[CG] Gestational diabetes (GDM), diagnosing, Clyde

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Criteria for diagnosing Gestational Diabetes (GDM) Clyde

At booking: assess for the following risk factors. If one or more is present, check HbA1c and book OGTT at 26 weeks’

  • BMI ≥35kg/m2
  • Previous baby ≥4.5kg
  • Family history of T1 or T2 diabetes in a first degree relative (child, parent,
    brother, sister)
  • Family origin: South Asian, Middle Eastern, Chinese or Black African/ Caribbean
  • Previous pancreatitis
  • Previous gestational diabetes (book OGTT at 16 and 26 weeks’)

Result of HbA1c taken at booking:

  • If ≥ 48mmol/mol refer directly to the diabetes antenatal clinic
  • If < 48mmol/mol perform OGTT at 26 weeks’ gestation (NB if previous GDM for OGTT at 16 weeks’ also)

During pregnancy: arrange OGTT if any of the clinical factors below are present:

  • glycosuria of 2+ or above on 1 occasion
  • glycosuria of 1+ or above on 2 or more occasions
  • Polyhydramnios
  • EFW ≥97th centile

Escalation of OGTT result:

If fasting blood glucose (FBG) ≥7.0mmol/l and/or 2hr blood glucose ≥ 11.0mol/l, refer immediately to the local Diabetes Specialist Nurse. This applies at any gestational age and women should be seen urgently.

End date for OGTT:

Do not perform OGTT after 35+0 weeks. If there is a clinical concern of GDM at ≥35+0 weeks’ perform a random blood glucose (RBG) and HbA1c. Refer to the DSN/Diabetes Clinic if RBG ≥9mmol/l or HbA1c ≥39mmol/mol.

The utility of OGTT in this cohort of women is unproven but high blood glucoses need to be excluded.

OGTT is positive for GDM if FBG ≥5.1mmol/l and/or 2-h BG ≥8.5mmol/l

Last reviewed: 22 November 2021

Next review: 01 April 2022

Author(s): R Maitland

Version: 2

Document Id: 828