CFB OGPAE02-1 Physiology Of Lactation, Breast Feeding And Infant Feeding (part I)
Lactation physiology encompasses the hormonal mechanisms of mammogenesis, lactogenesis, and galactopoiesis, along with the principles of breastfeeding initiation and infant nutritional requirements in the early postnatal period.
Physiology of Lactation, Breast Feeding and Infant Feeding – Part I
Lecture Map
This lecture is fundamentally about why breast milk is the ideal food for infants, how the breast makes and delivers milk (the physiology), what goes wrong (breast problems during lactation), and what to think about when prescribing drugs to a breastfeeding mother. It bridges O&G (puerperium, maternal health) and Paediatrics (infant nutrition, growth, infection prevention). Everything connects back to five principles of infant feeding, and the physiology explains why breastfeeding satisfies all five.
- Principles of infant feeding
- Benefits of breast feeding (infant, mother, socioeconomic)
- Promotion of breast feeding (blocks, WHO 10 steps)
- Physiology of lactation (anatomy, initiation, maintenance, weaning, ovulation suppression)
- Breast problems (sore nipples → engorgement → blocked ducts → mastitis → abscess)
- Medication during breast feeding
This is a CFB (Clinical Foundation Block) lecture delivered under the O&G-Paediatrics curriculum. It is tested in the Fourth Summative and has appeared in MCQ format (see 2023 Q38 on Sheehan syndrome/lactation failure, 2025 Q9 on breast engorgement management) [8][9]. Expect questions on:
- Physiology of the milk production and let-down reflexes
- Contraindications to breastfeeding
- Differentiating engorgement vs blocked duct vs mastitis vs abscess
- Drug safety principles during lactation
- Lactational amenorrhoea criteria
1. Principles of Infant Feeding
There are five core principles of infant feeding. Breast milk satisfies all five. [1]
| # | Principle | Why It Matters |
|---|---|---|
| 1 | Adequate nutrition for homeostasis, growth and development | Infants grow faster than any other stage of life – 20% of energy intake goes to growth alone. Deficiency → failure to thrive, brain damage |
| 2 | Food easily digested and absorbed | The neonatal GI tract is immature (no teeth, low gastric acid, low pancreatic enzymes). Food must be compatible with this limited digestive capacity |
| 3 | Clean source of food, prevention of infection | In developing countries, gastroenteritis from contaminated formula is a leading cause of infant death. Infection also raises energy requirements, creating a vicious cycle with malnutrition |
| 4 | Minimise early exposure to foreign protein → prevent atopy | The immature gut is more permeable. Early exposure to cow's milk protein increases risk of eczema, asthma, and allergic disease in genetically predisposed infants |
| 5 | Special requirements for preterm infants, metabolic diseases, and other conditions | One size does not fit all – preterm infants need more energy and specific nutrients; galactosaemia infants cannot have lactose |
Energy requirement: ~110 kcal/kg/day for infants 0–12 months [1]
- ~20% for growth, remainder for basal metabolism, thermoregulation, and activity
- Compare with adults: only ~40 kcal/kg/day (sedentary)
- Nitrogen requirement: 120 mg/kg/day in infants (similar to adults at 100 mg/kg/day, but per-kg it's higher – reflecting greater protein synthesis for growth)
| Age Group | kcal/kg/day | Nitrogen (mg/kg/day) |
|---|---|---|
| 0–12 months | 110–85 | 120 |
| 1–3 years | 95–85 | 120 |
| 3–12 years | 85–60 | 110 |
| Adult (sedentary) | 40 | 100 |
Why does this matter clinically? If you miscalculate an infant's caloric needs or if feeds are inadequate, growth faltering (failure to thrive) happens rapidly because reserves are small and demand is proportionally huge. [1][2]
Specific amino acids (taurine, cysteine) and fatty acids (LC-PUFA, MCT) in breast milk are critical for brain and retinal development [1]
Carbohydrate:
- Main energy source (lactose is the predominant carbohydrate in breast milk)
