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Lecture 17: Lactation Lecture 17: Lactation
•• Labor PainLabor Pain
•• Morphology of the BreastMorphology of the Breast
•• Hormonal Control of Hormonal Control of
LactationLactation
•• Milk CompositionMilk Composition
•• Benefits of LactationBenefits of Lactation
•• Energetics of LactationEnergetics of LactationBehavioral Biology of Women - 2006
Why is Labor Long in Humans?Why is Labor Long in Humans?
Stage 1 Stage 2
•• Dilation and Dilation and
Effacement of cervixEffacement of cervix
•• Mean = 14 hours in Mean = 14 hours in
first birthfirst birth
•• Expulsion of fetusExpulsion of fetus
•• Mean = 50 minutes in Mean = 50 minutes in
first birthsfirst births
•• 20 minutes in later 20 minutes in later
birthsbirths
Why is Labor Long in Humans?Why is Labor Long in Humans?
0 100 200 300 400 500 600 700 800
Baboon
Gorilla
Chimpanzees
Humans
Minutes
First Stage: Dilation and Effacement of Cervix
Second Stage: Expulsion of Fetus
Why is Labor Painful in Humans?Why is Labor Painful in Humans?
The size of fetal head going through pelvis?
Why is Labor Painful in Humans?Why is Labor Painful in Humans?The need for the cervix to dilate to 10 cm to
accommodate the large fetal head?
How is Human Birth Different?How is Human Birth Different?
Although rotation Although rotation
through the pelvis through the pelvis
contributes to the contributes to the
duration and degree of duration and degree of
difficulty during labor difficulty during labor ……
Difficult labor in humans is Difficult labor in humans is
primarily due to the the primarily due to the the
degree of cervical dilation degree of cervical dilation
necessary to accommodate necessary to accommodate
the size of the human fetal the size of the human fetal
head (3x greater than in head (3x greater than in
apes).apes).
22
•• Humans spend significantly more time in Humans spend significantly more time in
the later stages of dilation when pain is the later stages of dilation when pain is
greatest.greatest.
Why is Labor Painful in Humans?Why is Labor Painful in Humans?
•• Apes probably experience relatively little Apes probably experience relatively little
pain during labor because they have pain during labor because they have
relatively little dilationrelatively little dilation
Labor PainLabor Pain
•• Why does relaxation Why does relaxation
help?help?
•• Autonomic nervous Autonomic nervous
systemsystem
>> Parasympathetic Parasympathetic
(relaxation)(relaxation)
>> Sympathetic (fight or Sympathetic (fight or
flight response)flight response)
Assisted Birth in HumansAssisted Birth in Humans
•• Birth is routinely performed with assistance in Birth is routinely performed with assistance in
humans.humans.
•• Emotional support to the motherEmotional support to the mother
•• Mechanical assistanceMechanical assistance
Birth Support (Birth Support (doula doula effect)effect)
Sosa, et al. (1980)Sosa, et al. (1980)
0
10
20
30
40
50
60
70
No
Problems
Intervention
Cesarean
Oxytocin
Length of
Labor
Suported Unsupported
Assisted Birth in HumansAssisted Birth in Humans
•• Birth is routinely performed with Birth is routinely performed with
assistance in humans.assistance in humans.
•• Emotional support to the motherEmotional support to the mother
•• Mechanical assistanceMechanical assistance
>> May be particularly important May be particularly important
for breech births (2 for breech births (2 -- 4% of 4% of
births)births)
(Gregory et al. 1999)
33
Morphology of the BreastMorphology of the Breast
44
Breast DevelopmentBreast Development Breast Changes during PregnancyBreast Changes during Pregnancy
((mammogenesismammogenesis))•• Estrogen causes growth of ducts and Estrogen causes growth of ducts and
proliferation of alveoliproliferation of alveoli
Breast Changes during PregnancyBreast Changes during Pregnancy
•• Estrogen causes growth of ducts and Estrogen causes growth of ducts and
proliferation of alveoliproliferation of alveoli
•• Progesterone causes the alveolar milk Progesterone causes the alveolar milk
glands to matureglands to mature
Breast Changes during PregnancyBreast Changes during Pregnancy
•• ProlactinProlactin,, cortisol cortisol and growth hormone turn and growth hormone turn
breast cells into:breast cells into:
>> Secretory cells that make milkSecretory cells that make milk
>> Muscle cells that will squeeze milk down Muscle cells that will squeeze milk down
through ductsthrough ducts
Morphology of AlveolusMorphology of Alveolus
•• Site of milk synthesisSite of milk synthesis
Morphology of AlveolusMorphology of Alveolus
•• Site of milk synthesisSite of milk synthesis
•• Contained with a capsule of basement membrane which Contained with a capsule of basement membrane which contains contractile contains contractile myoepithelial myoepithelial cells.cells.
