Recently, it has become clear that mild abnormal glucose tolerance increases the incidence of perinatal maternalinfant complications, and so the definition and diagnostic criteria of gestational diabetes mellitus(GDM) have been changed. Therefore, in patients with GDM and pregnant women with diabetes mellitus, even stricter glycemic control than before is required to reduce the incidence of perinatal maternal-infant complications. Strict glycemic control cannot be attained without an indicator of glycemic control; this review proposes a reliable indicator. The gold standard indicator of glycemic control in patients with diabetes mellitus is hemoglobin A1c(Hb A1c); however, we have demonstrated that Hb A1 c does not reflect glycemic control accurately during pregnancy because of iron deficiency. It has also become clear that glycated albumin, another indicator of glycemic control, is not influenced by iron deficiency and therefore might be a better indicator of glycemic control in patients with GDM and pregnant women with diabetes mellitus. However, largepopulation epidemiological studies are necessary in order to confirm our proposal. Here, we outline the most recent findings about the indicators of glycemic control during pregnancy including fructosamine and 1,5-anhydroglucitol. Recently, it has become clear that mild abnormal glucose tolerance increases the incidence of perinatal maternalinfant complications, and so the definition and diagnostic criteria of gestational diabetes mellitus (GDM) have been changed. Thus, in patients with GDM and pregnant women with diabetes mellitus, even stricter glycemic control than before is required to reduce the incidence of perinatal maternal-infant complications. Strict glycemic control can not be attained without an indicator of glycemic control; this review proposes a reliable indicator. The gold standard indicator of glycemic control in patients with diabetes It has also become clear that glycated albumin, another indicator of glycemic control, is not affected by iron deficiency and therefore might a better indicator of glycemic control in patie However, largepopulation epidemiological studies are necessary in order to confirm our proposal. Here, we outline the most recent findings about the indicators of glycemic control during pregnancy including fructosamine and 1,5-anhydroglucitol.