Maternal serum ferritin and gestational impaired glucose tolerance

OBJECTIVE - To determine if the reported features of decreased iron store in the infant of diabetic mother are related to underlying maternal iron deficiency, a prospective case-control study was performed on a group of low-risk antenatal patients without preexisting anemia or thalassemia trait and before the diagnosis of gestational diabetes mellitus (GDM) in the last trimester. RESEARCH DESIGN AND METHODS - At the time of routine screening for anemia and GDM at 28-30 weeks of gestation, an additional blood sample was collected for the assay of serum ferritin, iron, and total iron binding capacity (TIBC). Patients with elevated random sugar underwent a 75-g oral glucose tolerance test (OGTT), interpreted by the World Health Organization criteria. For each person diagnosed with GDM, a control subject matched in maternal age and parity was identified, and their iron status and hematological indexes were compared. RESULTS - There were 60 patients with gestational impaired glucose tolerance (GIGT), and none had frank GDM. There was no difference in the hematological indexes or serum iron and TIBC values, but serum ferritin level was significantly increased in the GIGT group, when compared with control subjects. CONCLUSIONS - The findings indicate that there was no evidence of preexisting iron deficiency in the third trimester before the diagnosis of GIGT, while serum ferritin was even increased in the GIGT patients, a phenomenon that could have reflected the glucose intolerance. Serum ferritin is probably an unreliable index for maternal iron therapy in these patients, and the role of iron therapy in GIGT patients remains to be established.