Abstract

Background. Muscle tone in preterm infants (PTI) is often reduced due to maturation-related hypotonia. As intrauterine and extrauterine environments vary, the maturation of muscle tone at 40 weeks of corrected gestational age (CGA) may also differ. This study aims to compare muscle tone development in extreme PTI, very PTI, and moderate to late PTI at birth and to compare PTI of various gestational ages with full-term infants (FTI) at 40 weeks of CGA.

Methods. This observational study was conducted with 132 infants based on specific criteria after obtaining informed consent. Muscle tone in PTI of various gestational ages was measured using the Amiel-Tison angle (ATA) at birth. They were reassessed for muscle tone at 40 weeks of corrected gestational age. Muscle tone in FTI was also assessed using ATA at birth.

Results. ANOVA and post hoc analysis of the three groups showed a significant difference in muscle tone among extreme PTI, very PTI, and moderate PTI at birth for all angles (p < 0.05). ANOVA of the three PTI groups and FTI showed a significant difference between the groups (p < 0.05), except for the dorsiflexion angle between moderate PTI and FTI at 40 weeks of corrected age.

Conclusions. The significant differences in muscle tone among PTI of various gestational ages at birth and between PTI and FTI at 40 weeks of CGA emphasize the need for addressing tonal deviations appropriately based on gestational age to enhance motor development.

Key words

Amiel-Tison angle, maturation-related hypotonia, muscle tone, preterm infants