Introduction: Gestational diabetes occurs in more than 8% of all pregnancies and is associated with an increase in the number of adverse pregnancy outcomes, such as macrosomia, dystocia, cesarean delivery, and maternal mortality. Regarding this, the present study was conducted to investigate the relationship between hemoglobin levels in the first trimester of pregnancy and the incidence of gestational diabetes mellitus in patients referring to healthcare centers in Zabol, Iran, in 2017.

Materials and Method: This case-control study was conducted on pregnant women referring to the healthcare centers of Zabol. The participants were selected through convenience consecutive sampling technique. The study population corresponded to a group of females aged 18-40 years with a singleton pregnancy and the gestational age of less than 12 weeks based on the first day of the last regular menstruation. The subjects did not have hypertension, cardiac and renal disorders, diabetes, and hereditary hemoglobinopathy (e.g., thalassemia and sickle cells anemia). The data were analyzed in SPSS (version 22) using Chi-Square and t-test.

Results: The mean age and mean body mass index the participants were 29.28±10.8 years and 59.44±34.7 kg/m², respectively. Out of 80 samples, 40 cases were diagnosed with gestational diabetes, and the others 40 were healthy. The diabetic group had a higher hemoglobin level (13.42±1.4) as compared to that of the non-diabetic patients (12.1±0.68), which was significantly different between the two groups (P<0.001).

Conclusion: The elevation of iron level can increase insulin production and secretion. Moreover, it can enhance the lipid oxidation, thereby reducing glucose consumption in the muscles and increasing glucose production in the liver. This mechanism makes the person susceptible to gestational diabetes by inducing insulin resistance. According to this study, high maternal hemoglobin can be considered as an independent risk factor for diabetes.