- Lactose also promotes calcium absorption and supports healthy gut flora
Protein:
- Growth and tissue repair
- Taurine: deficiency causes irreversible retinal damage (demonstrated in growing kittens) – breast milk is rich in taurine
- Cysteine: newborns lack the enzyme to convert methionine → cysteine, so cysteine is an essential amino acid for neonates (it's conditionally essential). Breast milk provides it directly
Fat:
- Energy-dense (9 kcal/g) and supplies essential fatty acids
- LC-PUFA (long-chain polyunsaturated fatty acids): DHA and ARA are critical for brain and retinal development
- MCT (medium-chain triglycerides): absorbed more easily because they don't require bile salts for emulsification – important for the immature neonatal GI system
- Fat in breast milk is encased in lipase-containing membranes → self-digesting, making it easier to absorb than cow's milk fat [1]
Minerals and vitamins:
The newborn's digestive system is not fully developed [1]
- No teeth, low gastric acid, low pepsin, low pancreatic lipase and amylase
- Casein curds form in the stomach and are harder to digest compared to whey protein [1]
- Breast milk: whey:casein = 60:40 in mature milk (90:10 in colostrum) [2]
- Cow's milk: whey:casein = 20:80 → much harder for infants to digest
- Breast milk fat has built-in lipase within the fat globule membrane → self-digestion [1]
- Pancreatic amylase and lipase don't reach adult levels until ~6 months → infant depends on breast milk enzymes [3]
In developing countries, the commonest cause of infant death is gastroenteritis [1]
- Formula feeding requires clean water, sterilised bottles, correct dilution – all of which may be unavailable
- Breast milk is sterile at delivery and contains anti-infective factors (sIgA, lactoferrin, lysozyme)
- Infection increases energy requirement → recurrent infection → stunted growth (vicious cycle) [1]
Early exposure to foreign protein in the first few months increases risk of eczema and asthma [1]
- Atopy = inherited susceptibility + antigen exposure
- The immature intestinal tract is more permeable ("leaky gut"), allowing larger protein molecules through → sensitisation of the immune system
- Exclusive breastfeeding for 4–6 months reduces atopic disease risk in high-risk infants
Preterm infants have higher energy needs (120 kcal/kg/day), are more susceptible to LC-PUFA and cysteine deficiency [1]
| Condition | Special Need | Reason |
|---|---|---|
| Preterm | Higher energy, LC-PUFA, cysteine | Missed 3rd trimester nutrient accretion; immature enzyme systems |
| Galactosaemia | Lactose-free diet | Cannot metabolise galactose (lactose → glucose + galactose) → toxic galactose-1-phosphate accumulates |
| Infection | Higher energy | Fever and immune activation increase metabolic rate |
| Chronic lung disease | Higher energy | Increased work of breathing |
Galactosaemia is a Contraindication to Breastfeeding
Galactosaemia is one of the absolute contraindications to breastfeeding because breast milk contains lactose, which is hydrolysed to galactose. This infant needs a soy-based or galactose-free formula. Detected on newborn metabolic screening. [1]
2. Benefits of Breastfeeding
The lecture organises benefits into three categories: Infant, Mother, Socioeconomic [1].
Breast milk perfectly matches all five principles of infant feeding [1]
| Benefit | Mechanism |
|---|---|
| Nutritional value | Optimal macro/micronutrient composition, changes with infant age |
| Easily digested and absorbable | Whey-predominant protein, lipase-containing fat globules, MCT |
| Prevention of infection | sIgA coats gut mucosa, lactoferrin binds iron (depriving bacteria), lysozyme, white cells |
| Prevention of atopy | Avoids foreign protein exposure; sIgA prevents antigen uptake across gut |
| Preterm milk suits preterm needs | Breast milk from preterm mothers has higher protein, sodium, and immunoglobulin content |
Fertility control, bonding, uterine involution [1]
- Fertility control: via lactational amenorrhoea (prolactin suppresses GnRH → suppresses LH → no ovulation). Detailed criteria below.
