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Achieving developmental milestones on time is a cornerstone of healthy, normal development. As physicians, we expect children to achieve certain milestones by specific times. These milestones include gross motor and fine motor skills, expressive and receptive language, vision, hearing, and cognitive and social skills. Although it may seem clear-cut by which age a child should be able to perform each skill, there is some flexibility. It is important to keep in mind whether a skill should be achieved by 50% of kids by a certain age or by 90% of kids at a certain age. In this chapter, we discuss skills in terms of when 75% to 90% of typical children of that age should have achieved the skill.1-8
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When tracking development, providers should correct the age to account for premature birth (birth prior to 37 weeks’ gestational age) until a child is 2 years old.9,10
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DEVELOPMENTAL MILESTONES
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Gross Motor: The Moro startle, where a baby’s head falls backward and they reflexively extend the arms and legs outward and then rapidly bring arms to midline, lasts until 2 to 3 months old. The plantar grasp reflex, where the infant’s toes curl downward when you touch the sole of the foot behind the toes, is present from birth until 6 months old. The fencing reflex (also called asymmetrical tonic neck reflex) lasts until 5 to 7 months old; in this reflex, when a baby’s head is turned to one side, the baby will reflexively straighten the arm on that side and flex their opposite arm. The Babinski reflex, where stroking the sole of the foot triggers the big toe to extend upward and other toes to fan outward, is present and can persist until 9 to 12 months old. In the stepping reflex, when a baby is held upright with soles touching the floor, they reflexively step one leg forward; this reflex is present from birth until 2 months old.
Fine Motor: The newborn grasp reflex (also called palmar grasp), where stroking the palm of the baby’s hand triggers the baby to grip the finger, is present and lasts until 5 to 6 months old. Newborns preferentially hold hands fisted much of the time.
Language/Oral Skills: A newborn baby cries when there is discomfort. When an object touches the roof of their mouth, the sucking reflex triggers the baby to suck. Until 4 months old, when a baby’s cheek or mouth is stroked on one side, they will turn their head to that side due to the rooting reflex.
Social: A newborn baby maintains brief periods of wakefulness.
Vision: A newborn can see 8 to 10 inches away from their face and is very sensitive to bright lights. Their vision is only in black, white, and gray.
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