['One obstacle to providing early intervention to infants with myelomeningocele (MMC) is the challenge of quantifying impaired neuromotor control of movements early in life.', 'We used the nonlinear analysis tool Approximate Entropy (ApEn) to analyze periodicity and complexity of supine spontaneous lower extremity movements of infants with MMC and typical development (TD) at 1, 3, 6, and 9 months of age.', 'Movements of infants with MMC were more regular and repeatable (lower ApEn values) than movements of infants with TD, indicating less adaptive and flexible movement patterns. For both groups ApEn values decreased with age, and the movements of infants with MMC were less complex than movements of infants with TD. Further, for infants with MMC, lesion level and age of walking onset correlated negatively with ApEn values.'] Do approximate entropy values demonstrate impaired neuromotor control of spontaneous leg activity in infants with myelomeningocele?