The objective of our study was to investigate the zinc (Zn) status and effects of Zn supplementation in relation to insulin-like growth factor-I (IGF-I), iron deficiency anemia and outcome of birth weight of newborn in pregnant women. The role of Zn and IGF-I in hematological abnormalities has remained unclear. Twenty-four Japanese women, when examined at the second trimester of pregnancy, had hemoglobin concentrations (Hb) below 11.0 g/dl and almost normocytic indices. We compared the hematological status and serum IGF-I levels before and after Zn supplementation. While Hb and RBC did not change, IGF-I and total iron binding capacity (TIBC) were increased significantly, and concentrations of erythropoetin were increased, but not statistically significant. There were significant positive correlations between increases in RBC and increases in IGF-I and TIBC in the Zn administration. Birth weights of newborn under 2500 g whose mother received zinc were 4.2%, against 7.1% in controls. Zn status to some extent can account for IGF-I and hematological abnormalities and the outcome of birth weight of the newborn in pregnant women.