Physiology of Lactation
Adapted from the course onAdapted from the course onBreastfeeding : Advocacy & PracticeBreastfeeding : Advocacy & PracticeMalaysia 2007Malaysia 2007
Stages of LactationStages of Lactation
MammogenesisMammogenesis
LactogenesisLactogenesis
Lactogenesis ILactogenesis I
Lactogenesis IILactogenesis II
GalactopoiesisGalactopoiesis
Lactogenesis IIILactogenesis III InvolutionInvolution
Mammogenesis -Mammogenesis -
““priming”- growth and priming”- growth and development of ducts & alveoli in development of ducts & alveoli in the first 12 weeks of pregnancythe first 12 weeks of pregnancy
The breast is prepared for The breast is prepared for lactation by 16 weeks lactation by 16 weeks
LactogenesisLactogenesis
Lactogenesis ILactogenesis I
– starts at 28 weeks pregnancystarts at 28 weeks pregnancy
– Substrate for milk production Substrate for milk production collect in breast tissuecollect in breast tissue
– Early secretion – production of Early secretion – production of colostrum startscolostrum starts
Lactogenesis IILactogenesis II
–starts at 3-4 days after deliverystarts at 3-4 days after delivery
of placenta, progesterone of placenta, progesterone & & estrogen = stimulates milk estrogen = stimulates milk synthesissynthesis
–Blood flows to breast increasesBlood flows to breast increases
–Production of transition milk Production of transition milk starts milk “comes in”starts milk “comes in”
Retained placenta – inhibitsRetained placenta – inhibits
Initiation of milk productionInitiation of milk production
depends on changed hormone depends on changed hormone
levels -----NOT on early levels -----NOT on early
sucklingsuckling
Continuation of milk Continuation of milk
productionproduction after 3-4 days DOES after 3-4 days DOES
depend on infant sucklingdepend on infant suckling
Lactogenesis IILactogenesis II
Lactogenesis III or GalactopoiesisLactogenesis III or Galactopoiesis
– From 10 days after deliveryFrom 10 days after delivery
– Mature milk is producedMature milk is produced
– Production sustained if baby Production sustained if baby
continues to breastfeedcontinues to breastfeed
– Volume depends on the amount Volume depends on the amount
baby removesbaby removes
Single baby – 750 mls / 24 hrsSingle baby – 750 mls / 24 hrs
for Twins - 1500 mls / 24 hrsfor Twins - 1500 mls / 24 hrs
As baby grows and weight As baby grows and weight increases, milk need per kilo of increases, milk need per kilo of body weight decreasesbody weight decreases
So total milk needs remains So total milk needs remains about the same from 6 weeks to 6 about the same from 6 weeks to 6 months despite growthmonths despite growth
Lactogenesis III or GalactopoiesisLactogenesis III or Galactopoiesis
InvolutionInvolution
When other feeds / foods satisfy When other feeds / foods satisfy appetite baby suckle less appetite baby suckle less production decreases production decreases milk cells die Milk in the milk cells die Milk in the breast is reabsorbed.breast is reabsorbed.
Last milk produced is more like Last milk produced is more like colostrum with many protective colostrum with many protective bodiesbodies
Role of HormonesRole of Hormones(primes mammary glands)(primes mammary glands)
Estrogen – growth of ductsEstrogen – growth of ducts
Progesterone – growth of alveoliProgesterone – growth of alveoli
Placental Lactogen - growth of milk Placental Lactogen - growth of milk
producing cells in the alveoliproducing cells in the alveoli
Prolactin – helps growth of ducts Prolactin – helps growth of ducts
and alveoli /stimulates alveoli cells and alveoli /stimulates alveoli cells
to produce milkto produce milk
ProlactinProlactin in bloodin blood
Baby Baby sucklingsuckling
Sensory impulses Sensory impulses from nipplesfrom nipples
• More prolactin More prolactin secreted at nightsecreted at night
• Suppresses Suppresses ovulationovulation
:
Secreted Secreted duringduring and a and afterfterfeed to produce feed to produce nextnext feed feed
Prolactin ReflexProlactin Reflex
Prolactin LevelsProlactin Levels
Prolactin blood levels:Prolactin blood levels: ng /ml ng /ml
Menstruating woman:Menstruating woman: 8 – 14 8 – 14End of pregnancy:End of pregnancy: 200 – 500 200 – 500
Baseline during lactation:Baseline during lactation:- From delivery to 10 days: - From delivery to 10 days: 200 200- 10 – 90 days:- 10 – 90 days: 60 – 100 60 – 100- 90 – 180 days:- 90 – 180 days: 50 50- 180 days – 1 year:- 180 days – 1 year: 30 – 4030 – 40
Prolactin level
Each breastfeedingEach breastfeeding causes a causes a rise in Prolactinrise in Prolactin
x 5 baseline in early x 5 baseline in early lactation, lactation,
x 2 in late lactation.x 2 in late lactation.