- Bonding: oxytocin release during let-down promotes maternal-infant attachment
- Uterine involution: oxytocin causes uterine contraction → reduces postpartum haemorrhage and speeds return to pre-pregnancy uterine size
Additional maternal benefits from other sources [4]:
- Reduced risk of type 2 diabetes, breast cancer, ovarian cancer
- Promotes postpartum weight loss
Birth control, spacing pregnancies, decreased maternal death, prevention of infant infection/death, much less costly than bottle feeding [1]
- In resource-limited settings, these benefits are massive public health interventions
- Breastfeeding costs nothing vs formula (which is expensive and requires infrastructure)
Three key contraindications: current breast cancer, HIV-positive mother (with caveats), and infant galactosaemia [1]
| Contraindication | Rationale | Caveat |
|---|---|---|
| Current breast cancer | Active treatment (chemotherapy, radiotherapy) is toxic to infant via milk; also disruption of breast tissue | Previous breast cancer with completed treatment is NOT a contraindication |
| HIV-positive mother | HIV transmits through breast milk (12–20% of MTCT via breastfeeding) [5] | In developing countries where no safe alternative exists, breastfeeding should still be advised – the risk of death from malnutrition/diarrhoea outweighs HIV transmission risk |
| Galactosaemia | Lactose in breast milk → galactose → toxic accumulation | Detected on newborn screening |
HIV and Breastfeeding – The Nuance
In developed countries (like Hong Kong) with safe formula alternatives, HIV+ mothers should NOT breastfeed. In developing countries, WHO recommends breastfeeding WITH maternal ART because the mortality from formula-related infections exceeds the risk of HIV transmission through breast milk. This is a common exam discriminator. [1][5]
Additional contraindications from supporting sources [4]:
- Active untreated tuberculosis (until non-infectious)
- Mothers on chemotherapy or anti-metabolic drugs
- Substance abuse
- HSV lesions on breast (can feed from unaffected breast)
4. Promotion of Breastfeeding
Seven blocks identified in the lecture [1]:
- Home and work environment – lack of maternity leave, no facilities at work
- Attitude of society – stigma around public breastfeeding
- Lack of public facilities – no nursing rooms
- Lack of family support – pressure from family to use formula
- Lack of support from health professionals – doctors/nurses not trained in lactation support
- Promotion from formula milk companies – aggressive marketing
- "A lost tradition" – urbanisation and formula availability have eroded breastfeeding culture
This is the framework for the Baby-Friendly Hospital Initiative (BFHI) [1]
Critical Management Procedures (Steps 1–2):
| Step | Content |
|---|---|
| 1a | Comply fully with the International Code of Marketing of Breast-milk Substitutes |
| 1b | Have a written infant feeding policy communicated to staff and parents |
| 1c | Establish ongoing monitoring and data-management systems |
| 2 | Ensure staff have sufficient knowledge, competence, and skills to support breastfeeding |
Key Clinical Practices (Steps 3–10):
| Step | Content |
|---|---|
| 3 | Discuss importance and management of breastfeeding with pregnant women and families during pregnancy |
| 4 | Facilitate immediate and uninterrupted skin-to-skin contact and support mothers to initiate breastfeeding as soon as possible after birth |
| 5 | Support mothers to initiate and maintain breastfeeding and manage common difficulties |
| 6 | Do not provide breastfed newborns any food or fluids other than breast milk unless medically indicated |
| 7 | Enable rooming-in 24 hours a day |
| 8 | Support mothers to recognise and respond to infant feeding cues |
| 9 | Counsel mothers on use and risks of feeding bottles, teats, and pacifiers |
| 10 | Coordinate discharge so parents have timely access to ongoing support and care |
High-Yield: Steps 4, 6, 7
These three steps are the most commonly tested: early skin-to-skin contact (step 4), exclusive breastfeeding with no supplementation (step 6), and rooming-in (step 7). They directly support the physiology of lactation establishment.
5. Physiology of Lactation
This is the physiological core of the lecture. Understanding the hormone interplay explains clinical management of every breastfeeding problem.
