Introduction Iron deficiency (ID) is a major cause of morbidity in pregnancy. Antenatal clinics use a hemoglobin to screen for ID, which delays the diagnosis of subclinical ID. The aim of this study was to investigate the clinical utility of the percentage of microcytic red cells (%Micro-R), percentage of hypochromic red cells (%Hypo-He), and reticulocyte hemoglobin content (Ret-He) on the Sysmex hematology analyzer in pregnant patients. Methods Results For this study, 102 nonanemic patients in the first trimester of pregnancy presenting for the first time to antenatal clinic were screened for ID. There were 50 (49.02%) patients with ID as defined according to iron studies. The independent t test and receiver operating characteristic (ROC) analysis were applied. There was a significant difference in the Ret-He, %Micro-R, and %Hypo-He between the ID and non-ID groups (P < 0.001). The area under curve (AUC) for the Ret-He (0.81, 95% CI 0.71-0.88) indicates that the Ret-He at a cutoff ID (P < 0.0001). The AUC of %Hypo-He (0.78, 95% CI 0.69-0.86) was not superior to the mean cell hemoglobin (0.78, 95% CI 0.69-0.86). The %Micro-R (0.79, 95% CI 0.70-0.87) showed improved diagnostic accuracy compared to mean cell volume (0.75, 95% CI 0.65-0.83). Conclusion The new reticulocyte and erythrocyte parameters are reliable tests for the diagnosis of subclinical ID in pregnant patients. Further studies, however, are required to confirm the diagnostic utility of the erythrocyte parameters in pregnant patients. These tests will benefit the management of pregnant patients attending antenatal clinic.