Objectives: Different forms of anemia are considered as the most frequent complication of the gestational period. By its etiology, pathogenesis, and clinical hematology, it is not a single disease. Among all forms of anemia occurring during pregnancy, iron deficiency anemia (IDA) is the most common, accounting for 80–95% of all cases. Design: The article describes a theoretical basis for the diagnosis of the anemic syndrome among pregnant women, the determining factors of its development, and the diagnostic methods at different gestational periods. Participants/Materials, Setting, and Methods: Diagnostic and prognostic values of iron balance indicators in the body were established for IDA during pregnancy to improve the outcome of childbirth. A total of 140 anemic patients were examined. The control group consisted of 50 pregnant women without anemia and other significant health problems, 48 IDA pregnant women, and 42 pregnant women with anemia caused by various chronic diseases, including rheumatoid arthritis. All patients of the main and control groups were registered on clinical records at the Family Planning Center in Aktobe city, Kazakhstan. Results: Ferrokinetic indicators were suggested for diagnosing IDA and anemia of chronic diseases. It was established that IDA is characterized by low ferritin levels during gestation, while increased ferritin and C-reactive protein are typical for anemia of chronic diseases. Limitations: Differential diagnostics was applied for pregnant women with IDA and anemia of chronic diseases to observe the dynamics of serum ferritin and C-reactive protein (CRP) levels at different gestational periods. The article presents the results of a study on ferrokinetics in pregnant women with IDA and anemia caused by inflammation or chronic diseases. Other causes of anemia leading to a decrease in hemoglobin (Hb) levels to <90 g/L include hemoglobinopathies, which were not considered in this study. Conclusions: Determination of iron deficiency in pregnant women at different gestational periods will allow for identifying the risk group of anemic patients and deciding on the treatment. IDA (Hb <100 g/L) can be effectively measured by ferritin level <15 ng/mL, iron level of <11.5 μmol/L, and transferrin level >2.6 mg/L at p < 0.001. Anemia due to chronic diseases (Hb <100 g/L) can be effectively diagnosed with ferritin above 15 μg/L and CRP above 10 mg/L at p < 0.001.