What results on glucose tolerance testing (GTT) support a diagnosis of gestational diabetes mellitus?

Updated: May 10, 2021
  • Author: Jiun-Lih Jerry Lin, MBBS, MS(Orth); Chief Editor: Eric B Staros, MD  more...
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In a 75 g oral GTT, a diagnosis of gestational diabetes mellitus is made if one or more of the following glucose levels is elevated:

  • Fasting: ≥92 mg/dL (5.1 mmol/L),

  • One hour: ≥180 mg/dL (10 mmol/L),

  • Two hour: ≥153 mg/dL (8.5 mmol/L)

The diagnostic criteria for 0-, 1-, and 2-hour values were chosen to identify the same risk of an adverse fetal outcome at each time point. [14]

Unless contraindicated, women in the postpartum period with gestational diabetes mellitus should have another GTT, usually at 6–12 weeks. [13]  They should also have regular ongoing surveillance as there is an increased risk of recurrence in future pregnancies and an increased risk of developing type 2 diabetes mellitus.

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