Iron deficiency, with or without anemia, is common in pregnant women and more than half of the anemia’s in the world are due to the deficiency of iron in the serum. The aims of this study were to determine the percentage and level of serum iron among iron supplemented pregnant women in different trimesters and in different age groups among supplemented pregnant women in Sulaimani city. This study was carried out in the private clinic in the Sulaimani city-Kurdistan Region of Iraq. The pregnant women were participated and enrolled between the first of December 2018 and first of December 2019. Two hundred and seventy-five healthy and iron supplemented pregnant women were selected randomly and the questionnaire form, which contains information about age of mothers and their gestational age, was filled and serum iron level was measured by COBAS C111 analyzer. The results of this study found that the percentage of iron deficiency among participants was high 33%, 45%, and 52.6 % in the first trimester in different age groups <25, 25–35, and above 35 years old, respectively. However, in the third trimesters decreased to 12.5%, 7.1%, and 3.7% in <25, 25–35, and above 35 years old, respectively. Regarding serum iron levels, the present study found that there were significant differences between ages 25 and 35 with age <25 years. However, there was no significant difference between first, second, and third trimesters. This study concludes that the percentage of iron deficiency among supplemented pregnant women was high compared to other cities or other countries. Pregnant women who their ages <25 are at risk of serum iron deficiency. On the other hand, pregnancy trimesters had no effects on the serum iron level among supplemented pregnant women.