Background Late achievement of motor milestones may increase the risk of overweight since early achievers have increased possibility to build lean body mass and expend energy. Further overweight infants may have delayed achievement of gross motor milestones as the overweight may limit mobility. The aim of this paper was to investigate whether delayed ability to sit and walk is associated with BMI at age seven and whether increasing weight at birth and at 5 months of age postpone the achievement of motor milestones.
Methods We examined whether timing of achievement of motor milestone (ability to sit and walk independently) predicted later overweight or later increase in Body Mass Index (BMI=weight (kg)/height2 (m)) z-scores and we examined whether increasing birth weight and increasing BMI at 5 months predicted later achievement of motor milestones The associations were analysed in a dataset of 32 973 children participating in the Danish National Birth Cohort. Mothers were recruited in the period 1996–2002 and follow-up took place during 2003 to 2010. We used logistic and linear regression analysis.
Results At age 7 years, a total of 10% of the children were overweight including 1.5% obese. Late ability to sit (>8 months) and to walk (>15 months) was not associated with overweight at age seven (OR's between 1.00; (CI 0.98 to 1.02) and 1.02; (CI 0.95 to 1.07)). Although statistically significant, the results from linear regression showed very weak inverse associations between later achievement of the ability to walk and sit (in months) led to a reduced BMI at age seven for both boys and girls. Similarly, birth weight and weight at 5 months was weakly associated with achievement of the ability to walk and sit, slightly stronger in boys than in girls.
Conclusions We conclude that that delayed motor development is neither a predictor of nor a risk factor for childhood overweight and that birth weight and BMI at age 5 months do not predict delayed motor development.