Bilateral upper-limb palsy of the newborn infant: Taxonomy, differential diagnosis, and clinical pathways.

Bilateral reduction or absence of upper-limb movement in a newborn infant is a rare but critical presentation that cannot be anchored on the unilateral paradigm of brachial plexus birth injury (BPBI). Bilaterality substantially widens the differential to include cervical spinal cord injury, neuromuscular disorders, and non-neurological movement limitation; thus, default attribution to bilateral BPBI risks missing a serious central pathology. No standardized terminology or investigation framework currently addresses this phenotype. This review introduces bilateral upper-limb palsy of the newborn infant (BULPN) and proposes a three-category taxonomy separating 'true BULPN' (bilateral plexus-level palsy at birth) from mimics and acquired (postnatal-onset) palsy. True BULPN is most consistently reported in breech delivery and it is frequently asymmetric; published cohorts describe a high burden of concurrent phrenic nerve palsy. A localization-first diagnostic algorithm and time-anchored, severity-stratified management pathways are presented to support safer and more targeted clinical assessment and management, and reduce the risk of misdiagnosis.