Study reveals more than half of gestational diabetes cases in the UK go undiagnosed

A groundbreaking study has revealed that more than half of pregnant individuals with gestational diabetes in the UK are not being diagnosed under the current NHS blood testing procedures. This diagnostic gap could result in avoidable complications affecting both the parent and the baby.

The research, led by Professor Claire Meek of the University of Leicester in collaboration with colleagues from the University of Cambridge, highlights the need for faster processing of blood samples during the oral glucose tolerance test (OGTT). The study indicates that speeding up this process could significantly improve the accuracy of gestational diabetes diagnoses.

The findings, published in the journal Diabetic Medicine on 17 December, shed light on the shortcomings of existing testing protocols and propose a simple, yet transformative solution.

Professor Claire Meek, Professor of Chemical Pathology and Diabetes in Pregnancy, explained the critical impact of this condition, “Gestational diabetes, which affects women in pregnancy, is very common in the UK and causes complications at the time of birth, affecting both mother and child. Fortunately, most complications can be prevented by accurate diagnosis and access to treatment. However, if the diagnosis is not accurate, then affected mothers cannot access the treatment they need.”

Gestational diabetes is typically diagnosed between 24 and 28 weeks of pregnancy using the OGTT. This process involves taking an initial blood sample before the individual consumes a sugary drink, followed by a second sample two hours later. However, red blood cells continue to metabolise glucose after the sample is taken, leading to a reduction in glucose concentration over time and potentially skewing results.

Processing the blood more quickly ensures the glucose levels in the sample reflect those in the individual’s bloodstream more accurately.

Professor Meek further elaborated, “We wanted to assess if processing the samples more quickly improved the accuracy of the OGTT test. We compared standard NHS sample processing procedures to an enhanced processing plan, where the blood was processed more quickly.”

The study found stark differences in the outcomes between the two methods. Using standard NHS processing, 9% of participants were diagnosed with gestational diabetes. However, when blood samples were processed more promptly, this figure rose to 22%, indicating that 13% of individuals were missed using the current procedures.

This oversight could have significant implications at scale, potentially leaving 28,000–30,000 pregnant individuals undiagnosed each year in the UK.

Danielle Jones, the PhD student who coordinated the research, highlighted the downstream impact of these missed diagnoses, “Faster blood processing identified additional women with raised blood sugar levels that were missed by the standard test. Thirty-seven percent of these women went on to have large babies—a complication which could have been prevented if undiagnosed women had access to treatment.”

Large babies, or macrosomia, are associated with a range of complications during delivery and beyond, but timely treatment can mitigate these risks.

The study underscores the need for NHS settings to adopt improved sample processing procedures. Processing blood within two to four hours is deemed achievable and could lead to dramatic improvements in the health outcomes of both parents and their babies.

These findings pave the way for an urgently needed update to current NHS protocols, ensuring accurate diagnoses and better access to treatments for those affected by gestational diabetes. This change could transform outcomes for tens of thousands of families each year.