55
Stages of Breast Milk ProductionStages of Breast Milk Production
•• MammogenesisMammogenesis: establishment of glandular : establishment of glandular
morphology capable of producing large morphology capable of producing large
quantities of milkquantities of milk
Mammogenesis(complete at 4 mths)
Stages of Breast Milk ProductionStages of Breast Milk Production
•• LactogenesisLactogenesis: establishment of actively : establishment of actively secreting mammary glandsecreting mammary gland
Lactogenesis(Begins at Parturition)
Stages of Breast Milk Production Stages of Breast Milk Production
Hormones of LactationHormones of Lactation
•• GalactopoiesisGalactopoiesis: maintenance of milk secretion: maintenance of milk secretion
Galactopoiesis
Prolactin & Milk ProductionProlactin & Milk ProductionNeuroendocrine Neuroendocrine ReflexReflex
•• Nipple stimulationNipple stimulation
Prolactin & Prolactin &
Milk Milk
ProductionProduction
•• Nipple Nipple
stimulationstimulation
•• Hypothalamus Hypothalamus
stops producing stops producing
prolactinprolactin--
inhibiting factor inhibiting factor
(dopamine)(dopamine)
66
Prolactin & Prolactin &
Milk Milk
ProductionProduction
•• Hypothalamus Hypothalamus
stops producing stops producing
prolactinprolactin--inhibiting inhibiting
factor (dopamine)factor (dopamine)
•• Hypothalamus Hypothalamus
secretes VIP secretes VIP
((vasoactive vasoactive
intestinal intestinal
polypeptide)polypeptide)
Prolactin & Milk ProductionProlactin & Milk Production
•• Nipple stimulationNipple stimulation
•• Hypothalamus stops Hypothalamus stops
producing prolactinproducing prolactin--
inhibiting factor inhibiting factor
•• Hypothalamus secretes Hypothalamus secretes
VIP (VIP (vasoactive vasoactive
intestinal polypeptide)intestinal polypeptide)
•• In response,In response, Prolactin Prolactin is is
secreted from secreted from
lactotrophs lactotrophs in the in the
anterior pituitary anterior pituitary
Prolactin & Milk ProductionProlactin & Milk Production
•• Nipple stimulationNipple stimulation
•• Hypothalamus stops Hypothalamus stops
producing prolactinproducing prolactin--inhibiting inhibiting
factorfactor
•• Hypothalamus secretes VIP Hypothalamus secretes VIP
((vasoactive vasoactive intestinal intestinal
polypeptide)polypeptide)
•• In response,In response, ProlactinProlactin is is
secretedsecreted frm lactotrophsfrm lactotrophs in the in the
anterior pituitaryanterior pituitary
•• ProlactinProlactin stimulates mammary stimulates mammary
glands to produce milkglands to produce milk
Suckling and ProlactinSuckling and Prolactin
•• Increased suckling Increased suckling
produces increased milk produces increased milk
production.production.
