Gestational diabetes

Gestational diabetes has long been a controversial topic. The controversy is well summarised by an opinion paper published in the Australian and New Zealand Journal of Obstetrics and Gynaecology. This paper echoes the concerns of many midwives, obstetricians and others about the diagnosis and treatment of gestational diabetes. The author points out that, “Despite the increasing numbers of women diagnosed, there is little to suggest outcomes are improved.” (Hegarty 2020).

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). While there are some short-term benefits to women with GD who receive lifestyle interventions compared to women with GD who didn’t (Brown et al 2017), it might be that these are beneficial to everyone. There is also, as Hegarty (2020) discusses, a far bigger picture to consider.


The key issues

Dr Christopher K. Hegarty, the author of the article under discussion, 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).


The 2020 Cochrane summary

Similar issues are reflected in a summary of the evidence which has been analysed by the Cochrane Collaboration:

“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).

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. The problem here is that 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: 100-102).


Everyone should get good advice

If you’re a midwife or birth worker who can see the problems that we’re facing and you want to discuss evidence from a woman-centred perspective, our online courses are a safe space in which to do that.

I’m not suggesting for a moment that we 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 we should be offering good nutritional advice, and advice on movement, to all women, not just those who get a particular test result on a certain day. And we should absolutely be investigating these concerns.

We 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, fatness and the like. We should research all angles of this topic. But shouldn’t we wait for answers, a deeper understanding and good evidence of benefit before imposing new diagnoses, labelling and interventions which may not be of benefit and which may cause harm?


I’d like to thank Dr Kirsten Small for reading a draft of this article.


This was a ‘study of the month’ in my Birth Information Update, a monthly newsletter in which I share up-to-date birth-related research and thinking. If you’d like to hear about new research, make sure you’re subscribed to our free newsletter list, which means you’ll get Sara’s monthly Birth Information Update and details of our current projects.
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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, Lawlor DA. 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, Brown S, Middleton P, Shepherd E, Crowther CA. 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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