Gestational diabetes

Gestational diabetes has long been a controversial topic.

Many women are told that they have gestational diabetes, but this term is not clearly defined. We do not have agreement on whether screening and treatment are beneficial, or on what screening and treatment should be offered.

This blog post shares some resources, especially from those who are questioning our current approach to gestational diabetes.

Information on Gestational Diabetes

There is plenty of information out there relating to the mainstream, medical approach to gestational diabetes. Resources include the NHS website, information from Diabetes UK, and the RCOG.

In the US, you might look at the CDC website, or the American Diabetes Association.

All of these resources are either government-led or not-for-profit, and freely available.

You will also find people offering to share information for a fee, but we have received a number of reports from people concerned about biased, non evidence-based information being shared in some forums on gestational diabetes, so please be careful. If a site, group, or person isn’t open to discussing all of the opinions or perspectives on a topic, or if they shut down people who share other perspectives, then you might want to consider steering clear of them. That attitude is a good indication of bias and closed mindedness. More on how to appraise information in What’s Right For Me?

Questioning the medical approach

There is a growing conversation which questions the mainstream, medical approach to gestational diabetes, so there is good reason to look at ALL of the perspectives in order to decide what’s right for you.

I became aware of the lack of evidence base for some of what is being told to women in this area when I wrote In Your Own Time and then Plus Size Pregnancy.

I discovered that there was a lack of evidence to support things that women were being told.

A good example here relates to induction and gestational diabetes, which I have written about separately.

Cochrane reviewers agree with my assessment that there is no evidence to show whether induction makes any difference to women with gestational diabetes and their babies.

So there is good reason to be open minded and to ask questions.

Why the discrepancy?

Some people have long been skeptical about how gestational diabetes is defined. One of the key issues here is with the definitions of gestational diabetes.

One example of how the cut-off points change happened in Australia, where, “…the change in glucose cut-offs in 2014 led to a significant increase in gestational diabetes diagnosis.” (Peters et al 2025).

And change isn’t necessarily for the better. Another recent study found that these new, tighter, cut-off points, “…were not associated with improved perinatal outcomes but were associated with an increase in pharmacotherapy [prescribing drugs to pregnant women].“ (Montalto et al 2025.)

If you are told you have gestational diabetes, what you are offered – and also what you are told you now may not do – also differs by area.

It’s confusing, contradictory, and absolutely not what you want to be dealing with in pregnancy.

More on the controversy

This is supported by other evidence. One of the Cochrane reviews on this topic also shows that there is “insufficient evidence to suggest which strategy is best for diagnosing GDM” (Farrar et al 2017).

Other Cochrane reviews, including that by Tieu et al (2017) agree. “There is not enough evidence to guide us on effects of screening for GDM based on different risk profiles or settings on outcomes for women and their babies.”

There are some short-term benefits to women with gestational diabetes who receive lifestyle interventions compared to women with gestational diabetes who didn’t (Brown et al 2017).

But it might be that these are beneficial to all pregnant women, not just those with gestational diabetes.

The overdiagnosis problem

An even more recent paper has further illuminated the problem of overdiagnosis.

Karentius et al (2025) set out to look at this problem, explaining that, “Overdiagnosis is an increasing issue in modern medicine and poses harm to the public while putting pressure on healthcare resources.”

These researchers pointed out that, “The incidence of gestational diabetes mellitus is increasing globally, reflecting intensified screening efforts alongside substantial international differences in how, when, and by which criteria screening is conducted, and diagnoses are determined.” (Karentius et al 2025).

This research team carried out a systematic synthesis of evidence from randomised controlled trials, and, “…highlights overdiagnosis as a likely consequence of universal screening for gestational diabetes mellitus.” (Karentius et al 2025)

“Our analysis of RCT data demonstrates that intensifying screening led to increased incidence without corresponding beneficial effects, indicating overdiagnosis. Few studies have assessed overdiagnosis empirically, and no established framework currently guides the definition or operationalisation of overdiagnosis in GDM screening research.” (Karentius et al 2025)

The bigger picture

This is vital evidence, but there is also, as Hegarty (2020) discusses, a far bigger picture to consider.

He points out that:

• “Evidence‐based benefits from treatment are much less than is generally believed
• While few babies can benefit, all babies treated, particularly pharmacologically, are exposed to potential harm
• All treated babies have their growth and lean mass reduced, which may be detrimental, particularly as the majority are already of normal or small size
• The pharmacological intensification of treatment is not based on sound evidence, is probably unnecessary, potentially harmful, and should be ceased until there is better evidence for benefit and safety, and
• If parents are not correctly informed about these matters they cannot properly consent to GDM‐related interventions in their otherwise normal pregnancies, and this becomes important if interventions lead to problems.” (Hegarty 2020).

