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