The primary defect is a retrognathic mandible which occurs at 7-11 weeks of gestation due to abnormal development of the first pharyngeal arch (see branchial apparatus). May present with upper airway obstruction, sleep disturbance or apnoea. Robin sequence occurs in 1 in 8500 neonates 3. Robin sequence is the preferred term rather than Pierre Robin syndrome, as most cases are not syndromic 4.