•• Prolactin Prolactin approaches approaches
level of nonlevel of non--lactating lactating
women in 4women in 4--6 hours6 hours
Prolactin Prolactin in Nonin Non--Lactating Lactating
Women after stimulationWomen after stimulation
0
20
40
60
80
100
120
Baseline Immediate 15 minutes
Breast and Nipple
Breast Alone
Sternum
Forearm
Milk Letdown & OxytocinMilk Letdown & Oxytocin
•• Milk passes from alveoli, via Milk passes from alveoli, via
ducts, to the ducts, to the storage sinusesstorage sinuses
77
Milk Letdown & OxytocinMilk Letdown & Oxytocin
•• Milk passes from alveoli, via Milk passes from alveoli, via
ducts, to the ducts, to the storage sinusesstorage sinuses
•• Suckling stimulates mothers Suckling stimulates mothers
autonomic sensory nerves in autonomic sensory nerves in
the breastthe breast
Latching onLatching on
Latching onLatching on
•• Babies latch on to Babies latch on to
the areola,the areola, NOT the NOT the
nipplenipple
Milk Letdown & OxytocinMilk Letdown & Oxytocin
•• Suckling stimulates Suckling stimulates
mothers autonomic mothers autonomic
sensory nerves in the sensory nerves in the
breastbreast
•• Sends message to Sends message to
hypothalamushypothalamus
Milk Letdown & OxytocinMilk Letdown & Oxytocin
•• Sends message to Sends message to
hypothalamushypothalamus
•• Causes posterior Causes posterior
pituitary to produce pituitary to produce
oxytocinoxytocin
Milk Letdown & OxytocinMilk Letdown & Oxytocin
•• Causes posterior pituitary to Causes posterior pituitary to
produce oxytocinproduce oxytocin
•• Stimulates muscle cells in breast Stimulates muscle cells in breast
to contractto contract
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Milk Composition:Milk Composition: ColostrumColostrum
•• Produced in first few days Produced in first few days after birthafter birth
Milk Composition:Milk Composition: ColostrumColostrum
•• Produced in first few Produced in first few days after birthdays after birth
•• High in protein, low High in protein, low in fat and lactose in fat and lactose (milk sugar)(milk sugar)
Milk Composition:Milk Composition: ColostrumColostrum
•• Rich inRich inimmunoglobulins immunoglobulins (esp.(esp.IgA IgA andand IgGIgG))
•• Establish normal Establish normal bacterial flora of bacterial flora of infantinfant’’s digestive tracks digestive track
•• Provides epidermal Provides epidermal growth factors for final growth factors for final maturation of infant maturation of infant gut.gut.
Breast Milk ImmunityBreast Milk Immunity
•• Immunoglobulins Immunoglobulins in breast milk protects in breast milk protects
newborns against infectious diseasenewborns against infectious disease
99
Breast Milk ImmunityBreast Milk Immunity
•• Immunoglobulins Immunoglobulins in breast milk protects in breast milk protects
newborns against infectious diseasenewborns against infectious disease
•• PeyerPeyer’’s s patches in maternal gutpatches in maternal gut
Breast Milk ImmunityBreast Milk Immunity
•• Immunoglobulins Immunoglobulins in breast milk protects in breast milk protects
newborns against infectious diseasenewborns against infectious disease
•• PeyerPeyer’’s s patches in maternal gutpatches in maternal gut
•• Lymphocytes lodge in breast and produce Lymphocytes lodge in breast and produce
IgA IgA in breast milk which coats babyin breast milk which coats baby’’s s
intestines and prohibit foreign objects from intestines and prohibit foreign objects from
getting throughgetting through
Milk CompositionMilk Composition
•• ForemilkForemilk——milk milk
stored in ductsstored in ducts
•• Low fat, low protein, Low fat, low protein,
wateredwatered--downdown
•• 1/3 of total milk 1/3 of total milk
volume each nursingvolume each nursing
Milk CompositionMilk Composition
•• HindmilkHindmilk——milk milk stored in alveolar cells stored in alveolar cells
and released during let downand released during let down
•• High fat, high proteinHigh fat, high protein
Benefits of LactationBenefits of Lactation
•• Ingestion by Newborn Humans:Ingestion by Newborn Humans:
•• Lipids in human milk better absorbed than cows milkLipids in human milk better absorbed than cows milk
Benefits of LactationBenefits of Lactation
•• Ingestion by Ingestion by
Newborn Humans:Newborn Humans:
•• Lipids in human milk Lipids in human milk
better absorbed than better absorbed than
cows milkcows milk
•• Amino acids in cowAmino acids in cow’’s s
milk difficult for milk difficult for
newbornnewborn’’s liver to break s liver to break
down into important down into important
proteinsproteins
1010
Benefits of LactationBenefits of Lactation
•• Ingestion by Ingestion by Newborn Humans:Newborn Humans:
