CFB OGPAE02-2 Physiology Of Lactation, Breast Feeding And Infant Feeding (part II)

Term vs Preterm; Growth parameters (weight, length, head circumference); AGA vs SGA vs LGA; symmetrical vs asymmetrical SGA; LBW ( < 1.5 kg); ELBW ( < 1 kg) ^[1]

Day 0–4: fluid loss up to 7% of birth weight. Day 5–7: starts gaining weight. Fluid requirements increase and reach 150–180 ml/kg/day by day 7. ^[1]

Why this matters: Newborns are born with excess extracellular fluid. The initial physiological weight loss (up to 7% for term, up to 10–15% for preterms) reflects diuresis of this excess fluid. If weight loss exceeds 10% of birth weight, this is pathological and must be investigated.

• Day 0: fluid needs are very low (~60 ml/kg/day for term infants)
• Fluid needs escalate daily as renal function matures and insensible losses increase
• By day 7, target is ~150–180 ml/kg/day — this matches the volume of breast milk an exclusively breastfed infant should be receiving

11 weeks: fetal swallowing starts. 24 weeks: GIT anatomically completed. 28 weeks: GIT peristalsis. 33–36 weeks: coordinated suckling and swallowing. Functional development continues into infancy — digestion and absorption. ^[1]

Why coordinated suck-swallow matters: Premature babies < 33–34 weeks cannot safely coordinate sucking, swallowing, and breathing simultaneously. This is why they require gavage (tube) feeding and why oral feeds are only introduced once this coordination develops.

1. Achieve appropriate growth and development. 2. Compensate additional demand during disease state. 3. Prevent complications of nutritional deficiency or excess. ^[1]

Positive energy balance (gain) = intake > basal + expenditure. Expenditure includes activity, thermoregulation, digestion/metabolism, fecal loss, urine, heat loss by radiation and evaporation. Requirements: protein, fat, carbohydrates, minerals, vitamins, water. ^[1]

Normal infant growth is multifactorial: gestation, age, sex, ethnicity, feeding regimen, medical conditions, and even generational factors.

Protein: Preterms need more for growth. Whey protein (~60% in breast milk, 40% casein) — soluble upon acidification, easier digestion; contains essential amino acids, immunoproteins, and enzymes. ^[1]

Fat: 40–52% daily caloric intake; at least 3% total calories from linoleic acid. LC-PUFA important for growth, brain and retinal development. ^[1]

Carbohydrates: Glycogen stores from 2nd trimester, exhausted in 12–24 hours. Normal glucose utilization rate (GUR): 4–6 mg/kg/min (term), 4–8 mg/kg/min (preterm). ^[1]

Preterms: insensible water loss, catch-up growth, inadequate nutrient storage (glycogen, fat, calcium, iron, Vit D). Disease states: higher energy requirement. Fluid restriction in RDS/chronic lung/heart failure vs liberal in sepsis/NEC/IUGR. ^[1]

Respiratory quotient (RQ) = CO₂ elimination / O₂ consumed: Carbs (1.0), Protein (0.8), Fat (0.7). In chronic lung disease: restrict carbs, optimize fat and protein (lower RQ = less CO₂ production). ^[1]

Why RQ matters in chronic lung disease: These babies already have difficulty eliminating CO₂. Carbohydrate metabolism produces the most CO₂ per unit of O₂ consumed (RQ = 1.0). By shifting the caloric source to fat (RQ = 0.7), you reduce CO₂ production and ease respiratory burden.

