Background & Objectives: Studies on relationships between maternal hemoglobin (Hb) level and adverse pregnancy outcomes have been inconsistent. The aim of this study was to examine the birth outcomes in pregnant women with normal hemoglobin level in the first trimester. Methods: In this study, 108 healthy pregnant women with GA=10-14 weeks and Hb≥11g/dl were selected by cluster random sampling and followed till delivery. In addition to medical history and clinical examination, Hb test were performed at the end of first, second, and third trimesters and their association with birth outcomes were investigated. Statistical analyses were performed using SPSS software. Results: The prevalence of anemia at second and third trimester were 27.9%, 12.7%, respectively. Hb concentration of 29.1% in second trimester and 5.8% in third trimester were higher than 13.2 g/dl. There were positive correlations between birth weight and the second (p=0.02) and third trimesters’ Hb concentrations (p=0.03). Moreover, the Apgar score of less than 8 significantly increased in women with Hb<11g/dl and Hb>13.2g/dl in the second trimester (p<0.001). Conclusion: Our findings demonstrated that abnormal concentrations of Hb in second and third trimesters increased the risk of adverse birth outcomes in terms of LBW and low Apgar scores, so the control of Hb at these times is recommended.