The study discussed the physiological changes of pregnancy in Sudanese pregnant women the study aimed to assess the effect of pregnancy in Red blood cell, Packed Cell Volume (PCV) and hemoglobin among Sudanese pregnant women, and to correlate the PCV as an indicator of hemodilution in different trimesters among Sudanese women using or not using iron and folic acid supplement. The researcher used across sectional study which applied on 300 pregnant women presented to Port-Sudan obstetrical Hospital for antenatal care from 2019 to 2020. The samples were collected with Chemically clean and sterile disposable needles, syringes and swab were used for all blood samples, 4.5 mL of blood was collected from each participant into a tube containing the anticoagulant Ethylene Diamine Tetraacetic Acid (EDTA), gently mixed the tube five to six times A full blood count was performed using Hematological analyzer (Sysmex XP 300). The study found out that 90 women in each trimester of pregnancy (first, second and third) the mean value of Hemoglobin (Hb) in pregnant women was 11.3±1.4 g/dl, 11.4 ±1.4 g/dl and 10.3±1.2 g/dl in 1st, 2nd and 3rd trimester respectively. The study also found out that the mean value of PCV was 33.35%. Moreover, Hb was lower during 3rd trimester compared with 1st (hemodilution). The cut off level for anemia in Sudanese non pregnant females could be even lower than 11g/dl as the normal level was found to be lower than the international one. Due to hemodilution anemia in pregnancy is considered if Hb less than 9g/dl. The study recommends that diagnosis of anemia should be revised during pregnancy as this study has shown Hb level less than 9g/dl (66%) can be the cut off level.