Infancy (1 month to 12 months) is the period of the fastest growth and development after birth. The infant moves from reflex behavior to intentional action, from crying to first words, and from total dependence to early independence. Health promotion focuses on nutrition, responsive caregiving, developmental surveillance, immunization, and injury prevention.

Physical growth

A healthy infant follows their own percentile curve on the growth chart; a single measurement is less meaningful than the trend.

Developmental milestones (CDC "Learn the Signs. Act Early." 2022 revision) — each is a skill that most children (75% or more) show by that age, so a missing milestone is a reason to screen, not a normal variation to ignore.

• Crawling is not a milestone in the revised checklists — many infants scoot, roll, or commando-crawl, and some go straight to pulling up. An infant who is not yet crawling at 9 months but sits alone and moves toward objects is usually developing normally
• Growth follows cephalocaudal and proximodistal order: head control → sitting → standing; whole-hand (palmar) grasp → raking → pincer grasp
• Corrected age is used for preterm infants

Cognitive (Piaget — sensorimotor): primary circular reactions (1–4 months) → secondary circular reactions (4–8 months; repeats an action to see an interesting effect, like shaking a rattle) → coordination of schemes (8–12 months; intentional goal-directed behavior; object permanence — searches for a hidden toy). Throwing toys and watching them fall is exploration of cause and effect.

Psychosocial: trust vs. mistrust (Erikson); oral stage (Freud) — mouthing hands and objects is normal exploration. Stranger anxiety appears at about 6–9 months and separation anxiety at about 8 months, peaking in the second year — both are signs of healthy attachment (Bowlby).

• Growth measurements at each well visit (weight, length, head circumference) plotted on WHO growth charts (birth to 2 years)
• Developmental screening with a standardized tool at 9 months (and ongoing surveillance at every visit)
• Hemoglobin or hematocrit around 12 months (iron deficiency screening); lead screening per risk or local policy (US: required at 12 and 24 months for Medicaid-enrolled children)
• Hearing and vision surveillance; red reflex at every visit
• Oral health risk assessment; fluoride varnish applied in primary care from the first tooth

Nutrition

• Exclusive breastfeeding for about the first 6 months, then continued breastfeeding with complementary foods to 2 years or beyond; iron-fortified infant formula when not breastfeeding
• Vitamin D 400 IU daily for breastfed and partially breastfed infants, starting soon after birth; also formula-fed infants taking less than about 1 L (32 oz) of formula per day
• Iron: exclusively breastfed term infants should receive iron supplementation (about 1 mg/kg/day) from about 4 months until iron-rich foods are eaten. Drops can stain teeth (give behind the teeth, then wipe or brush), stools turn dark, and constipation is common; give between feeds, not with milk. Iron overdose is a leading cause of serious poisoning in young children — store out of reach
• Vitamin D drops: measure with the dropper supplied; excess can cause hypercalcemia
• Complementary foods at about 6 months when developmentally ready: good head control, sits with support, opens mouth for a spoon, loss of the tongue-thrust (extrusion) reflex
  • Start with iron-rich foods (meat, iron-fortified cereal, legumes), then vegetables, fruits, and other foods
  • Introduce one new single-ingredient food at a time and watch for reactions
  • Early introduction of allergenic foods (peanut in a safe form such as thinned peanut butter, egg) around 4–6 months is recommended; infants with severe eczema or egg allergy should be discussed with their clinician (who may choose testing or supervised introduction) — do not delay introduction
  • Progress in texture: purées → mashed → soft finger foods (around 8–9 months) → family foods
• Avoid before 12 months: honey (infant botulism), cow's milk as the main drink (low iron, GI blood loss, high renal solute load), fruit juice, added salt and sugar
• Choking hazards: whole grapes, nuts, popcorn, hot-dog rounds, hard raw vegetables, large pieces of meat or cheese
• No bottle propping and no bottle in bed (early childhood caries, aspiration, ear infections); introduce a cup around 6 months and wean from the bottle by about 12–18 months (ideally close to 12 months)

Dental care

• Wipe gums; brush teeth from the first tooth with a smear (rice-grain size) of fluoride toothpaste; first dental visit by 12 months (dental home)
• Teething: firm, cool (not frozen) teething rings; do not use topical benzocaine or lidocaine teething gels (methemoglobinemia, seizures) and avoid amber necklaces (strangulation, choking)

Listed in priority order.