Key structures: alveoli, adipose tissue, mammary/lactiferous ducts, areola, nipple [1]
- Alveoli: grape-like clusters of secretory epithelial cells surrounded by myoepithelial cells. This is where milk is actually produced.
- Myoepithelial cells: contractile cells that squeeze milk out of alveoli when stimulated by oxytocin
- Mammary ducts (lactiferous ducts): 15–20 ducts drain milk from lobules to the nipple [6]
- Areola: contains Montgomery's tubercles (sebaceous glands that lubricate nipple during lactation) [6]
- Nipple: contains the orifices of the lactiferous ducts
- Adipose tissue: determines breast size (but NOT milk-producing capacity)
- Cooper's ligaments: fibrous septae between lobules; not directly relevant to lactation but important in breast pathology [6]
Puberty: oestrogen → duct proliferation; progesterone → alveolar development [1]
Pregnancy: oestrogen + progesterone → further alveolar hypertrophy BUT inhibit milk production; prolactin (+ hPL) stimulate secretory activity [1]
| Stage | Hormonal Driver | Effect |
|---|---|---|
| Puberty | Oestrogen | Milk duct proliferation (branching of the ductal tree) |
| Progesterone | Alveolar development (lobule formation) | |
| Pregnancy | Oestrogen + Progesterone | Further alveolar hypertrophy (breast enlargement) BUT actively inhibit milk production |
| Prolactin + hPL | Stimulate secretory activity (the cells are primed to make milk but are held back by the high E/P) |
Key concept: During pregnancy, prolactin levels are rising enormously, but actual milk secretion is suppressed by the high oestrogen and progesterone from the placenta. This is why delivery (and loss of the placenta) is the trigger for lactation.
5.3 Lactation: Three Phases
After delivery, oestrogen and progesterone levels rapidly decline, removing inhibition on milk production [1]
- The placenta is the source of E and P during pregnancy. Its delivery causes a precipitous drop in these hormones within hours.
- Prolactin, which has been building up during pregnancy, is now "unbraked" and can drive milk synthesis.
- This is why colostrum (the initial thick, yellow milk rich in immunoglobulins) appears within 1–3 days postpartum before mature milk "comes in" around days 3–5.
Sheehan Syndrome – When Initiation Fails
If the anterior pituitary is infarcted due to severe postpartum haemorrhage (Sheehan syndrome), prolactin production is lost → inability to lactate + failure to resume menstruation (loss of gonadotropins). This was tested in 2023 MCQ Q38. The answer is "AVP deficiency" (posterior pituitary may also be affected). Remember that Sheehan syndrome causes panhypopituitarism. [8]
Suckling drives both milk production (prolactin) and milk ejection (oxytocin) [1]
Two reflexes maintain lactation:
Milk Production Reflex (Prolactin Reflex):
Suckling → afferent nerve → hypothalamus → inhibits dopamine release → removes dopamine inhibition on prolactin → anterior pituitary releases prolactin → milk production [1]
- Dopamine is the prolactin-inhibiting factor (PIF). Under normal (non-lactating) conditions, dopamine tonically inhibits prolactin release.
- Suckling sends afferent signals via intercostal nerves (T4-T6) to the hypothalamus
- The hypothalamus responds by reducing dopamine secretion into the portal system
- With less dopamine inhibition, lactotroph cells in the anterior pituitary release prolactin
- Prolactin acts on alveolar epithelial cells to synthesise milk
This explains why:
- Dopamine agonists (bromocriptine, cabergoline) suppress lactation (they mimic dopamine's inhibitory effect)
- Dopamine antagonists (metoclopramide, domperidone) can increase milk production (used off-label as galactogogues)
- Frequent suckling = more prolactin = more milk (demand drives supply)
Milk Ejection (Let-Down) Reflex (Oxytocin Reflex):
Suckling → afferent nerve → hypothalamus → production and transport of oxytocin to posterior pituitary → oxytocin released → contraction of myoepithelial cells → milk ejection [1]
- Oxytocin is synthesised in the paraventricular and supraoptic nuclei of the hypothalamus
- Transported down axons to the posterior pituitary (neurohypophysis) for storage and release
- Acts on myoepithelial cells surrounding alveoli → squeezing milk into the ducts and towards the nipple
- Also causes uterine contraction (which is why breastfeeding mothers feel "afterpains" – and why breastfeeding promotes uterine involution)
Important clinical point: The let-down reflex can be conditioned – hearing the baby cry, thinking about the baby, or even the sound of a breast pump can trigger it. Conversely, anxiety and stress inhibit the let-down reflex (cortisol/catecholamines may suppress oxytocin release), which is why a calm, supportive environment is critical for successful breastfeeding.