Inborn errors of metabolism: dietary restrictions to avoid accumulation of harmful metabolites. ^[1]

Composition and volume adjusted to infants' growing needs. ^[1]

The composition of breast milk changes dynamically:

Key observations:

• Preterm milk is higher in energy, lipid, and protein than term milk — nature compensates for the premature baby's higher metabolic demands ^[1]
• Protein content decreases over the first month as growth velocity declines
• Lactose increases as the infant matures

Growth velocity and protein/fat accretion are highest at birth and decline with age. ^[1]

Mature human milk vs Enfamil (cow) vs Similac (cow) vs Isomil (soy) — per 100 Cal (i.e. 150 ml of 20 Cal/oz) ^[1]

Key exam points:

• Breast milk has the LOWEST renal solute load (14 mOsm) — gentler on immature neonatal kidneys ^[1]
• Breast milk has very low iron (0.05–0.075 mg) and Vit D (3 IU) — hence exclusively breastfed infants may need Vit D supplementation and iron supplementation after 4–6 months ^[1]
• Breast milk has a higher whey:casein ratio (80:20) than cow-based formulas — whey is more digestible ^[1]
• Formula has much higher iron and Vit D because of these known deficiencies in breast milk

Breastfeeding reduces risk of: Gastroenteritis (greatly reduced), respiratory illness, UTI, NEC, childhood leukaemia, CVD risk factors, ear infections, SIDS, diabetes, atopic disease. ^[1]

Dose-dependent relationship between BF duration and IQ score in young adulthood (Mortensen, JAMA 2002). PROBIT trial: first 12 months — lower risks of GI infections and eczema; follow-up at 6.5 years — higher WASI and academic performance scores. ^[1]

Preterm babies need: match intrauterine growth rate (15–20 g/kg/day), higher caloric requirement, prevention of NEC. ^[1]

Preterm formula tries to match growth needs: Whey/casein 60:40, higher calories (20–24 Cal/oz), higher protein, less lactose, MCT, higher Ca/PO₄ ratio, more vitamins. BUT preterm babies also need immature gut and immune system protection. ^[1]

Human milk in preterms provides: ↓ infection, 6.5-fold ↑ NEC in formula-fed (Lucas, Lancet 1990), protective dose > 50 ml/kg/day against late-onset sepsis, NEC prevention (Cochrane review). ^[1]

Benefits of human milk as trophic feeding: maturation/adaptation of premature GI tract, full enteral feeding achieved earlier, mothers who initiate lactation early more likely to sustain, psychological wellbeing, better neurodevelopmental outcomes (8-pt advantage at 8 years; higher visual acuity scores at 2–6 months; 5-point Bayley MDI increase per 100 ml/kg/day). ^[1]

For breastmilk-fed preterms < 1.5 kg: breastmilk fortification with human milk or formula fortifiers is recommended to optimize protein content. ^[1]

Problems: aggressive marketing + poor hospital policies. Solutions: Baby Friendly (Hospital) Initiatives. WHO International Code and national legislation. WHO/UNICEF Ten Steps to Successful Breastfeeding. ^[1]

The BFHI was launched by WHO/UNICEF in 1991 to ensure that all maternity facilities support breastfeeding. Key points:

• Hospitals should NOT distribute free formula samples (aggressive marketing from formula companies undermines breastfeeding)
• The WHO International Code of Marketing of Breast-milk Substitutes restricts formula advertising

Colostrum: contains all necessary nutrients, protects against infections, has a laxative effect, comes in small volumes. ^[1]

Why the laxative effect matters: Colostrum helps the newborn pass meconium, which contains bilirubin. Early meconium passage reduces enterohepatic circulation of bilirubin, helping to prevent neonatal jaundice.

Initiate BF within 1st hour, then exclusive BF for first 6 months. On-demand feeding. No bottles, teats, or pacifiers. Infants not exclusively BF need suitable breastmilk substitutes. At around 6 months: start safe and adequate complementary foods while continuing BF for up to 2 years and beyond. ^[1]

Encourage skin contact and early feeding after delivery. Kangaroo care. Value colostrum. Avoid unnecessary supplements and discourage teats/dummies. Avoid mother-baby separation. Encourage frequent feeding. Prescribe medications with care. Be supportive. Identify and care for "at-risk" babies (neonatal hypoglycaemia). ^[1]

Excess lactose in stool → loose, frothy, green stools and symptoms of colic. Low fat intake → inadequate intake of fat-soluble vitamins. ^[1]

Mechanism: During a feed, the initial milk (foremilk) is more watery and lactose-rich. As the feed progresses, fat content increases (hindmilk). If the baby doesn't feed long enough on one breast, or switches too quickly, they get excess foremilk (high lactose, low fat) → osmotic diarrhea from undigested lactose → green frothy stools. Solution: Let the baby finish one breast before switching.

