Karyotype — Cri-du-Chat 46,XX,del(5p)

A 3-year-old girl presents to the pediatric clinic with developmental delay, severe speech impairment, and a history of a distinctive high-pitched cry in infancy that has now resolved. On examination, she has microcephaly, round facies, widely spaced eyes, and low-set ears. Her karyotype is shown in the diagram. The structure marked **A** represents the chromosomal abnormality responsible for her clinical presentation. Which of the following is the MOST characteristic clinical feature that would have been noted in the neonatal period due to this deletion?