Monitoring

A postnatal test is essential to check for persisting hyperglycaemia. Unfortunately rates of postpartum screening for diabetes mellitus in women with a history of GDM are low, with fewer than half of women receiving screening.[3][51][62][135]​​ Studies suggest that there are multiple reasons for this, such as transportation, childcare arrangements, type of medical insurance (in countries where this applies), and lack of understanding of the risks of diabetes.[62]

Guidelines differ in their exact follow-up recommendations for women with GDM whose blood glucose levels have returned to normal after the birth. Check your local protocol.

In the UK, the National Institute for Health and Care Excellence (NICE) recommends the following:[4]

  • For women diagnosed with GDM whose blood glucose levels have returned to normal after the birth:

    • Offer lifestyle advice (including weight control, diet, and exercise) - including providing support to lose weight if overweight and to lose any excess gestational weight gained

    • Offer a fasting plasma glucose (FPG) test or haemoglobin A1c (HbA1c) 6 to 13 weeks after the birth to exclude diabetes (for practical reasons this can take place at the 6-week postnatal check or baby’s immunisation visit)

    • Do not routinely offer a 75-g 2‑hour oral glucose tolerance test (OGTT).

It is increasingly commonplace to favour HbA1c over FPG as the postnatal test of choice. It is more convenient as it does not require a prolonged fast, it can be done at any time of day, and general practitioners are very familiar with using it to diagnose and treat type 2 diabetes.

Advise the woman as follows based on the results of the postnatal test:[4]

  • FPG <6.0 mmol/L (<108 mg/dL) OR HbA1c <39 mmol/mol (<5.7%): there is a low probability she has diabetes at that moment but she has a moderate risk of developing it in the future. She should continue to follow lifestyle advice and have annual HbA1c testing.

  • FPG 6.0 to 6.9 mmol/L (108-124 mg/dL) OR HbA1c 39-47 mmol/mol (5.7% to 6.5%): she is at high risk of developing type 2 diabetes. Offer evidence-based advice, guidance, and interventions on preventing type 2 diabetes through diet and exercise changes and offer a referral to the NHS Diabetes Prevention Programme.

  • FPG ≥7.0 mmol/L (≥126 mg/dL) OR HbA1c >48 mmol/mol (>6.5%): she is likely to have type 2 diabetes. Offer confirmatory testing.

Other guidelines recommend OGTT postnatal testing rather than FPG or HbA1c. The European Society of Cardiology and American Diabetes Association (ADA) recommend OGTT 4-12 weeks postnatally for all women with GDM.[3][117]​ The American College of Obstetricians and Gynecologists recommends that OGTT can be undertaken either at 4-12 weeks postpartum or in the immediate postpartum period (during the delivery hospitalisation), the latter option having demonstrated improved engagement in testing.[62]

  • For any woman with a history of GDM, ensure annual screening for cardiovascular disease and type 2 diabetes.

  • If in the UK, offer a referral to the NHS Diabetes Prevention Programme.[4][136][137]

Women with GDM have a higher risk of cardiovascular events postnatally that is independent of the development of type 2 diabetes.[130] In one UK population-based retrospective cohort study, women with a history of GDM had nearly twice the risk of developing hypertension and were diagnosed with ischaemic heart disease at a younger age compared with women without prior GDM.[138] The American Heart Association recognises prior GDM as a cardiovascular risk factor, highlighting the opportunity for early cardiovascular risk surveillance and intervention.[130][139]​​ 

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