Randomization
As it is well known that lower gestational age and mother's education level affect neurodevelopment adversely, we stratified participants based on gestational age at birth (32—28 weeks, below 28 weeks) and the mother's educational level (primary, elementary, and bachelor's degree). Randomization was provided by the closed envelope method. Three voluntary physical therapists took part in the study. They made a random allocation sequence, enrolled participants, assigned participants to interventions, and collected data.