Development. The 9-month-old is all about exploring, with no awareness of safety. He/she will be “into everything,” while frequently turning back to check in with a parent. To assess development, start by asking the parents what new skills they have noticed. He/she has mastered independent sitting and pivoting. The baby should be able to readily transition from sitting to lying and lying down to sitting up. Many 9-month-olds will navigate using a four-point crawl; however, some may “commando” crawl, using their arms to pull themselves forward while remaining prone. This may be a prelude to a traditional four-point crawl, but because traditional crawling is not considered a “mandatory” milestone, be sure to assess for abnormal upper body weakness, hypotonia, or spasticity as a reason for not crawling. Since the advent of “Back to Sleep,” (the recommendation that infants sleep supine has resulted in over a 50% decrease in the incidence of sudden infant death syndrome since 1992.) more children are progressing to standing and cruising before crawling. These motor milestones correlate with increasing myelination of the central nervous system and cerebellar growth.¹ Some will be pulling to stand and may be cruising on furniture, but all 9-month-olds should be able to bear their full weight when held in standing. Manipulating objects with the hands and mouthing are the principal methods of learning in this oral motor phase of development. Though not yet verbal, the child can communicate likes and dislikes clearly using facial gestures and sounds. In the cognitive domain, there is definite stranger awareness; however, the degree of stranger anxiety manifested by each infant will vary. Object permanence, or understanding that people and things exist that are not currently in sight, has begun to develop. Test for this by hiding a toy under a cloth, and watch the child find it.¹ The 9-month-old loves social interaction and will participate in peek-a-boo and patty-cake. There should be polysyllabic babbling and nonspecific uttering of mama and dada. Repetition will help children make more sounds. A child’s inflections start to mimic spoken language.¹ A 9-month-old can wave goodbye, respond to his/her name, and begin to understand “no.” Certain emotions, such as happiness and frustration, will be more evident.² The infant may be starting to gesture using the arm, and this will evolve into discrete pointing with an isolated index finger. Simultaneously the grasping of a small object may now be a gross raking motion with progression to a mature pincer grasp using precise finger-thumb apposition. He/she will hold the bottle, and bang two held objects together.

In addition to developmental surveillance, the American Academy of Pediatrics (AAP) recommends administration of a formal developmental screening tool at the 9-month visit. Developmental red flags include absence of babbling or localization to sound, lack of weight bearing, and absence of a bonded relationship with parents and caregivers.