Objective To clarify the impact of pre-and postnatal iron deficiency on children's motor development.Methods This was a longitudinal follow-up study.A total of 114 infants (58 boys,56 girls) born from April 2010 to December 2011 in Fuyang district of Hangzhou were enrolled.Based on cord blood and 9-month iron status,subjects were divided into prenatal iron deficiency (34 children),postnatal iron deficiency (37 children) and non-iron deficiency group (43 children).Peabody Developmental Motor Scale and BOT2-simplified version were used to evaluate the motor capacity in infants and preschoolers at 9 months,18 months and 5 years,respectively.Hierarchical linear modeling (HLM) was used to investigate the trajectory of motor development with age,the influence of different timing of early iron deficiency on children's motor development,and the differences (adjusted for possible confounding factors) in motor development in children with pre-or postnatal iron deficiency or non-iron deficiency in different family educational environment.Results At the age of 9 months,18 months and 5 years,107,109,and 114 children were evaluated respectively.After controlling for a variety of confounding factors,it was found that children with prenatal iron deficiency had significantly lower scores of motor development compared with non-iron deficiency children (52.04 vs.54.05 scores,β =-2.01,P=0.007),and that children with postnatal iron deficiency had similar scores of motor development compared with non-iron deficiency children,showing no significant difference (53.07 vs.54.05 scores,β=-0.98,P=0.180).Regardless of the maternal education status,prenatal iron deficiency children always had lower motor scores than non-iron deficiency children (49.86 vs.52.15 and 49.58 vs.51.58 scores,β=-2.29,-2.00;P=0.031,0.049).Among the non-iron deficiency children,those whose mothers had a higher education level had higher motor scores compared with those whose mothers had a lower education level (52.45 vs.50.46 scores,β=1.99,P=0.035).Conclusions The motor development of children with prenatal iron deficiency did not catch up with their counterparts without iron deficiency by 5 years of age.The results indicate the importance of preventing iron deficiency in the fetus.