Ineffective attachment and/or infrequent feeding → ↓↓↓ breast milk production → fail to sustain breastfeeding. ^[1]

Mechanism from first principles: Breast milk production is a supply-and-demand system. Prolactin drives milk synthesis; oxytocin drives milk ejection. Both are stimulated by suckling. If the baby doesn't attach well or doesn't feed frequently:

• Less nipple stimulation → less prolactin → less milk production
• Less milk removal → milk stasis → local feedback inhibitors (FIL = feedback inhibitor of lactation) accumulate → further ↓ production
• This creates a vicious cycle leading to lactation failure

Effective vs ineffective attachment: ineffective attachment → nipple soreness and cracks. ^[1]

Key signs of effective attachment: baby's mouth wide open, chin touching breast, lower lip turned outward, more areola visible above than below the mouth, audible swallowing.

Jaundice → lethargy → infrequent/inefficient feeds → reduced milk intake → fewer calories/less energy → reduced gut motility → re-absorption of bilirubin → reduced breastmilk supply → MORE jaundice. ^[1]

This vicious cycle diagram is extremely important and highly testable:

Jaundice → Lethargy → ↓ Feeding → ↓ Milk intake → ↓ Gut motility 
→ ↑ Enterohepatic circulation of bilirubin → ↑ Jaundice → More lethargy...

Management: Keep mother and baby together, frequent feeds, help from lactation consultant, express breastmilk and give (if necessary), AVOID WATER. ^[1]

Causes: ineffective attachment, infrequent/restricted feeding, underlying illness. Management: exclude underlying illness, keep mother and baby together, skilled help with attachment, frequent feeds, express breastmilk, monitor I/O and weight. ^[1]

Reliable parameters: weight, stools, urine, history of ineffective feeding. Unreliable parameters: dry skin and mouth / sunken fontanelle, serum sodium levels (in first few days), unsettled baby. ^[1]

Risk factors: Prematurity, SGA, compromised states (hypothermia, asphyxia, critically ill), maternal diabetes or beta-blocker therapy. Impaired counter-regulatory response; risk of neurological impairment if prolonged. ^[1]

Care: skin contact, early and regular feeds, warmth, close monitoring, colostrum. ^[1]

Why SGA babies are at risk: They have limited glycogen and fat stores, so when the transplacental glucose supply is cut at birth, they can't mount adequate gluconeogenesis or glycogenolysis.

Why infants of diabetic mothers (IDM) are at risk: Maternal hyperglycaemia → fetal hyperinsulinaemia (islet cell hyperplasia). After birth, the glucose supply stops but the high insulin levels persist → rebound hypoglycaemia.

"Transitional neonatal hypoglycaemia": The slide shows that normally breastfed babies may have low blood glucose in the first 24–48 hours but simultaneously mount ketone body production (an alternative fuel for the brain). This is a normal metabolic adaptation. The key is whether the baby is symptomatic and whether ketone production is appropriate.

1 Energy + 33 essential nutrients. Standards: WHO CODEX Alimentarius Commission Standards (Revised 2007); HK Food and Drugs Regulation 2014. ^[1]

Term: 110 kcal/kg/day (1st month), 95 kcal/kg/day (3–6m), 80 kcal/kg/day (6–12m). Preterm: 120 kcal/kg/day at 150 ml/kg/day. Preterm formulas: high protein, Ca, PO₄; additional Vit A, D, folate, zinc, iron; contains MCT, long-chain fats, glucose polymers, lactose. For BM-fed preterms < 1.5 kg, fortification recommended. Former preterms: enriched formula from discharge until 9–12 months corrected age. ^[1]

Why MCT in malabsorption: Medium-chain triglycerides (C6–C12) are absorbed directly into the portal circulation WITHOUT requiring bile salts for emulsification or chylomicron formation. They bypass the lymphatic system entirely. This is why they are ideal in:

• Cholestasis (bile salt deficiency)
• Chylothorax (lymphatic leak — LCT would worsen the chylous effusion)
• Short gut (reduced absorptive surface)

CRF/persistent hypercalcaemia: Renal formula (e.g. Similac PM 60/40) — low Ca, PO₄, K, iron. Cholestasis: MCT-enriched formula; most need fat-soluble vitamin supplementation (A, D, E, K). ^[1]

Why renal formula is low in these minerals: In CRF, the kidneys cannot excrete phosphate, potassium, etc. Excess calcium intake worsens hypercalcaemia. Low renal solute load protects fragile kidneys.

