Lower GDM diagnostic thresholds doubled diagnoses without better short-term outcomes

The study

This is a systematic review and meta-analysis published in The Journal of Clinical Endocrinology and Metabolism (Liu Q, Mayer DFR, Harding JE et al.). It asked how outcomes differ when gestational diabetes (GDM) is diagnosed on an oral glucose tolerance test using lower versus higher diagnostic criteria or thresholds.

The authors searched four databases and four trial registries up to 27th July 2026. They looked for randomised controlled trials (RCTs) and prospective cohort studies. These had to compare outcomes after assessment for GDM, with treatment if indicated, under lower or higher criteria. The review is registered in PROSPERO (CRD420251183179). Two reviewers independently assessed risk of bias, ran random-effects meta-analyses and evaluated GRADE certainty.

Seventeen studies were included. Nine RCTs and one cohort study contributed to the meta-analysis, covering 81,528 women.

What they found

Compared with higher criteria or thresholds, lower criteria or thresholds:

• doubled the diagnosis of GDM
• doubled the use of pharmacotherapy
• increased neonatal hypoglycaemia. In the RCTs this was 18 more per 1,000 (95% CI 11 to 25 more).
• increased maternal-neonatal separation. In the RCTs this was 6 more per 1,000 (95% CI 1 to 12 more).

The authors found little to no effect on other short-term outcomes.

Longer-term evidence was limited to follow-up of one RCT. At five years, lower criteria or thresholds were linked to reduced maternal hypertension and reduced child neurodevelopmental impairment. They were also linked to increased subsequent GDM. The abstract does not report effect sizes for these long-term findings.

Findings on GDM-related healthcare costs were inconsistent. There were no long-term economic data.

How much weight to give it

The authors concluded that lower criteria increased GDM diagnosis and some aspects of healthcare use without improving short-term outcomes. They described the longer-term evidence as limited, suggesting possible benefits.

Nine RCTs and one cohort study (81,528 women) contributed to the meta-analysis. The neonatal figures quoted above come from the RCTs. The abstract does not report the GRADE certainty of these findings, so their strength cannot be judged from the abstract alone.

The long-term findings are more limited still. They come from a single RCT, and the authors called for further long-term follow-up from high-quality RCTs. The reported benefit for hypertension and neurodevelopment sits beside a higher rate of later GDM.

The abstract also does not report the specific thresholds compared, heterogeneity between studies, how neonatal hypoglycaemia was defined, or funding. Read the full paper for these details.

For your clinic

These results suggest that lowering diagnostic thresholds has costs that are easy to see in the short term. More women receive a diagnosis and more receive drug treatment. More babies have hypoglycaemia and more mothers and babies are separated. The abstract shows no clear short-term gain to offset this.

For services that use or are considering lower criteria, this is a reason to look at the workload, neonatal monitoring and the effect on mothers. It is not a reason to change local practice alone. The possible longer-term benefits rest on one trial and are still uncertain. Check the full paper and current national or professional guidelines before any change in diagnostic criteria. Individual decisions about testing and treatment should stay with the treating team.