.

A series of workshops followed the presentations, where delegates discussed the following key questions.

1. Should we test for and treat GDM from early pregnancy?

2. What diagnostic criteria should we use for GDM in early pregnancy?

3. What are the issues over how we should screen for early GDM to decide who should have an OGTT?

4. What are the challenges in nomenclature/classification for GDM in early pregnancy?

5. What are the challenges and facilitators for translating findings from RCTs of when to test for and treat GDM from early pregnancy into practice?

The final workshop collated and presented the delegate discussions, provided international perspectives, and discussed future directions related to the Summit Report and roadmap to a framework for the diagnosis of GDM in early pregnancy.

Data collection and analysis

Feedback to the questions was collected through a pre‐ and post‐Summit survey, sent to all delegates. Issues were collated using an interactive graphic polling platform (SLIDO), audio recorded round‐table discussions and written comments, that explored perspectives on early GDM before and after presentation of the TOBOGM findings. No identifiable data were collected and delegates were aware that a summary of survey data and discussions would be disseminated via a Summit Report. Survey data were collated and descriptively analysed. Word clouds were downloaded from SLIDO. Audio recordings were manually transcribed. Transcripts and word cloud data were analysed using an inductive six‐step thematic analysis approach, ¹⁸ with the identified themes summarised.

FINDINGS

Most delegates prior to and following the Summit agreed that testing for early GDM should occur, that this should involve a one‐step 75 g OGTT, and that hyperglycaemia less than DIP early in pregnancy should be called ‘early GDM’ (Table 1). Following the TOBOGM presentation, there was a small increase in the proportion of delegates preferring early risk factor‐based screening to decide who should perform a subsequent early OGTT. The criteria preferred by most delegates for diagnosing early GDM shifted from the WHO (used as TOBOGM lower glycaemic band), to the CDA after the presentation.

Table 1.

Pre‐ and post‐Summit delegate survey data

Survey questions	Pre‐Summit (%)	Post‐Summit (%)
1. Should at least some women be tested and treated for GDM from early pregnancy?	Yes (95%) n = 133	Yes (93%) n = 119
2. What diagnostic criteria should be used for GDM in early pregnancy?	IADPSG (60%) Canadian (7.6%) Other (16.8%) n = 119	IADPSG (27%) Canadian (46%) Other (14%) n = 132
3. What test should be used?	75 g 2‐h OGTT (92%) n = 115	75 g 2‐h OGTT (99%) n = 97
4. How many blood test steps should there be?	One (89%) n = 113	One (95%) n = 108
5. How should we screen for early GDM to decide who should have an OGTT?	Those with DIP risk factors (69%) n = 126	Those with DIP risk factors (79%) n = 113
6. What should we call hyperglycaemia less than DIP?	Early GDM (76%) Other (15.8%) n = 127	Early GDM (77%) Other (11%) n = 117

n, number of delegate responses; GDM, gestational diabetes mellitus; IADPSG, International Association of the Diabetes and Pregnancy Study Groups diagnostic criteria for GDM (2‐h 75 g oral glucose tolerance test (OGTT): fasting glucose ≥5.1 mmol/L; and/or 1‐h glucose ≥10.0 mmol/L; and/or 2‐h glucose ≥8.5 mmol/L); Canadian Diabetes Association diagnostic criteria for GDM (2‐h 75 g OGTT: fasting glucose ≥5.3 mmol/L; and/or 1‐h glucose ≥10.6 mmol/L; and/or 2‐h glucose ≥9.0 mmol/L). DIP, diabetes in pregnancy.

Workshop discussion and SLIDO data showed broad support for testing and treating GDM in early pregnancy given the elevated risk shown with early hyperglycaemia. Overall, delegates felt there was insufficient evidence to currently define diagnostic criteria for GDM in early pregnancy. Several tests are currently used in clinical practice, including fasting glucose and HbA1c, especially in resource‐limited settings; however, the OGTT remains the only diagnostic test in early pregnancy evaluated in RCTs. Financial barriers, need for consensus and resources were the most frequent issues raised in relation to testing and treating GDM in early pregnancy, defining early GDM criteria, identifying who should undergo an early OGTT and translation into clinical care (Fig. 1). Other key issues were acceptability, the applicability of the TOBOGM findings in different populations/cohorts, which risk factors to select, equity (including access to an OGTT), the level of evidence required to revise diagnostic criteria for GDM, the need for re‐testing in later pregnancy, overdiagnosis and the potential risk of overtreatment. Participants also consistently expressed that for early testing to be effective there needs to be more education on accessing healthcare in the earlier stages of pregnancy. Major issues around nomenclature were stigma, confusion and consistency.

Figure 1.

Key issues relating to testing early in pregnancy for gestational diabetes mellitus identified via SLIDO word clouds at the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) Summit.

CONCLUSIONS AND FUTURE DIRECTIONS

Despite most delegates supporting testing for early GDM using a one‐step 75 g OGTT approach (CDA criteria preferred to IADPSG criteria), the TOBOGM Summit thematic analysis highlights the importance of considering resources, cost, consumer perspectives and equity in translating TOBOGM results into a clinical approach to early GDM. Health economic analyses may provide further clarity. Regarding future directions, there was broad consensus for the development of a writing group comprising relevant international stakeholders in DIP to define the approach and diagnostic criteria for early GDM addressing the issues raised. The impact on the diagnostic approach at 24–28 weeks gestation will also need to be considered. Additional RCTs are needed, including those in different populations. As such trials will take several years to fund, implement and report, consensus is needed on how and whether, in the interim, to progress from the TOBOGM findings to clinical service implementation.