Two mechanisms cause milk production to cease: [1]
- Pressure built up by milk accumulating in the alveoli (back-pressure inhibits secretion)
- Diminished stimulation of glandular epithelium by prolactin (less suckling → less prolactin)
- As feeds become less frequent, prolactin pulses decrease
- Milk accumulates → increased intraluminal pressure → Feedback Inhibitor of Lactation (FIL) – a protein in breast milk that locally inhibits further milk synthesis when milk is not removed
- Eventually, alveolar cells involute and the breast returns towards its pre-pregnancy state
Elevated prolactin + reduced GnRH → reduced LH → suppressed ovulation [1]
LAM is effective as contraception ONLY if all THREE criteria are met: [1]
- Amenorrhoea
- Fully or nearly fully breastfeeding (no interval > 4–6 hours between feeds)
- < 6 months postpartum
But 10% of women DO have ovulatory cycles while breastfeeding [1]
Why does this work?
- High prolactin from frequent suckling suppresses pulsatile GnRH release from the hypothalamus
- Without GnRH pulses, the anterior pituitary cannot produce adequate LH surges
- Without the LH surge, no ovulation occurs
Why does it fail?
- If breastfeeding frequency decreases (e.g., supplementation with formula, longer sleep intervals), prolactin drops and GnRH pulsatility recovers
- After 6 months, even with frequent feeding, the hypothalamic sensitivity to prolactin's suppressive effect wanes
- This is why LAM is NOT a reliable long-term contraceptive method
Exam Trap: LAM Criteria
Students frequently forget one of the three criteria or forget that 10% of women ovulate despite breastfeeding. If even ONE criterion is not met, additional contraception is needed. [1]
6. How to Establish Lactation
Early and frequent suckling, correct positioning, avoid artificial teats, avoid fatigue and anxiety [1]
- Early suckling: ideally within 1 hour of birth (skin-to-skin contact per WHO Step 4)
- Frequent suckling: drives prolactin reflex → more milk production. Typically 8–12 feeds/day in the first weeks
- Avoid artificial teats: "nipple confusion" – the sucking mechanism for a bottle is different from the breast; early bottle exposure may interfere with breastfeeding
- Avoid fatigue and anxiety: stress inhibits let-down reflex; mother needs rest and support
Key points of position: [1]
- Support baby's whole body with head and body in a line
- Baby close to mother
- Support the whole body
- Nose to nipple
Key points of attachment: [1]
- Chin leads (baby approaches breast chin-first)
- Wide open mouth
- Bottom lip touches breast well away from base of nipple
- Nipple towards rear of roof of mouth
- Cheeks are round during suckling (not dimpled/sucked in)
| Proper Suckling | Improper Suckling |
|---|---|
| Whole areola is in baby's mouth | Only the nipple is inside the mouth |
| Tongue presses on the milk ducts (compressing them to extract milk) | Gums chew on the nipple |
| Gums are NOT chewing the nipple | Causes sore/cracked nipples, ineffective milk transfer |
Why does this matter so much? Improper latch is the single most common cause of sore nipples and insufficient milk transfer. If the baby only sucks on the nipple (rather than the areola), the tongue cannot compress the ducts, milk flow is poor, the baby gets frustrated, and the nipple gets traumatised. This sets up a cascade: sore nipples → less feeding → engorgement → blocked ducts → mastitis.
