Nutrition, Growth, and Development in Breastfed Infants
The Nutrition, Growth, and Development in Breastfed Infants domain tests human milk composition, nutrient requirements, growth patterns, and complementary feeding. Items often test what breast milk does and does not supply.
Milk composition
- Colostrum is low in volume but rich in secretory IgA, lactoferrin, leukocytes, and protein; it has a laxative effect that helps clear meconium.
- Mature milk is about 87% water, with lactose, fat, protein, oligosaccharides, enzymes, hormones, and growth factors. Fat content rises during a feed and varies by time of day.
- Human milk oligosaccharides are prebiotics that shape the infant microbiome. Secretory IgA, lactoferrin, lysozyme, and leukocytes provide immune protection.
- Foremilk and hindmilk are not separate milks; they describe fat concentration along a feed. Feeding to completion supports adequate energy intake.
- Breast milk supplies insufficient vitamin D, so exclusively and partially breastfed infants need 400 IU/day from birth. Vitamin K is given intramuscularly at birth. Iron stores last about 4-6 months; maternal B12 status matters for vegan mothers.
Growth and feeding
- Use WHO growth standards for breastfed infants. Expected newborn loss is up to 7-10%, with regain by 10-14 days. Average gain is about 20-30 g/day in the first months, then slows.
- Growth faltering is a sustained drop across centile lines, not one low weight. Assess intake, feeding effectiveness, health, and maternal factors.
- Start complementary foods at about 6 months, alongside continued breastfeeding. Offer iron-rich foods such as fortified cereal, meat, legumes, and eggs, plus vitamin C to aid iron absorption.
- Avoid honey before 12 months because of botulism risk, cow milk as the main drink before 12 months, and choking hazards. Introduce common allergens early and repeatedly when developmentally ready.
Worked example
A 6-month-old exclusively breastfed infant is growing along the 50th percentile. The mother asks whether formula is needed for iron. The reasoning: breast milk iron is low in absolute terms but has high bioavailability, and fetal iron stores are depleted around 4-6 months. The infant does not need formula; the plan is to start iron-rich complementary foods at 6 months and continue breastfeeding. A hemoglobin check is indicated only if there are risk factors or symptoms.
Traps that cost marks
- Saying breast milk lacks vitamin D and therefore needs no supplement; supplementation is required.
- Advising extra water for a breastfed infant under 6 months.
- Using CDC growth charts instead of WHO charts for breastfed infants.
- Treating a single low weight as growth faltering.
- Starting solids before 6 months without a medical reason.