Growth and development milestones from birth to adolescence
NCLEX-RN topic: Developmental stages and transitions
- Milestone: a skill 75% or more of children show by a certain age.
- Sit at 9 months, walk alone at 18, two words at 2.
- Losing a skill the child once had always needs follow-up.
- Act early on a missed milestone: screen and refer, don't wait.
- Birth weight about doubles by 5 months and triples by 1 year.
Key facts
- CDC milestones are skills most children (75% or more) can do by a given age.
- Losing a skill the child once had always needs follow-up, at any age.
- The AAP recommends general developmental screening at 9, 18 and 30 months and autism screening at 18 and 24 months.
Show all 7 key factsShow fewer
- Birth weight about doubles by 5 months and triples by 1 year.
- By 9 months most infants sit without support and look for a dropped object; by 18 months most walk without holding on.
- By 2 years most children put two words together; by 3 years most talk well enough for others to understand most of the time.
- Erikson: trust (infant), autonomy (toddler), initiative (preschool), industry (school age), identity (adolescent).
Quick check1 question · 2 more at the end
The nurse assesses a 9-month-old infant at a well-child visit. Which finding requires follow-up?
Correct answer: D.
CDC milestones are skills most children (75% or more) can do by a given age, so a missed milestone needs follow-up and screening. By 9 months most infants sit without support, babble sounds like "mamamama," and are shy or fearful with strangers. Walking alone is listed at 18 months and saying "mama" or "dada" as a name at 1 year, so their absence at 9 months is not yet a concern.
A Expected: shyness, clinginess or fear around strangers is a 9-month milestone.
B Expected: walking without holding on is an 18-month milestone.
C Expected: at 9 months infants babble; calling a parent "mama" or "dada" is a 1-year milestone.
D Correct: sitting without support is a 9-month movement milestone, so its absence needs follow-up.
Full lesson
Each part starts with its main idea. Open a part when you want the details.
The short answer: Developmental milestones are skills most children (75% or more) show by a certain age, such as sitting without support by 9 months and walking alone by 18 months. The nurse compares each child with these norms and acts early when a child misses a milestone or loses a skill, using screening and referral rather than waiting to see.
1 What counts as a developmental milestone?A milestone is a skill that most children, 75% or more, can do by a certain age. 1 min
A milestone is a skill that most children, 75% or more, can do by a certain age. That makes the milestone age a "most children by now" mark, not the earliest a child might show the skill. The CDC groups milestones into social and emotional, language, cognitive, and movement skills.
The rule for acting is simple. Act early if a child misses one or more milestones, loses a skill they once had, or a parent is worried. Share the concern with the provider, screen and refer. The AAP recommends general developmental screening at 9, 18 and 30 months and autism screening at 18 and 24 months.
2 What should a baby do in the first year?Infant skills build from head to toe and from the center of the body outward. 1 min
Infant skills build from head to toe and from the center of the body outward. Head control comes before sitting, sitting before crawling and pulling up, and walking comes last.
| By age | Movement | Social, language, thinking |
|---|---|---|
| 4 months | Holds head steady when held; pushes up on forearms | Coos; turns toward a voice |
| 9 months | Sits without support; rakes food; passes toys hand to hand | Shy or fearful with strangers; babbles "mamama"; looks for a dropped toy |
| 1 year | Pulls to stand; walks holding furniture; pincer grasp | Waves bye-bye; says "mama" or "dada"; understands "no" |
| 18 months | Walks alone; scribbles; tries a spoon | Tries 3 or more words; follows one-step directions |
| 2 years | Runs; kicks a ball; walks up a few stairs | Puts 2 words together; points to body parts |
| 3 years | Uses a fork; dresses partly alone | Holds a short conversation; mostly understood by others |
Growth follows its own rules. Birth weight about doubles by 5 months and triples by 1 year. By age 2, a child is about half of adult height. The posterior fontanelle closes by about 2 months and the anterior by about 18 months.
3 How do Erikson's stages shape nursing care?Erikson's stages tell the nurse what each age is working on emotionally, and care should support that work. 1 min
Erikson's stages tell the nurse what each age is working on emotionally, and care should support that work.
- Trust vs. mistrust (birth–1 year): meet feeding, comfort and warmth needs consistently.
- Autonomy vs. shame and doubt (1–2 years): toddlers test limits and say "no." Offer simple choices: "red cup or blue cup?"
- Initiative vs. guilt (3–5 years): let preschoolers do things "all by myself" through play.
- Industry vs. inferiority (6–11 years): school-age children value accomplishments and compare themselves with peers.
- Identity vs. role confusion (adolescence): teens try out roles and beliefs.
4 How do children think at each stage?Piaget's stages tell the nurse how to explain things so a child can understand. 1 min
Piaget's stages tell the nurse how to explain things so a child can understand.
- Sensorimotor (birth–2): learns through the senses; offer safe toys to touch and hear.
- Preoperational (2–7): thinks in symbols and play, with magical thinking. A preschooler may believe they caused an illness by misbehaving. Use simple explanations and reassure them it is not their fault.
- Concrete operational (7–11): thinks logically about real things; give factual explanations in plain words.
- Formal operational (about 12 and up): handles abstract ideas; include the teen in health decisions.
5 What the nurse doesThe nurse compares each child with age norms and acts early on any gap. 1 min
The nurse compares each child with age norms and acts early on any gap.
- Assess: at every well visit, compare the child's skills and growth with the norms for their age.
- Act: report a missed milestone or any loss of skills and support screening and referral to early intervention. Do not advise waiting to see.
- Teach: give parents age-matched guidance, such as offering a toddler choices.
Common mistakes
The traps students fall into most. Read these before you practice.
Watch out: A milestone age is the age most children have the skill, not the earliest age a child might show it.
Watch out: Stranger anxiety at 9 months is an expected milestone, not a bonding problem.
Watch out: Toddlers saying 'no' to everything reflects autonomy; offer simple choices rather than yes-or-no questions.
Watch out: Preschoolers may believe they caused an illness; reassure them it is not their fault rather than giving detailed medical explanations.
Watch out: Not being understood by strangers at age 2 is still within norms; that milestone is listed for age 3.
How to remember it
Two short hooks cover the milestone ages and Erikson's stages. Memory hook: "Sit at 9, walk at 18, two words at 2." For Erikson, the first five stages run T-A-I-I-I: Trust, Autonomy, Initiative, Industry, Identity.
Self-check:
- Name one movement and one social milestone expected by 9 months.
- A 20-month-old has stopped using the words she had at 15 months. What does the nurse do?
- How would you explain an IV start to a 4-year-old versus a 14-year-old?