7. Maternal Breast Problems During Lactation
This is a clinical progression – understand it as a spectrum from mild to severe:
Sore nipples → Breast engorgement → Blocked ducts → Mastitis → Breast abscess [1]
| Feature | Engorgement | Blocked Duct | Mastitis | Breast Abscess |
|---|---|---|---|---|
| Onset | Gradual, D3–5 | Gradual, after feeds established | ~2–3 weeks postpartum | First 6 weeks |
| Laterality | Bilateral | Unilateral | Unilateral | Unilateral |
| Distribution | Generalised | Localised | Localised (wedge-shaped area) | Localised, fluctuant |
| Systemic symptoms | Mild | None/mild | Fever, malaise | Fever, toxicity |
| Cause | Milk "coming in" before adequate removal | Poor drainage of one segment | Non-effective milk removal → milk stasis + infection | Complication of mastitis |
| Organism | N/A | N/A | Staphylococcus aureus | S. aureus |
| Key management | Frequent feeding, express before feed, analgesia | Continue feeding, warm compress, massage, change position | Effective milk removal, continue BF, warm compress, antibiotics if indicated | Drainage (aspiration or I&D) + antibiotics |
Gradual onset, usually around D3–5, bilateral and generalised [1]
- Occurs when milk "comes in" (transition from colostrum to mature milk)
- The breasts become distended, hard, warm, and painful
- Management: [1]
- Proper positioning and latching on
- Frequent feeding (demand-driven, not scheduled)
- Express milk before feeding (softens the areola, making latch easier)
- Analgesic (paracetamol or ibuprofen)
This was tested in 2025 MCQ Q9: A 27-year-old woman with fullness and tenderness in left breast after 1 week of exclusive breastfeeding → correct answer: "Try to express the milk by breast pump" (option D). Cabergoline (option B) would suppress lactation. Formula (option A) worsens the problem by reducing suckling. Antibiotics (option C) are not indicated for simple engorgement. [9]
Gradual onset, after initiation of feeding, unilateral, more localised. May lead to mastitis. [1]
- A segment of the breast has a tender lump where milk is not draining properly
- No systemic symptoms (no fever)
- Management: [1]
- Continue feeding (stopping would worsen the blockage)
- Warm compress
- Massage (towards the nipple, during feeding)
- Change feeding position (baby's chin should point towards the blocked area – suction is strongest at the chin)
- Effective removal of milk
Usually occurs around 2–3 weeks after delivery. Non-effective removal of milk → milk stasis and infection. [1]
Infective mastitis: Staphylococcus aureus [1]
Pathophysiology:
- Milk stasis (from poor drainage, engorgement, or blocked ducts)
- Bacteria (usually S. aureus from baby's oropharynx or mother's skin) enter via cracked nipple or retrograde through ducts
- Stagnant milk is an excellent culture medium
- Inflammatory response → red, hot, wedge-shaped area of breast + fever + malaise
Management – Conservative first: [1]
- Effective milk removal – continue breastfeeding (the milk is safe for the baby; the infection is in the breast tissue, not the milk)
- Express milk if baby cannot feed directly
- Moist heat / warm compress
- Massage
- Adequate fluid intake
- Analgesics
When to add antibiotics: [1]
Antibiotics indicated when:
- Severe symptoms
- Presence of nipple fissure (portal of entry for bacteria)
- Persistent symptoms despite improved milk removal
- Positive bacterial culture
Antibiotic choices: [1]
- Erythromycin
- Dicloxacillin
- Amoxicillin (note: amoxicillin-clavulanate may be preferred for broader coverage)
- Cephalexin
All of these are generally safe during breastfeeding.
