Gestational Diabetes


Published: 31 May 2021

What is Gestational Diabetes?

Gestational diabetes mellitus (GDM) is a condition that affects about 16% of pregnant people in Australia (AIHW 2020).

By definition, GDM is any degree of glucose intolerance following the onset of pregnancy (VIC DoH 2018).

It is usually detected between weeks 24 and 28 of pregnancy and disappears once the baby has been born (Healthdirect 2019).

GDM can be dangerous for both mother and baby if not managed appropriately (NHS 2019).

Risk Factors for Gestational Diabetes

  • Maternal age of over 40
  • Previous hyperglycaemia or gestational diabetes
  • Family history of type 2 diabetes or a first-degree relative with previous GDM
  • Pre-pregnancy BMI of over 30
  • Being of a certain ethnic background (including Aboriginal or Torres Strait Islander, African, Melanesian, Polynesian, South Asian, Chinese, Southeast Asian, Middle Eastern, Hispanic and South American)
  • Polycystic ovarian syndrome
  • Previous large baby weighing 4.5kg or more
  • Taking antipsychotic or steroid medicines.

(The Women’s 2020; Diabetes Australia n.d.)

Symptoms of Gestational Diabetes

gestational diabetes symptoms thirst

In most cases, there are no obvious symptoms. However, some people may experience:

  • Increased thirst
  • Excessive urination
  • Fatigue
  • Thrush infection.

(Better Health Channel 2019)

What Causes Gestational Diabetes?

GDM occurs when there are such high levels of glucose in the blood that the body cannot produce enough insulin to absorb it all (Better Health Channel 2019).

This is caused by the placental hormones produced during pregnancy, which make it difficult for the body to use insulin efficiently (a process known as insulin resistance) (Better Health Channel 2019).

As pregnancy places a high demand on the body, some people aren’t able to produce enough insulin to overcome this resistance. The result is that glucose may remain in the blood at higher levels than normal, leading to GDM (Better Health Channel 2019).

Whilst most people with gestational diabetes have normal pregnancies and healthy babies, the risk of certain complications is increased for both mother and baby (NHS 2019).

For example, the foetus may grow larger than normal, causing problems during delivery and increasing the chance of requiring a caesarean birth. The incidence of premature birth, neonatal jaundice or stillbirth may also be higher (NHS 2019).

Managing Obesity During Pregnancy

People can significantly reduce their risk of developing gestational diabetes by managing their weight, keeping active and eating a healthy diet (Better Health Channel 2019).

Wang et al. (2015) suggest that a higher body mass index (BMI) before or during the first trimester of pregnancy and excessive gestational weight gain (GWG) are early markers of gestational diabetes.

High BMI and excessive GWG also increase the likelihood that both the mother and baby will remain overweight for a decade or more after birth, leading to a continuing cycle of excessive GWG, obesity and GDM (Wang et al. 2015).

Kampmann et al. (2015) suggest the need to address an increase in obesity in people of childbearing age, as in recent years, there has been a sharp rise in the incidence of overweight and obese people and a consequent rise in complications during pregnancy and birth.

Not only does GDM put both mother and baby at risk of serious long-term consequences, but it also puts a significant additional strain on the healthcare system.

Gestational Diabetes and Warm Weather

gestational diabetes warm weather

Less well-known are the risks of developing GDM in warm weather.

Several researchers have noted that more cases occur in the summer months, suggesting that the condition may be seasonal, or that misdiagnosis could be more likely during warm months of the year (Ford 2018).

Vasileiou et al. (2017) also found that during the summer months, average non-fasting blood sugar values were higher compared to those in winter.

One reason for this may be an increase in blood flow in warm weather that diminishes sugar extraction from blood to tissue (Vasileiou et al., as cited in Ford 2018).

Similar studies exploring the link between warmer weather and GDM found that glucose levels tended to increase when it was hotter and that the summer months were linked to a 51% increase in the diagnosis of gestational diabetes (Nursing Times 2016).

Clearly, there is a need to develop better screening programs to ensure that pregnant people are properly diagnosed and only receive treatment when their blood sugar levels can pose a danger to themselves and their baby. The aim is to avoid any unnecessary treatment and distress during pregnancy (Vasileiou 2017).

Complications Following Gestational Diabetes

Post-delivery, both the mother and baby are at increased risk of developing type 2 diabetes later in life, with studies suggesting that mothers who have had GDM have a 50% chance of developing type 2 diabetes in the future (Healthdirect 2019).

Other potential complications include the development of hypertension and ischemic heart disease at a relatively young age compared to people without a previous diagnosis of GDM (Daly et al. 2018).

Should Screening be More Intensive?

Routine screening for GDM is recommended for all patients between the 26th and 28th week of pregnancy. This screening test, known as the glucose tolerance test (GTT), involves fasting for 8 to 12 hours, then taking three blood tests in three hours. The patient must consume a sugary liquid after the first test, then take the second test one hour later and the third test an hour after that. If the GTT finds that blood sugar levels are above what they should be, the patient is diagnosed with GDM (The Women’s 2013, 2020).

Studies suggest that despite the recommended timeframe for GTT, diabetes-related changes to the fetus may have already occurred by that time (Nursing Times 2016).

Whilst no differences were seen as early as 20 weeks gestation, there are calls for screening to start at 24 weeks, with increased monitoring of people with known risk factors from as early as the first trimester.

Daly et al. (2018) suggest that mothers with GDM are not only at greater risk of developing type 2 diabetes in the first year following birth but also for up to 25 years following birth.

Yet, following birth, less than 60% of people receive follow-up screening in the first year and less than 40% by the second year.

Is a change in practice needed?

Kampmann et al. (2015) suggest that it is, recommending that the way forward must also include greater interventions in the form of exercise, weight loss and a healthy diet.

With these additional support measures, there might then be an opportunity to break the circle that contributes to obesity, insulin resistance and type 2 diabetes.

Additional Resources



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Anne Watkins View profile
Anne is a freelance lecturer and medical writer at Mind Body Ink. She is a former midwife and nurse teacher with over 25 years’ experience working in the fields of healthcare, stress management and medical hypnosis. Her background includes working as a hospital midwife, Critical Care nurse, lecturer in Neonatal Intensive Care, and as a Clinical Nurse Specialist for a company making life support equipment. Anne has also studied many forms of complementary medicine and has extensive experience in the field of clinical hypnosis. She has a special interest in integrating complementary medicine into conventional healthcare settings and is currently an Associate Tutor, lecturing in Health Coaching and Medical Hypnosis at Exeter University in the UK. As a former Midwife, Anne has a natural passion for writing about fertility, pregnancy, birthing and baby care. Her recent publications include The Health Factor, Coach Yourself To Better Health and Positive Thinking For Kids. You can read more about her work at
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