Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy, affecting approximately 10–15% of pregnancies in Australia. Early detection and coordinated management are essential for reducing maternal and fetal risks- and general practitioners (GPs) play a crucial role in this process.
Why Universal Screening Matters
While known risk factors such as elevated BMI, polycystic ovary syndrome (PCOS), a history of GDM, or a family history of diabetes increase likelihood of GDM, It can also occur in women without any identifiable risk factors.. For this reason, universal screening between 24 to 28 weeks’ gestation is recommended, as relying solely on risk factors would miss a significant proportion of cases.
Recommended Screening Protocol
Australia follows the 75g oral glucose tolerance test (OGTT) in line with the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria, based on data from the HAPO (Hyperglycemia and Adverse Pregnancy Outcome) study.
- The OGTT is performed between 24 and 28 weeks’ gestation and involves:Overnight fasting
- Fasting glucose test
- Glucose drink (75g)
- Blood tests at Fasting, 1 and 2 hours post-load
Diagnosis is made if any of the following thresholds are met:
- Fasting: ? 5.1 mmol/L
- 1 hour: ? 10.0 mmol/L
- 2 hour: ? 8.5 mmol/L
Post-diagnosis Management
- Patients diagnosed with GDM should be referred to a multidisciplinary antenatal care team for comprehensive support, including: Obstetric monitoring
- Diabetes education (via accredited diabetes educators)
- Dietitian support
- Blood glucose self-monitoring
- Pharmacological therapy (metformin or insulin), if indicated
While many patients can achieve glycaemic targets with diet and exercise alone, 20–30% of cases may require insulin therapy to optimize blood glucose control. .
Complications of Poorly Controlled GDM
Untreated or poorly controlled GDM increases the risk of:
- Preeclampsia
- Macrosomia and shoulder dystocia
- Neonatal hypoglycaemia
- Preterm birth and operative delivery
However, with timely diagnosis and appropriate management, most pregnancies can proceed safely to term with good maternal and neonatal outcomes.
Postpartum Follow-Up and Long Term Risk
At 6-12 weeks postpartum, women should undergo a repeat OGTT to assess for persistent glucose intolerance. Patients with prior GDM have a 7–10-fold increased risk of developing type 2 diabetes in the future.
Ongoing follow -up should include:
- Lifestyle advice and weight management
HbA1c or fasting glucose testing every 1-3 years
Conclusion
GPs are central to both early detection and long term care of patients with GDM. Adhering to screening guidelines and ensuring timely referrals can significantly reduce perinatal complications and long-term metabolic risks for both mother and child.
References
- Australasian Diabetes in Pregnancy Society (ADIPS). Guidelines for the testing and diagnosis of gestational diabetes mellitus in Australia. 2020. Available from: https://adips.org
- McIntyre HD, Gibbons KS, Lowe J, North R. Diagnosis and management of gestational diabetes: summary of updated NICE guidance. BMJ. 2020;369:m1315. doi:10.1136/bmj.m1315
- Zhu Y, Zhang C. Prevalence of gestational diabetes and risk of progression to type 2 diabetes: a global perspective. Curr Diab Rep. 2016;16(1):7. doi:10.1007/s11892-015-0699-x
- Metzger BE, Lowe LP, Dyer AR, Trimble ER, Chaovarindr U, Coustan DR, et al. Hyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008;358(19):1991–2002. doi:10.1056/NEJMoa0707943
- Farrar D, Simmonds M, Bryant M, Sheldon TA, Tuffnell D, Golder S, et al. Treatments for gestational diabetes: a systematic review and meta-analysis. BMJ. 2017;356:i3960. doi:10.1136/bmj.i3960
- Billionnet C, Mitanchez D, Weill A, Nizard J, Alla F, Hartemann A, et al. Gestational diabetes and adverse perinatal outcomes from 716,152 births in France in 2012. Diabetologia. 2017;60(4):636–644. doi:10.1007/s00125-017-4206-6
- Kim C, Newton KM, Knopp RH. Gestational diabetes and the incidence of type 2 diabetes: a systematic review. JAMA. 2022;327(11):1075–1083. doi:10.1001/jama.2022.1577
