4. Lactogenesis (Milk Production)

4.1 Phases of Lactogenesis

  1. Lactogenesis I (mid-pregnancy to early postpartum)
    • Milk components begin forming (colostrum)
    • Progesterone inhibits full secretion
  2. Lactogenesis II (day 2–3 postpartum)
    • Triggered by sharp fall in progesterone while prolactin remains high
    • Sudden increase in milk volume (“milk coming in”)
  3. Lactogenesis III (maintenance phase)
    • Controlled mainly by infant suckling and milk removal
    • Supply-demand regulated

4.2 Hormonal Control

  • Prolactin (anterior pituitary)
    • Stimulates milk synthesis
    • Levels rise with suckling stimulus
  • Oxytocin (posterior pituitary)
    • Causes alveolar contraction: milk ejection reflex
  • Estrogen and Progesterone
  • hPL, cortisol, insulin, thyroid hormones
  •  

4.3: Milk Ejection (Let-Down Reflex)

1 Oxytocin Reflex

  • Triggered by suckling or emotional cues (hearing baby cry)
  • Oxytocin causes contraction of myoepithelial cells around alveoli
  • Milk is propelled into ducts and nipple

4.4 Factors Influencing Let-Down

  • Enhancers: relaxation, warmth, confidence
  • Inhibitors: stress, pain, anxiety

4.5: Composition of Breast Milk

1 Colostrum

  • Produced first 2–5 days
  • Rich in:
    • Immunoglobulin A (IgA)
    • Lactoferrin
    • Leukocytes
    • Growth factors
    • Low volume but highly concentrated
  • Critical for immune protection and gut maturation

2 Transitional Milk (Day 5–14)

  • Higher calories and fat
  • Increasing lactose and volume

3 Mature Milk (After 2 Weeks)

  • Foremilk: watery, quenches thirst
  • Hindmilk: rich in fat, promotes growth

4 Nutritional Components

  • Carbohydrates: lactose
  • Proteins: casein, whey proteins
  • Fats: long-chain fatty acids
  • Vitamins and minerals
  • Enzymes (lipase, amylase)

4.5 Immunological Components

  • IgA
  • Lactoferrin
  • Lysozyme
  • Oligosaccharides (prebiotics)
  • Live immune cells

4.6: Lactational Amenorrhea

1 Mechanism

  • High prolactin suppresses GnRH
  • Low FSH and LH → inhibits ovulation
  • Natural but variable contraceptive effect

2 Lactational Amenorrhea Method (LAM)

  • Effective (>98%) if:
    • Baby is exclusively breastfed
    • Mother is within 6 months postpartum
    • Menstruation has not resumed

4.8: Clinical Aspects of Lactation

1 Common Issues

  • Engorgement
  • Blocked ducts
  • Mastitis
  • Nipple soreness or fissures
  • Poor latch
  • Inadequate milk supply

2 Management Principles

  • Frequent breastfeeding
  • Correct breastfeeding technique
  • Warm compresses
  • Antibiotics for mastitis if required
  • Lactation counseling

 4.8: Infant Benefits of Breastfeeding

1 Nutritional Benefits

  • Ideal composition for growth
  • Easily digestible

2 Immunological Protection

  • Lower risk of infections
  • Gut protection and microbiome formation

3 Long-Term Outcomes

  • Improved cognitive development
  • Lower risk of obesity and metabolic disorders

4.9: Maternal Benefits of Breastfeeding

Short-Term Benefits

  • Faster uterine involution
  • Reduced postpartum bleeding
  • Natural contraception (LAM)

Long-Term Benefits

  • Reduced breast and ovarian cancer risk
  • Lower risk of type 2 diabetes
  • Emotional bonding

4.10: Summary

  • Lactation is hormonally regulated by prolactin (milk production) and oxytocin (milk ejection).
  • Breast milk composition changes from colostrum → transitional → mature milk.
  • Breastfeeding benefits both infant and mother.
  • Postpartum maternal physiology includes uterine involution, fluid shifts, and hormonal changes.
  • Lactational amenorrhea provides temporary natural contraception.
  • Clinical issues require prompt management and support.