1. Injury prevention matched to motor skills (the leading preventable threat)
   • Falls: never leave an infant alone on a bed, sofa, or changing table — rolling begins around 4–6 months; stair gates when mobile
   • Suffocation: safe sleep (see Sudden Infant Death Syndrome and Safe Sleep)
   • Choking and aspiration: remove small objects (anything that fits through a toilet-paper tube), latex balloons, and button batteries
   • Car seats: rear-facing in the back seat, never in front of an active airbag
   • Drowning and burns: never leave the infant alone in the bath, even for a moment; set water heater at 49 °C (120 °F) or lower and test bath water; no hot drinks while holding the infant
   • No baby walkers (falls down stairs, access to hazards; do not speed walking)
2. Support head and neck when holding young infants — head control is incomplete before about 4 months
3. Monitor growth and development at each contact; screen and refer missed milestones or loss of skills
4. Promote responsive feeding and attachment: recognize hunger and fullness cues; respond consistently to crying; encourage skin-to-skin contact, talking, reading, and eye contact
5. Immunizations on schedule (see Immunizations)
6. Prevent abusive head trauma: teach that crying peaks around 6–8 weeks and that it is safe to put a crying baby down in the crib and step away briefly; never shake
7. Developmental stimulation: supervised tummy time while awake, several times daily; age-appropriate toys (mobiles and rattles, then stacking cups, push toys, board books); peek-a-boo supports object permanence

• Development: expect a wide normal range; missed milestones or lost skills need screening rather than reassurance alone
• Mouthing hands and objects at 4–6 months is normal oral exploration
• Screen time: avoid digital media (except video chatting) before about 18–24 months; interaction with people and real objects is what builds learning
• Sleep: about 12–16 hours per 24 hours including naps from 4–12 months; bedtime routine; always back to sleep
• Stranger and separation anxiety are normal — brief goodbyes, consistent caregivers, and a comfort object help
• Pacifiers are acceptable; do not coat them in honey or sugar
• Keep poison control and emergency numbers visible

• No social smile by about 2–3 months; no head control by 4 months; not rolling or reaching by 6 months; not sitting alone or babbling by 9 months; not pulling to stand, no gestures, or no response to name by 12 months
• Loss of previously acquired skills at any age
• Persistent primitive reflexes; persistent fisting or strong early hand preference before 12 months
• Faltering growth (failure to thrive) — weight falling across percentiles; poor feeding
• Head circumference crossing percentiles (hydrocephalus or microcephaly) or early fontanel closure
• Bruises, burns, or fractures in a non-mobile infant — consider maltreatment and follow reporting rules
• Iron-deficiency anemia from excess cow's milk or low-iron diet

• Weight doubles by 5–6 months, triples by 12 months; length +50% by 12 months
• Posterior fontanel closes by 2 months, anterior by 12–18 months
• First tooth about 6 months; teeth ≈ age in months − 6
• CDC 2022: head steady 4 months; rolls tummy to back 6 months; sits without support 9 months; pulls to stand, cruises, pincer grasp 12 months
• Crawling is not a required milestone
• Object permanence — looks for dropped or hidden objects around 9 months
• Secondary circular reactions (4–8 months): repeats actions for effect (shaking a rattle)
• Stranger anxiety 6–9 months; separation anxiety from about 8 months; trust vs. mistrust
• Exclusive breastfeeding ~6 months; vitamin D 400 IU; complementary foods at ~6 months, iron-rich first
• No honey, cow's milk, or juice before 12 months; no bottle in bed
• No baby walkers; rear-facing car seat; never leave on elevated surfaces
• No teething gels with benzocaine or lidocaine