Table 10.

Gestational diabetes mellitus: its definition and diagnostic criteria

Definition	Gestational diabetes mellitus (GDM) is defined as a state of pre‐diabetic impaired glucose tolerance (IGT) identified or occurring for the first time during pregnancy, but it does not include overt diabetes in pregnancy or pre‐gestational diabetes mellitus.
Gestational diabetes mellitus (GDM)	GDM is diagnosed if one or more of the following criteria have been met in a 75 g OGTT: ① Fasting blood glucose value ≥92 mg/dL ② 1‐h post‐OGTT glucose value ≥180 mg/dL ③ 2‐h post‐OGTT glucose value ≥153 mg/dL
Diagnostic criteria for overt diabetes in pregnancy (ODM)*1	Overt diabetes in pregnancy is diagnosed if ① or ② below has been met: ① Fasting blood glucose value ≥126 mg/dL ② HbA1c ≥6.5% Women with casual/post‐OGTT blood glucose ≥200 mg/dL should be examined to see if they meet ① or ② above, with the potential diagnosis of overt diabetes in pregnancy in mind*2.
Pre‐gestational diabetes mellitus	① Diabetes mellitus diagnosed before pregnancy ② Pregnancy associated with unequivocal evidence of diabetic retinopathy

*1 Overt diabetes in pregnancy includes diabetes overlooked before pregnancy, impaired glucose tolerance due to changes in glucose metabolism during pregnancy and type 1 diabetes occurring during pregnancy. In either case, the diagnosis needs to be confirmed in affected women after delivery.

*2 Women are expected to show higher post‐OGTT glucose values during pregnancy, particularly later pregnancy, than usual, reflecting increased physiological insulin resistance during pregnancy. Thus, the casual blood glucose and 75 g OGTT values defined in the diagnostic criteria for diabetes mellitus are not readily applicable.

These diagnostic criteria are intended for use during pregnancy and any diagnosis made based on these criteria requires to be assessed after delivery based on the ‘diagnostic criteria for diabetes’ ¹⁵ .