Occurs more commonly in first 6 weeks. Complication of mastitis. [1]
- An abscess is a walled-off collection of pus
- Suspect when mastitis does not respond to antibiotics within 48–72 hours [6]
- Diagnosis: clinical ± ultrasound to confirm collection
Management: [1]
- Drainage:
- Aspiration (preferred initially – less scarring, can be repeated)
- Incision and drainage (if aspiration fails, or skin is ischaemic/necrotic) [6]
- Antibiotics
- Can still breastfeed from the contralateral breast; may feed from the affected side if the incision is away from the areola
8. Medication During Breastfeeding
Drug → Maternal gut/liver (oral bioavailability varies) → Maternal plasma (concentration varies) → Milk (non-protein-bound drugs can pass) → Infant gut (oral bioavailability varies) → Infant plasma (usually very low level) [1]
Each step acts as a "filter" that reduces the amount of drug reaching the infant:
- Maternal oral bioavailability: only a fraction of the oral dose reaches maternal plasma
- Protein binding: only unbound (free) drug can cross into milk
- Milk-plasma ratio: determines how much drug concentrates in milk relative to plasma
- Infant oral bioavailability: the drug must survive the infant's GI tract to be absorbed
- Infant metabolism: the infant's liver and kidneys process whatever is absorbed
| Property | Why |
|---|---|
| Highest plasma protein binding | Less free drug available to cross into milk |
| Lowest plasma concentration | Less drug available at the milk interface |
| Lowest bioavailability | Even if drug enters milk, less is absorbed by infant's gut |
| Lowest milk-plasma ratio | Drug doesn't concentrate in milk |
| Shortest half-life | Drug is cleared quickly; can time feeds to avoid peak levels |
| Least toxicity | If some drug does reach the infant, it won't cause harm |
Safe vs Unsafe in Pregnancy ≠ Lactation
A common exam trap: students assume that drugs safe in pregnancy are also safe during breastfeeding. This is NOT always true. For example, some drugs that don't cross the placenta well may still cross into breast milk. Always check specifically for lactation safety. [1]
LactMed (NIH database – freely accessible), UKDILAS (UK Drugs in Lactation Advisory Service), Hale's Medications & Mothers' Milk [1]
While not the primary focus of this Part I lecture, understanding the distinction between breastfeeding jaundice and breast milk jaundice is essential and frequently examined alongside lactation physiology.
| Feature | Breastfeeding Jaundice | Breast Milk Jaundice |
|---|---|---|
| Timing | 1st week (early) | After 1–2 weeks (late; persists to 3–12 weeks) |
| Mechanism | Inadequate milk intake → poor stooling → ↑enterohepatic circulation → ↑unconjugated bilirubin | β-glucuronidase in breast milk → deconjugates bilirubin in gut → ↑reabsorption |
| Management | Improve breastfeeding technique and frequency | Continue breastfeeding; benign, self-limiting |
| Key point | This is a feeding failure problem, not a breast milk problem | This is a breast milk composition effect |
| Component | Colostrum (Day 1–3) | Mature Milk (Day 14+) |
|---|---|---|
| Protein | Higher (especially sIgA) | Lower but adequate |
| Whey:Casein | 90:10 | 60:40 |
| Fat | Lower | Higher (provides most energy) |
| Lactose | Lower | Higher |
| sIgA | Very high | Lower but present |
| Calories | Lower | ~67 kcal/100 mL |
| Colour | Yellow (carotenoids) | Bluish-white |
Likely Exam Questions
-
A 28-year-old primiparous woman is exclusively breastfeeding her 4-week-old baby. She is amenorrhoeic. Which criterion, if absent, would make the lactational amenorrhoea method (LAM) unreliable as contraception?
- A. Baby is < 6 months old
- B. Mother is amenorrhoeic
- C. Breastfeeding intervals are 8 hours overnight ✓
- D. Mother is exclusively breastfeeding
Markscheme: LAM requires feeds no more than 4–6 hours apart. An 8-hour overnight gap breaks this criterion. [1]
-
Which hormone's decline after delivery is the primary trigger for initiation of lactation?
- Answer: Oestrogen and progesterone (from placental loss). Their decline removes the inhibition on milk production that was maintained despite rising prolactin during pregnancy. [1]
-
A breastfeeding mother develops a tender, red, wedge-shaped area on her right breast with fever at 3 weeks postpartum. What is the most likely causative organism?