Why fat-soluble vitamin supplementation in cholestasis: Bile salts are needed for fat-soluble vitamin absorption. In cholestasis, bile flow is impaired → malabsorption of vitamins A, D, E, K.

CMPA: IgE or non-IgE mediated. Breastfeeding recommended if strong family history. Milk avoidance in maternal diet if BF-infants are symptomatic. ^[1]

Suitable formulas:

Unsuitable formulas for CMPA:

Boil water → clean surface/wash hands → sterilized bottle → fill with HOT WATER ≥ 70°C → add correct amount of powder → gently shake → cool → test temperature (lukewarm). ^[1]

Why ≥ 70°C? Powdered infant formula is NOT sterile. It can contain Cronobacter sakazakii (formerly Enterobacter sakazakii), which causes severe neonatal sepsis and meningitis. Water at ≥ 70°C kills these organisms while preserving most nutrients.

Complementary feeds "fill the gap" — BM alone insufficient to meet energy/nutritional needs. Gap widens as child grows. Slow/stop growing if gap not filled. Food types influenced by culture. By 2 years, breast milk entirely replaced by family foods. ^[1]

By 6 months corrected age, most achieve adequate maturation to start. ^[1]

Start with 1 food item. Gradual increase in consistency and variety. 6m: pureed/mashed/semi-solid. 8m: finger foods, self-feeding. 12m: family food, mature self-feeding. ^[1]

Feeding frequency: 2–3 times/day (6–8 months), 3–4 times/day (9–24 months), +1–2 nutritious snacks/day (12–24 months). ^[1]

Alternative approaches: "baby-led weaning" — infants share family food and self-feed with hand-held foods. ^[1]

Why avoid honey before 12 months: Clostridium botulinum spores can be present in honey. The infant's immature gut flora cannot outcompete these spores, leading to infant botulism — a potentially fatal flaccid paralysis.

Why avoid whole cow's milk before 12 months: Too high in protein and minerals (↑ renal solute load for immature kidneys), too low in iron and essential fatty acids, and high casein content is harder to digest.

Growth and body composition, neurodevelopment, gut microbiota establishment, immune-related disorders and infections, allergy, coeliac disease, T1DM, CVD. ^[1]

1. Which of the following is a contraindication to breastfeeding from the infant's side? → Galactosaemia
2. A premature baby at 32 weeks is noted to have NEC. Which feeding practice most reduces NEC risk? → Human milk feeding
3. Breast milk is low in which two nutrients, necessitating supplementation? → Iron and Vitamin D
4. A mother with CMPA infant asks about goat milk formula. What do you advise? → Not suitable; 90% cross-reactivity
5. When should complementary feeding be introduced? → Around 6 months corrected age
6. What is the recommended water temperature for preparing powdered infant formula? → ≥ 70°C

1. List 4 benefits of breastfeeding for the infant. (Protection against GI infections, NEC prevention in preterms, neurodevelopmental benefits, reduced atopic disease)
2. A preterm infant of 28 weeks requires enteral nutrition. Describe the formula considerations. (Higher protein, Ca, PO₄; MCT; LC-PUFA; 120 kcal/kg/day; fortifier if using expressed breast milk < 1.5 kg)
3. Describe the vicious cycle of jaundice in breastfed neonates and management. (Jaundice → lethargy → ↓ feeding → ↓ gut motility → ↑ enterohepatic circulation → ↑ jaundice. Manage: keep together, frequent feeds, express BM, avoid water)