Another excellent resource on this topic is Rachel Reed’s Gestational Diabetes: beyond the label, in which she offers loads more information, and two podcast episodes (scroll to the bottom of the post) in which she shares her knowledge on this topic.

The 2020 Cochrane summary

Similar issues are reflected in a summary of the evidence which has been analysed by the Cochrane Collaboration. This shows how very little evidence there is for the screening and treatment that women are offered.

“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.” (Griffith et al 2020).

Again, many women are also offered induction for gestational diabetes, although there is no evidence that this is beneficial – see this blog post for more information on that.

Induction for gestational diabetes: what’s the evidence?

The short term problem

Some people will rightly point out that we shouldn’t only be looking at short-term outcomes, reminding us that there is some evidence that gestational diabetes is a marker of increased risk for cardiovascular and metabolic diseases among women in later life (e.g. Lane‐Cordova et al 2019).

There are also concerns about the longer-term outcomes of babies with macrosomia.

But, again, there are no direct correlations here. Markers are complex things, and intervention doesn’t necessarily reduce risk. But it can cause knock-on problems.

As in so many areas of maternity care, the diagnosis, labelling (which can lead to a restriction of options due to perceived risk status), and treatment of gestational diabetes has affected the experiences of hundreds of thousands of women.

Around the world, there are considerable discrepancies in the assessment, diagnosis, care and treatment offered to women in this area.

How can all of this be justified without there being good and clear evidence of benefit?

A definition problem

This area was also highlighted some years ago by Michel Odent, who describes gestational diabetes as “a diagnosis looking for a disease”:

“Gestational diabetes is a typical example of a term with a strong nocebo effect.  It has the power to transform a happy pregnant woman into an anxious or depressed one … One of the side effects of the term ‘gestational diabetes’ is to transform the interpretation of the results of a test into a disease. The status of disease implies that complications have been identified.  It is commonplace to claim that macrosomia (a big baby) is the main complication. This should be considered an association. It is obvious that the energy requirements of a big baby are not the same as the requirements of a small one: the mother, who must make a bigger effort than others, is labelled as having ‘gestational diabetes’ … The nocebo effect of the term ‘gestational diabetes’ is becoming a serious issue. The use of enlarged criteria to interpret the tests is one of the reasons why the number of women diagnosed with gestational diabetes is increasing” (Odent 2013: 100-02).

Everyone should get good advice

I’m not suggesting for a moment that health care professionals shouldn’t be offering good nutritional advice. Or be concerned about optimising the health of individual women. These have long been good cornerstones of good midwifery care.

But midwives and doctors should be offering good nutritional advice, and advice on movement, to all women who want it, not just those who get a particular test result on a certain day. (And not to those who don’t, because we need to move away from an approach rooted in weight bias.)

I believe that health care professionals should take a wide and ideally holistic perspective which is actually evidence-based, rather than being rooted in older theories and disproven ideas about body weight and size.

But this isn’t happening.

Women and families need to know that we don’t have good answers, a sound, deep understanding of gestational diabetes, and good evidence of benefit of the interventions that are being offered.

And that systems of health care are imposing diagnoses, labelling, and interventions which may not always be of benefit, and which may cause harm.

That way, everyone can weigh up the pros and cons of what they’re being offered, look at ALL of the available information and evidence, and then make the decisions that are right for them.

Some of my books look in more depth at this and related areas.

More resources

Plus Size Pregnancy

In Your Own Time

What’s Right For Me?

References

Please also see the links in this blog post.

Brown J, Ceysens G, Boulvain M. Exercise for pregnant women with gestational diabetes for improving maternal and fetal outcomes. Cochrane Database of Systematic Reviews 2017, Issue 6. Art. No.: CD012202. DOI: 10.1002/14651858.CD012202.pub2

Farrar D, Duley L, Dowswell T et al (2017). Different strategies for diagnosing gestational diabetes to improve maternal and infant health. Cochrane Database of Systematic Reviews 2017, Issue 8. Art. No.: CD007122. DOI: 10.1002/14651858.CD007122.pub4

Griffith RJ, Alsweiler J, Moore AE et al (2020). Interventions to prevent women from developing gestational diabetes mellitus: an overview of Cochrane Reviews. Cochrane Database of Systematic Reviews 2020, Issue 6. Art. No.: CD012394. DOI: 10.1002/14651858.CD012394.pub3.

Hegarty CK (2020). The new gestational diabetes: Treatment, evidence and consent. ANZJOG 60: 482-485.  DOI: 10.1111/ajo.1311

Lane‐Cordova AD et al (2019). Long-term cardiovascular risks associated with adverse pregnancy outcomes. J Am Coll Cardiol , 2019, 73:2106‐2116.

Odent M (2013).  Childbirth and the future of homo sapiens.  Pinter and Martin, London.

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