- Answer: Staphylococcus aureus. [1]
-
List the five principles of infant feeding. (5 marks)
- Adequate nutrition for homeostasis and growth
- Food easily digested and absorbed
- Clean source, prevention of infection
- Avoid early foreign protein exposure (atopy prevention)
- Special requirements for preterm/metabolic disease [1]
-
Describe the milk production reflex pathway. (3 marks)
- Suckling → afferent nerve → hypothalamus → inhibits dopamine release → removes inhibition on anterior pituitary lactotrophs → prolactin release → milk production [1]
-
A breastfeeding mother presents with bilateral breast fullness, hardness, and pain on day 4 postpartum. Name the condition, and list 4 management steps. (5 marks)
- Breast engorgement
- Proper positioning and latching, frequent feeding, express milk before feeding, analgesics [1]
High Yield Summary
Five Principles of Infant Feeding: Adequate nutrition (110 kcal/kg/day), easily digested food, clean source / infection prevention, avoid early foreign protein (atopy), special needs for preterm/metabolic disease.
Benefits of breastfeeding: Infant (nutrition, digestion, infection prevention, atopy prevention, preterm-matched); Mother (fertility control, bonding, uterine involution); Socioeconomic (cost, birth spacing, reduced mortality).
Contraindications: Current breast cancer, HIV (unless no safe alternative), galactosaemia.
Physiology: Pregnancy = E+P inhibit milk production despite rising prolactin. Delivery = E+P fall → lactation initiates. Maintenance = suckling drives prolactin (production) and oxytocin (ejection). Weaning = back-pressure + less prolactin.
Lactational Amenorrhoea Method (LAM): 3 criteria: amenorrhoea + fully/nearly fully BF (no > 4–6h gap) + < 6 months PP. 10% still ovulate.
Breast problems spectrum: Engorgement (bilateral, D3–5) → Blocked duct (unilateral, localised) → Mastitis (2–3 wks, S. aureus, antibiotics if severe) → Abscess (drainage needed).
Drugs in lactation: Choose high protein binding, low bioavailability, short half-life, least toxic. Infant gets ~1% of maternal dose. Anti-cancer/anti-metabolic drugs are contraindicated. Safe in pregnancy ≠ safe in lactation.
Active Recall - Lecture Notes
[1] Lecture slides: CFB (OGPAE02-1) Physiology of Lactation, Breast Feeding and Infant Feeding (Part I).pdf [2] Senior notes: Adrian Lui Pediatrics Notes.pdf (Section 3.3.1 Infant Feeding) [3] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (Section on pathophysiology of nutrition uptake) [4] Paediatrics notes: Maksim Paediatric Notes.pdf (Section 1.7 Nutrition) [5] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (Section on mother-to-child transmission of HIV) [6] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (Breast Diseases section) [7] Senior notes: Ryan Ho Haemtology.pdf (Iron deficiency in breastfeeding children) [8] Past papers: 2023 Fourth Summative MCQ.pdf (Question 38) [9] Past papers: 2025 Fourth Summative MCQ.pdf (Question 9) [10] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (Breastmilk jaundice and breastfeeding jaundice) [11] Paediatrics lecture slides: Block C - A jaundiced child.pdf (enterohepatic circulation in breastfeeding)
CFB OGPAE01-2 Perinatal Medicine, Antenatal Care And Pre-pregnant Counselling (part II)
Continuation of perinatal medicine education covering advanced aspects of antenatal care, including screening strategies, management of high-risk pregnancies, and pre-pregnancy counselling to optimize maternal and fetal outcomes.
CFB OGPAE02-2 Physiology Of Lactation, Breast Feeding And Infant Feeding (part II)
Lactation physiology involves the hormonal regulation of milk production and ejection, alongside the principles of breastfeeding techniques and appropriate infant feeding practices to ensure optimal neonatal nutrition and growth.