Vitamin D supplementation and gross motor development: A 3-year follow-up of a randomized trial

Background: Vitamin D status during pregnancy, early childhood and season-at-birth are implicated in gross motor development (GMD).

Aim: To test whether vitamin D intake in infancy and season-at-birth affect GMD in early childhood.

Study design: 3-year follow up study of a single-center trial.

Subjects: Healthy infants (n = 116) were allocated to 400 (standard-of-care), 800 or 1200 IU/day of vitamin D3 supplementation from 1 to 12 months; n = 70 returned for follow-up at 3-years.

Outcome measures: The main outcome was GMD using the Peabody Developmental Motor Scales-2 which includes gross motor quotient (GMQ) and stationary, locomotion and object manipulation subtests.

Results: GMQ scores were normal (≥85) in 94 %. An interaction between dosage group and season-at-birth (p = 0.01) was observed for GMQ and stationary standardized score; among winter/spring born children, the 1200 IU/d scored higher vs. 400 and 800 IU/d groups. Object manipulation standardized score was higher (p = 0.04) in children in the 1200 vs. 400 IU/d group, without interaction with season-at-birth.

Conclusions: GMD in young children who received 400 IU/d of supplemental vitamin D in infancy is not influenced by season-at-birth. This dose of vitamin D of 400 IU/d as recommended in North America adequately supports GMD. The modest enhancement in GMD with 1200 IU/d in winter/spring born children requires further study.