Relationship between physical growth and motor development in infancy and early childhood: Multivariate analysis.

This study was based on a sample of 651 singleton infants, from 325 unrelated families. Body weight (WT), length (LT) and head circumference (HC) of each child were measured at day of birth and thereafter every 3 months during the first 2 years. The achievement of five developmental milestones was surveyed, the ages at which the infant could turn him- or herself over (TURN), sit up (SAT), stand up (STOOD), walk without support (WALK), and cut the first tooth (TOOTH). Principal component analysis showed several patterns, in particular: (1) PC1 includes all physical measurements of the infant at all specific ages, (2) PC2 is a factor of motor development and early growth rate; gestational age, birth weight, and body length also showed high negative correlations with this component, (3) PC4 is a factor that related the motor development variables with growth rate between 6 and 12 months, and (4) PC6 is a "late growth" component. Path analysis revealed that real relationships between the variables of motor development and growth rate are complicated. It showed the existence of direct relations between sequential motor milestones. However, most of the growth rate variables and birth measurements, in particular birth WT, had only an indirect contribution to rate of motor development. © 1993 Wiley-Liss, Inc.