Timing, duration, and severity of iron deficiency in early development and motor outcomes at 9 months

Background/objectives Poorer motor development is reported in infants with iron deficiency (ID). The role of timing, duration and severity is unclear. We assessed relations between ID timing, duration, and severity and gross motor scores, neurological integrity, and motor behavior quality at 9 months. Subjects/methods Iron status was determined at birth and 9 months in otherwise healthy term Chinese infants. The 9-month motor evaluation included the Peabody Developmental Motor Scale (PDMS-2), Infant Neurological International Battery (INFANIB), and motor quality factor. Motor outcomes were analyzed by ID timing (fetal-neonatal, infancy), duration, and severity. For severity, we also considered maternal iron status. Results The data were available for 1194 infants. Iron status was classified as fetal-neonatal and infancy ID (n = 253), fetal-neonatal ID (n = 256), infancy ID (n = 288), and not ID (n = 397). Compared with not ID, infants with fetal-neonatal or infancy ID had lower locomotion scores (effect size ds = 0.19, 0.18) and those with ID in both periods (longer duration) had lower locomotion and overall PDMS-2 gross motor scores (ds = 0.20, 0.18); ID groups did not differ. More severe ID in late pregnancy was associated with lower INFANIB Vestibular function (p = 0.01), and total score (p = 0.03). More severe ID in infancy was associated with lower scores for locomotion (p = 0.03), overall gross motor (p = 0.05). Conclusions Fetal-neonatal and/or infancy ID was associated with lower overall gross motor development and locomotion test scores at 9 months. Associations with ID severity varied by ID timing: more severe ID in late pregnancy, poorer neurological integrity; more severe ID in infancy, poorer gross motor development.