Prolactin rise is maximum Prolactin rise is maximum 30 30 minutes minutes after feedafter feed..
Oxytocin reflexOxytocin reflex
Makes uterus Makes uterus contractcontract
Sensory impulsesSensory impulses
from nipplesfrom nipplesOxytocinOxytocin
in bloodin blood
BabyBaby
sucklingsuckling
Works Works beforebefore or or duringduring
feed to make milk flowfeed to make milk flow
• WorryWorry
• StressStress
• PainPain
• DoubtDoubt
hinder hinder reflexreflexhelp help reflexreflex
• Thinks lovingly of babyThinks lovingly of baby
• Sounds / sight of babySounds / sight of baby
•Touching babyTouching baby
•ConfidenceConfidence
Helping and hindering of Helping and hindering of
oxytocin reflexoxytocin reflex
NEUROENDOCRINE PATHWAYS NEUROENDOCRINE PATHWAYS INITIATED BY SUCKLINGINITIATED BY SUCKLING
Milk productionMilk production
FFirst 4 – 6 weeks after delivery irst 4 – 6 weeks after delivery is very variableis very variable
At 5 days = 200 – 900 ml / 24 At 5 days = 200 – 900 ml / 24 hourshours
At 4 – 6 weeks = 400 – 1100 At 4 – 6 weeks = 400 – 1100 ml/24 hoursml/24 hours
Milk production
Milk production starts:Milk production starts: low and increases (up-regulation) – low and increases (up-regulation) –
in most women in most women high and decreases (down-high and decreases (down-
regulation) - in some womenregulation) - in some women until it adjusts to the needs of the until it adjusts to the needs of the
baby.baby.
Milk production Milk production at this at this timetime is not related to is not related to size of babysize of baby
Milk productionMilk production
By 4 – 6 weeks, production adjusts to By 4 – 6 weeks, production adjusts to baby’s needsbaby’s needs
Milk production is now related to size of babyMilk production is now related to size of baby
- regulated by baby’s demand regulated by baby’s demand - baby’s fat or calorie intake controls baby’s fat or calorie intake controls
appetite and hence demandappetite and hence demand
If supplements are given appetite is If supplements are given appetite is satisfied demand is less satisfied demand is less
Hartmann et al (1993) – a study Hartmann et al (1993) – a study found that babies removed an found that babies removed an average of only average of only 76% of the 76% of the available milkavailable milk from their mothers’ from their mothers’ breast in a 24-hr period.breast in a 24-hr period.
Wilde 1995 – a special protein in Wilde 1995 – a special protein in human milk called human milk called feedback feedback inhibitor of lactation (FIL)inhibitor of lactation (FIL) regulates milk production.regulates milk production.
It is chemical inhibitorIt is chemical inhibitor
Is an autocrine or local regulator Is an autocrine or local regulator of breastmilk synthesisof breastmilk synthesis
Is a protein made in the breast Is a protein made in the breast itselfitself
If not removed it collects in the If not removed it collects in the alveoli and blocks milk secretion alveoli and blocks milk secretion in the mammary cellsin the mammary cells
Feedback Inhibitor of Lactation (FIL)Feedback Inhibitor of Lactation (FIL)
Volume, frequency, fat contentStudy by Kent, Ramsay et al (2006)
Result:Result:
Left and right breast volume differLeft and right breast volume differ
Fat inversely related to 24hr volume from Fat inversely related to 24hr volume from that breastthat breast
No relationship between # of BFs and 24 No relationship between # of BFs and 24 hour milk productionhour milk production
Night breastfeeding has important Night breastfeeding has important contribution to volumecontribution to volume
Encourage on demandEncourage on demand
feedingfeeding
Factors that impair milk productionFactors that impair milk production
1. Inefficient milk removal due to:Inefficient milk removal due to:
- Poor attachmentPoor attachment
- Insufficiently sucklingInsufficiently suckling
- Addition of supplementsAddition of supplements
- Infrequent feedsInfrequent feeds
- Short feedsShort feeds
- No night feedsNo night feeds
2.2. Impaired ejection – anxiety, pain Impaired ejection – anxiety, pain
(temporary)(temporary)
3. Retained placenta products 3. Retained placenta products
(hormones inhibit prolactin)(hormones inhibit prolactin)
4. Oestrogens (e.g., in combined 4. Oestrogens (e.g., in combined
hormonal contraceptives)hormonal contraceptives)
5. Pregnancy5. Pregnancy
Factors that impair milk productionFactors that impair milk production
6. 6. Lack of prolactinLack of prolactin
- Primary deficiency - (very rare)- Primary deficiency - (very rare) - Smoking (nicotine may lead to lower - Smoking (nicotine may lead to lower
prolactin levels)prolactin levels)
7. Physical abnormality (breast 7. Physical abnormality (breast agenesis) agenesis)
8. Severe malnutrition8. Severe malnutrition
Factors that impair milk productionFactors that impair milk production