Infant
Overview
Infant (嬰兒, infant) is a developmental-stage term generally referring to a child from 28 days after birth (the newborn period) through 12 months of age. International health statistics commonly classify 0–11 months as infants and 1–5 years as young children, while Korea's Infant and Toddler Care Act and Child Welfare Act group children under 6 years of age as "infants and toddlers (영유아)" and use this as a policy indicator. Infancy is the period in which the brain's neural networks and major body organs mature at the fastest rate in a lifetime, and nutrition, sleep, and attachment formation during this time lay the foundation for lifelong health and emotional development.
Key Details
Definition and Age Classification
- Newborn: from immediately after birth to 28 days of age
- Infant: from 1 month to under 12 months of age
- Young child (유아): 1 to 5 years of age (preschool)
- Infants and toddlers (영유아): a domestic policy term collectively referring to children under 6 years of age
In medical literature, "infancy" is sometimes broadly defined as the period from birth until the child can walk, roughly 12–15 months. Because developmental milestones vary greatly between individuals, they are used as reference indicators for screening rather than as absolute standards.
Physical Growth
Average weight at birth is about 3.0–3.4 kg and length about 50 cm. Weight doubles the birth weight by 4–5 months and triples it by around 12 months (about 9–10 kg), while length reaches about 75 cm at 12 months. Head circumference increases by about 12 cm during the first year, and the anterior fontanelle (the "soft spot") usually closes between 9 and 18 months. The first teeth begin to erupt around 6–10 months, starting with the lower front teeth.
Motor Development Milestones
- 2–3 months: head control, lifting the head when prone
- 6 months: rolling over, sitting with hands propped
- 8–9 months: crawling, pulling to stand holding an object
- 10–11 months: cruising sideways while holding onto furniture
- 12 months: standing alone, first steps
- 15 months: walking steadily on their own
Cognitive, Language, and Emotional Development
A social smile appears around 2 months, and babbling becomes active around 6 months. Object permanence (the understanding that objects continue to exist even when out of sight) develops between 8 and 12 months; stranger anxiety is common at 6–8 months and separation anxiety at 8–18 months. First words usually appear around 12 months, and by 18 months the child uses 10–20 words. According to Bowlby's attachment theory, consistent responsiveness from caregivers is central to forming secure attachment, which becomes the foundation for later social skills and emotional regulation.
Nutrition and Feeding
The World Health Organization (WHO) recommends exclusive breastfeeding until 6 months of age, followed by continued breastfeeding alongside complementary foods until 2 years. Breastfed infants are advised to receive vitamin D supplementation of 400 IU, and iron-rich complementary foods are needed after 6 months. Complementary feeding begins around 6 months, and the current standard is not to delay allergenic foods but to introduce them in small amounts from the start. After 12 months, the child transitions to regular cow's milk and family meals, but honey (risk of botulism under 1 year) and whole nuts or small bead-like foods (choking risk) require caution.
Sleep and Safety
Newborns sleep 16–18 hours a day, 6-month-olds about 14 hours, and by around 12 months 12–13 hours. To prevent sudden infant death syndrome (SIDS), recommendations include placing infants on their back to sleep, using a firm mattress, removing bumpers, cushions, and blankets, keeping the home smoke-free, and preventing overheating. At home, preventing drowning, falls, burns, and suffocation is important, and when traveling, a car seat appropriate for the child's age and weight must be used in a rear-facing position.
Health Care and Vaccination
Under the national immunization support program, BCG, hepatitis B, DTaP, polio, Hib, pneumococcal, and rotavirus vaccines are administered during infancy, and the first dose of MMR is given at 12–15 months. Infant health checkups are provided at 14–35 days (1st), 4–6 months (2nd), and 9–12 months (3rd) after birth, combining growth and developmental screening with oral examinations. Jaundice, febrile seizures, bronchiolitis (RSV), hand-foot-and-mouth disease, and otitis media are common conditions in infancy.
Recent Trends
In 2024–2025, Korea is in a phase of attempting a rebound from a total fertility rate in the 0.7 range, and the government continues to expand the parental benefit (1 million won per month for 0-year-olds, 500,000 won per month for 1-year-olds), infant allowances and childcare fee support, and care infrastructure for infants and toddlers. In the medical field, the introduction of monoclonal antibodies for RSV prevention (nirsevimab) and an RSV vaccine for pregnant women is spreading, strengthening strategies to prevent respiratory infections in infants. In addition, developmental screening and social-emotional assessment are being expanded in infant health checkups, and smart parenting devices that monitor sleep, crying, and body temperature along with AI-based developmental analysis services are becoming widespread, while WHO and pediatric society recommendations to minimize screen exposure for children under 2 years of age are being reemphasized. In the complementary food and formula market, regulations on low sugar and no additives and stronger ingredient labeling are under way.
Related Topics
- [[Newborn]]
- [[Young Child]]
- [[Childcare]]
- [[Breastfeeding]]
- [[Vaccination]]
- [[Child Development]]
- [[Low Birth Rate]]