The World Health Organization uses the term “infant” in its recommendations on feeding, vaccination, and the management of malnutrition. The word does not always cover the same age range depending on the document consulted, which generates frequent confusion among health professionals, parents, and national institutions.
Newborn, infant, young child: the age categories used by WHO
WHO documents do not rely on a single classification. Several subcategories coexist, each linked to a specific medical or nutritional context.
- The newborn corresponds to the neonatal period, which lasts from birth until the 28th day of life. This phase accounts for a high proportion of infant mortality and is subject to specific care protocols.
- The infant under 6 months appears in recommendations on exclusive breastfeeding and in protocols for managing acute malnutrition. WHO separates this group from that of children aged 6 to 59 months.
- The young child usually refers to a child under 2 years old in texts about infant and young child feeding, where WHO recommends continuing breastfeeding until 2 years or beyond.
Thus, the 6-month limit is not a boundary beyond which a child ceases to be an infant. It marks the recommended start of complementary feeding while continuing breastfeeding.
To delve deeper into the definition of infant according to WHO, it is important to keep in mind that the reference framework changes depending on whether we are discussing nutrition, pharmacology, or clinical pediatrics.
Infant in France: why the definition varies according to the reference framework
In France, common usage and the regulatory framework do not coincide with WHO categories. The dictionary of the Académie française defines an infant as a child over three weeks and under two years old. The etymology refers to the Latin nutricio (nourishment, education): the word primarily designates the period of feeding at the breast or bottle.
ANSM, which evaluates pediatric medications, uses its own age classes to adapt dosages and clinical trials. These ranges do not overlap with those of WHO or the definition in common language.
Presenting a single age range as universal would therefore be a mistake. The term infant does not have the same significance depending on whether one reads a WHO document, a medication leaflet, or an article on childcare. Before comparing two sources, checking the reference framework used helps avoid misunderstandings.
Exclusive breastfeeding and complementary feeding: the WHO framework up to 2 years
WHO and UNICEF recommendations structure the feeding of infants and young children around three stages.
Initiating breastfeeding within the hour following birth constitutes the first stage. Exclusive breastfeeding for the first six months of life forms the second. The third begins at 6 months with the introduction of safe and appropriate complementary foods while continuing breastfeeding until 2 years or beyond.
This sequence is based on nutritional and epidemiological data. WHO estimates that nearly 400,000 deaths of children under 5 could be prevented each year if all infants were exclusively breastfed for the first six months and if this breastfeeding continued until 2 years or beyond.
Malnutrition remains a major factor: half of child deaths are attributable to it. In 2024, 150 million children under 5 were stunted, 43 million were wasted, and 36 million were overweight.
Why the 6-month limit is functional, not definitional
A common misunderstanding is to believe that an infant “becomes” a young child at 6 months. In reality, this threshold signals a change in feeding practices, not a change in status. The child remains an infant well beyond 6 months in most classifications, including those of WHO when it addresses extended breastfeeding.
The category “infants under 6 months” exists to isolate a group whose nutritional needs are met solely by breast milk. Beyond that, management protocols change, but the term infant does not disappear from the texts.
Growth and health of the infant: what professionals monitor
Monitoring the infant is organized around weight gain, psychomotor development, and vaccination coverage. WHO growth curves, used in many countries, serve as a reference to identify stunting or insufficient weight gain.
Key nutrients during this period include iron, whose reserves built up during pregnancy gradually deplete. The introduction of iron-rich foods starting at 6 months meets this physiological need. Insufficient iron intake increases the risk of cognitive development disorders.
Infant health checks are not limited to weighing. Assessing reflexes, tone, vision, and hearing is part of the mandatory examinations in France. These consultations allow for the early detection of anomalies that parental monitoring alone may not always identify.
The distinction between different age ranges (newborn, infant, young child) is not just a vocabulary exercise. It conditions care protocols, medication dosages, and nutritional alert thresholds. A treatment suitable for an 18-month-old child is not necessarily appropriate for a 3-month-old infant, even if both sometimes share the same name in common language.