•• Lipids in human Lipids in human milk better milk better absorbed than absorbed than cows milkcows milk
•• Amino acids in cowAmino acids in cow’’s s milk difficult for milk difficult for newbornnewborn’’s liver to s liver to break down into break down into important proteinsimportant proteins
•• Form of iron not well Form of iron not well absorbedabsorbed
Benefits of LactationBenefits of Lactation
•• CompositionComposition
•• CowCow’’s milk low in s milk low in nucleotides: 25% nucleotides: 25% human, 6% cowhuman, 6% cow
Benefits of LactationBenefits of Lactation
•• CompositionComposition
•• Nucleotides Nucleotides ---- 25% 25% human, 6% cowhuman, 6% cow
•• Processing of cowProcessing of cow’’s milk s milk destroys destroys lactoferrin lactoferrin and and transferrin transferrin and other and other immunological cellsimmunological cells
Benefits of LactationBenefits of Lactation
•• CompositionComposition
•• Nucleotides Nucleotides ---- 25% 25%
human, 6% cowhuman, 6% cow
•• Processing of cowProcessing of cow’’s milk s milk
destroys destroys lactoferrin lactoferrin and and
transferrin transferrin and other and other
immunological cellsimmunological cells
•• CowCow’’s milk has different s milk has different
ratios of calcium, ratios of calcium,
phosphorous, magnesium, phosphorous, magnesium,
sodium and zincsodium and zinc
Benefits of LactationBenefits of Lactation
•• Infant Health:Infant Health:
•• Bottle fed babies Bottle fed babies have 2x the illness have 2x the illness rate and rate and
•• 3x hospital 3x hospital admission rate as admission rate as breast fed babiesbreast fed babies
Benefits of LactationBenefits of Lactation
•• Breast fed babies Breast fed babies have lower rates have lower rates of:of:
•• Ear infectionEar infection
•• PneumoniaPneumonia
•• BronchitisBronchitis
•• VomitingVomiting
•• DiarrheaDiarrhea
1111
Benefits of LactationBenefits of Lactation
•• Effects in adultsEffects in adults
•• Lower rates of diabetesLower rates of diabetes
•• Lower rates of asthmaLower rates of asthma
•• Lower cholesterol levelsLower cholesterol levels
•• Lower heart diseaseLower heart disease
•• Lower risk of breast Lower risk of breast
cancercancer
Lactation and Public PolicyLactation and Public Policy
How do we create a more How do we create a more ‘‘breast breast
feedingfeeding”” friendly society?friendly society?
65%
37%27% 28%
0%
20%
40%
60%
80%
1946 1956 1966 1972
Percentage of Women
Breastfeeding in the US
Field Studies of BreastfeedingField Studies of Breastfeeding
1212
Months
Lactation in the !KungLactation in the !Kung
•• Long interbirth intervals Long interbirth intervals
-- 44.1 44.1 mthsmths
•• Patterning of lactationPatterning of lactation
•• 4.06 bouts/hour4.06 bouts/hour
•• 7.83min/hour7.83min/hour
•• 1.92 min/bout1.92 min/bout
•• As child gets older As child gets older ——
increase in length increase in length
betweenbetween boutsbouts
Lactation in the !KungLactation in the !Kung
•• Lower estradiol and Lower estradiol and
progesterone in nursing progesterone in nursing
mothersmothers
Lactation in the !KungLactation in the !Kung
•• Lower estradiol and Lower estradiol and
progesterone in nursing progesterone in nursing
mothersmothers
•• Correlated with age of Correlated with age of
infant and mean time infant and mean time
between nursing boutsbetween nursing bouts
Lactation in the !KungLactation in the !Kung
•• Lower estradiol and Lower estradiol and
progesterone in nursing progesterone in nursing
mothersmothers
•• Correlated with age of Correlated with age of
infant and mean time infant and mean time
between nursing boutsbetween nursing bouts
•• Suggested interSuggested inter--bout bout
interval key variable in interval key variable in
lactation lactation subfecunditysubfecundity
(Konner & Worthman)
1313
Prolactin & Nursing Bout LengthProlactin & Nursing Bout Length
Prolactin
Nursing
Bout
Prolactin, # Nursing Bouts, & TimeProlactin, # Nursing Bouts, & Time
Prolactin threshold for ovulation
Edinburgh Study of BreastfeedingEdinburgh Study of Breastfeeding
Howie and McNeilly
Edinburgh StudyEdinburgh Study
•• Studied 27 breastfeeding Studied 27 breastfeeding and 10 bottle feeding and 10 bottle feeding mothersmothers
•• Lactation/supplementation Lactation/supplementation diariesdiaries
•• Measured urinary Measured urinary hormoneshormones
•• Measure prolactin in bloodMeasure prolactin in blood
Resumption of Ovarian FunctionResumption of Ovarian Function
1414
Supplementation & Ovarian FunctionSupplementation & Ovarian Function Resumption of Ovarian FunctionResumption of Ovarian Function
Edinburgh StudyEdinburgh Study
