They were as follows: being at 3 to 9 months' corrected age, gestational age of less than 36 weeks + 6 days, birth weight of 2000 g or less. Infants with any genetic, metabolic, orthopedic congenital abnormalities or chronic diseases and parents' rejection to participate in the study were excluded.

They were as follows: being between 3 and 9 months of age, being full-term, had no complications during delivery. Infants that presented any type of sensory or motor disorder were excluded.

This cross-sectional study included LBW and NW infants at between 3 and 9 months of age. The levels of trunk control were investigated by using the Segmental Assessment Trunk Control (SATCo). The Alberta Infant Motor Scale (AIMS) were used for assessment of gross motor performance and identify typical and atypical motor development of infants.

The gross motor performance of infants were preliminarily evaluated with the Alberta Infant Motor Scale (AIMS). The AIMS, an observational assessment scale, assesses the infants between 0 and 18 months and measures gross motor maturation in infants from birth through independent walking. The AIMS has 58 items, which assess three aspects of motor performance--weight-bearing, posture and antigravity movements in the positions of supine, prone, sitting, and standing positions. A typically developing 18-month-old infant can perform all movements and will obtain a total score of 58. Gross motor performance is defined by the AIMS total score, which is expressed in percentiles based on age. AIMS total score categories were determined by using normative percentile ranges. The categories of gross motor performances were defined as follows: 0-10 atypical development, 11-25 suspected performance, 26-75 normal performance, 76-90 very good performance, 91-100 excellent performance.

The infants were evaluated by using the Segmental Assessment Trunk Control (SATCo). SATCo is the only valid instrument that can assess the level of trunk control by segments and assess the ability of the typical or neuromotor deficient infant to maintain or recover a vertical position while sitting. The infant was positioned in a sitting posture on a wooden bench with the pelvis maintained in a neutral position using a belt system in relation to the vertical axis and with the head upright to identify the level of trunk control. 0 and 1 scores were given according to maintenance of upright posture and the total score was calculated.