Gestational diabetes: postnatal testing and long-term risk
The case
A 29-year-old woman with gestational diabetes managed by diet alone delivers a 3.6 kg infant at 39 weeks by normal vaginal birth without complications. She is discharged at 48 hours. She asks when she should be tested for diabetes after the pregnancy and what her long-term risk is. Which of the following most accurately describes the postnatal management and long-term risk?
Options
- AOral glucose tolerance test at 6 to 12 weeks, then regular testing
- BNo testing; gestational diabetes carries no later risk
- CHbA1c at discharge is sufficient
- DAnnual glucose testing starting next year
- ETest only if symptoms develop
Think it through before you read on. Which single option is best, and why are the other four wrong?
Show the answer and explanation
Answer
A. Oral glucose tolerance test at 6 to 12 weeks, then regular testing
Why this is the right answer
Gestational diabetes usually resolves after the placenta is delivered, but it marks a woman as high risk for type 2 diabetes for the rest of her life. Around half of women with gestational diabetes develop type 2 diabetes within 10 to 20 years, and the risk of recurrence in a future pregnancy is also high.
For this reason every woman with gestational diabetes needs a postnatal test. The Australasian Diabetes in Pregnancy Society and the RACGP diabetes handbook recommend a 75 g oral glucose tolerance test at 6 to 12 weeks after birth. This identifies women whose glucose has not returned to normal, some of whom have undiagnosed type 2 diabetes or impaired glucose tolerance that needs immediate management.
After a normal postnatal test, ongoing screening continues for life: an HbA1c or fasting glucose every 1 to 3 years, and testing before any future pregnancy, with early testing again in that pregnancy. Australian pathology requests for the postnatal test can be linked to the National Gestational Diabetes Register, which sends reminders.
HbA1c is not used immediately after birth because pregnancy and blood loss change red cell turnover and make it unreliable until about 3 months postpartum.
The postnatal visit is also the time for lifestyle advice: healthy weight, physical activity and breastfeeding, all of which lower the risk of progression to type 2 diabetes.
Why the other options are wrong
- B
Gestational diabetes carries roughly a 50% lifetime risk of type 2 diabetes.
- C
HbA1c is unreliable in the early postpartum period; an OGTT or fasting glucose is required.
- D
Waiting a year misses women with persistent hyperglycaemia who need treatment now.
- E
Type 2 diabetes is usually silent in its early years; symptom-triggered testing is too late.
High-yield takeaway
After gestational diabetes: a 75 g OGTT at 6 to 12 weeks postpartum, then lifelong screening every 1 to 3 years and before each future pregnancy.
Reference: ADIPS Consensus Guidelines / RACGP Management of Type 2 Diabetes: A Handbook for General Practice (2025 / 2020)
Common questions
Why not an HbA1c straight after delivery?
Pregnancy and blood loss change red cell turnover, so HbA1c is unreliable until about 3 months after birth.
What is the long-term risk after gestational diabetes?
Around half of women develop type 2 diabetes within 10 to 20 years, so screening continues for life.
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