Physiology Of Lactation

Physiology of Lactation

Adapted from the course on Breastfeeding : Advocacy & Practice Malaysia 2007

Stages of Lactation Mammogenesis Lactogenesis Lactogenesis I Lactogenesis II Galactopoiesis

Lactogenesis III Involution

Mammogenesis “priming”- growth and development of ducts & alveoli in the first 12 weeks of pregnancy The breast is prepared for lactation by 16 weeks

Lactogenesis Lactogenesis I starts at 28 weeks pregnancy Substrate for milk production collect in breast tissue Early secretion – production of colostrum starts

Lactogenesis II –starts at 3-4 days after delivery of placenta, progesterone & estrogen = stimulates milk synthesis –Blood flows to breast increases –Production of transition milk starts milk “comes in”

Lactogenesis II

Retained placenta – inhibits Initiation of milk production depends on changed hormone levels -----NOT on early suckling Continuation of milk production after 3-4 days DOES depend on infant suckling

Lactogenesis III or Galactopoiesis – From 10 days after delivery – Mature milk is produced – Production sustained if baby continues to breastfeed – Volume depends on the amount baby removes

Lactogenesis III or Galactopoiesis

Single baby – 750 mls / 24 hrs for Twins - 1500 mls / 24 hrs As baby grows and weight increases, milk need per kilo of body weight decreases So total milk needs remains about the same from 6 weeks to 6 months despite growth

Involution When other feeds / foods satisfy appetite baby suckle less production decreases milk cells die Milk in the breast is reabsorbed. Last milk produced is more like colostrum with many protective bodies

Role of Hormones (primes mammary glands) Estrogen – growth of ducts Progesterone – growth of alveoli Placental Lactogen - growth of milk producing cells in the alveoli Prolactin – helps growth of ducts and alveoli /stimulates alveoli cells to produce milk

: Prolactin Reflex

Sensory impulses from nipples

Prolactin in blood

Baby suckling

• More prolactin secreted at night • Suppresses ovulation

Secreted during and after feed to produce next feed

Prolactin Levels Prolactin blood levels:

ng /ml

Menstruating woman: End of pregnancy:

8 – 14 200 – 500

Baseline during lactation: - From delivery to 10 days: - 10 – 90 days: - 90 – 180 days: - 180 days – 1 year:

200 60 – 100 50 30 – 40

Prolactin level

Each breastfeeding causes a rise in Prolactin x 5 baseline in early lactation, x 2 in late lactation. Prolactin rise is maximum 30 minutes after feed.

Oxytocin reflex

Oxytocin in blood

Baby suckling

Sensory impulses from nipples

Makes uterus contract

Works before or during feed to make milk flow

help reflex

• Thinks lovingly of baby

• Sounds / sight of baby •Touching baby •Confidence

hinder reflex

• Worry • Stress • Pain • Doubt

Helping and hindering of oxytocin reflex

NEUROENDOCRINE PATHWAYS INITIATED BY SUCKLING

Milk production

First 4 – 6 weeks after delivery is very variable At 5 days = 200 – 900 ml / 24 hours At 4 – 6 weeks = 400 – 1100 ml/24 hours

Milk production

Milk production starts: low and increases (up-regulation) – in most women high and decreases (downregulation) - in some women until it adjusts to the needs of the baby.

Milk production at this time is not related to size of baby

Milk production

By 4 – 6 weeks, production adjusts to baby’s needs Milk production is now related to size of baby

- regulated by baby’s demand baby’s fat or calorie intake controls appetite and hence demand If supplements are given appetite is satisfied demand is less

Milk Production From Birth Baby’s Age

mls per day Range

Day 1 (0-24 hrs)

7 – 123

mls per feed

Average On Average 37

7

Day 2 (24-48 hrs) 44 – 335

84

14

Day 3 (48-72 hrs) 98 – 775

266

38

Day 4 (72-96 hrs)

385

58

Day 5 (96-120 hrs)

500

70

3 months 6 months

750 800

Hartmann et al (1993) – a study found that babies removed an average of only 76% of the available milk from their mothers’ breast in a 24-hr period. Wilde 1995 – a special protein in human milk called feedback inhibitor of lactation (FIL) regulates milk production.

Feedback Inhibitor of Lactation (FIL) It is chemical inhibitor Is an autocrine or local regulator of breastmilk synthesis Is a protein made in the breast itself If not removed it collects in the alveoli and blocks milk secretion in the mammary cells

Volume, frequency, fat content Study by Kent, Ramsay et al (2006)

Result: Left and right breast volume differ Fat inversely related to 24hr volume from that breast No relationship between # of BFs and 24 hour milk production Night breastfeeding has important contribution to volume Encourage on demand feeding

Factors that impair milk production 1. Inefficient milk removal due to: - Poor attachment - Insufficiently suckling - Addition of supplements - Infrequent feeds - Short feeds - No night feeds

Factors that impair milk production

2. Impaired ejection – anxiety, pain

(temporary) 3. Retained placenta products (hormones inhibit prolactin) 4. Oestrogens (e.g., in combined hormonal contraceptives) 5. Pregnancy

Factors that impair milk production

6. Lack of prolactin - Sheehans syndrome (after postpartum haemorrhage) - Primary deficiency - (very rare) - Smoking (nicotine may lead to lower prolactin levels) 7. Physical abnormality (breast agenesis) 8. Severe malnutrition

Factors that impair milk production

6. Lack of prolactin - Primary deficiency - (very rare) - Smoking (nicotine may lead to lower prolactin levels) 7. Physical abnormality (breast agenesis) 8. Severe malnutrition