Families often first notice 16p12.1p12.3 triplication syndrome when a baby has low muscle tone that makes feeding or holding up the head harder than expected, or when early motor milestones like rolling and sitting come later than peers. As toddlers grow, speech delay, learning differences, and developmental delays become clearer, and some children have small head size, distinctive facial features, or shorter height that prompts a genetics referral. Doctors may first confirm the diagnosis after noticing a pattern of delays and features, or during prenatal/early childhood chromosomal microarray testing done because of ultrasound findings, growth concerns, or developmental evaluations—these are the most common first signs of 16p12.1p12.3 triplication syndrome.