•• Lactating women resumed ovarian function later Lactating women resumed ovarian function later
postpartum than did bottle feeding womenpostpartum than did bottle feeding women
Edinburgh StudyEdinburgh Study
•• Lactating women resumed ovarian function later Lactating women resumed ovarian function later
postpartum than did bottle feeding womenpostpartum than did bottle feeding women
•• Frequency of ovulation increased with time as Frequency of ovulation increased with time as
lactation was phased outlactation was phased out
Edinburgh StudyEdinburgh Study
•• Lactating women resumed ovarian function later Lactating women resumed ovarian function later
postpartum than did bottle feeding womenpostpartum than did bottle feeding women
•• Frequency of ovulation increased with time as Frequency of ovulation increased with time as
lactation was phased outlactation was phased out
•• Rapid resumption of ovarian function in bottle Rapid resumption of ovarian function in bottle
feeders; gradual resumption in breast feedersfeeders; gradual resumption in breast feeders
Edinburgh StudyEdinburgh Study
•• Lactating women resumed ovarian function later Lactating women resumed ovarian function later
postpartum than did bottle feeding womenpostpartum than did bottle feeding women
•• Frequency of ovulation increased with time as Frequency of ovulation increased with time as
lactation was phased outlactation was phased out
•• Rapid resumption of ovarian function in bottle Rapid resumption of ovarian function in bottle
feeders; gradual resumption in breast feedersfeeders; gradual resumption in breast feeders
•• Importance of introduction of supplementary Importance of introduction of supplementary
foodsfoods
1515
Edinburgh StudyEdinburgh Study
•• Lactating women resumed ovarian function later Lactating women resumed ovarian function later
postpartum than did bottle feeding womenpostpartum than did bottle feeding women
•• Frequency of ovulation increased with time as Frequency of ovulation increased with time as
lactation was phased outlactation was phased out
•• Rapid resumption of ovarian function in bottle Rapid resumption of ovarian function in bottle
feeders; gradual resumption in breast feedersfeeders; gradual resumption in breast feeders
•• Importance of introduction of supplementary Importance of introduction of supplementary
foodsfoods
•• Women who conceived while nursing decreased Women who conceived while nursing decreased
the frequency to 3 or fewer times/day.the frequency to 3 or fewer times/day.
Lactation & Supplementation:Lactation & Supplementation:
The GambiaThe Gambia
Supplementation and Breast MilkSupplementation and Breast Milk
•• Gave 130 women supplement increased Gave 130 women supplement increased calories from 1568 to 2291 + vitamincalories from 1568 to 2291 + vitamin
•• No effect on breast milk volume!!No effect on breast milk volume!!
Supplementation and Breast MilkSupplementation and Breast Milk
•• Gave130 women supplement increased Gave130 women supplement increased calories from 1568 to 2291 + vitaminscalories from 1568 to 2291 + vitamins
•• No effect on breast milk volumeNo effect on breast milk volume
•• Protein content slightly increased (6.6%)Protein content slightly increased (6.6%)
•• Milk fat increase (7.9%)Milk fat increase (7.9%)
•• Lactose decrease (Lactose decrease (--7.6%)7.6%)
•• No change in caloriesNo change in calories
•• Vitamin increase from supplementVitamin increase from supplement
Prolactin & SupplementationProlactin & Supplementation
1616
Gambian StudyGambian Study
•• Supplementation had only a small effect on Supplementation had only a small effect on
quantity and quality of breast milkquantity and quality of breast milk
•• Supplementation had a dramatic effect on Supplementation had a dramatic effect on
prolactin levelsprolactin levels
Prolactin Prolactin && Lactational Lactational
AmenorrheaAmenorrhea
•• High levels ofHigh levels of prolactin prolactin associated with associated with
reduced ability for egg to producereduced ability for egg to produce estradiol estradiol
(in culture)(in culture)
•• Evidence now is role may be more indirect.Evidence now is role may be more indirect.
The Toba: Positive Energy Balance The Toba: Positive Energy Balance
and High Nursing Frequencyand High Nursing FrequencyBreast Feeding HypothesesBreast Feeding Hypotheses
•• How to explain variation in duration of How to explain variation in duration of
postpartum period of infecunditypostpartum period of infecundity
•• Nursing Intensity HypothesisNursing Intensity Hypothesis
•• Metabolic Load HypothesisMetabolic Load Hypothesis
Valeggia & Ellison
Nursing Intensity Hypothesis
1717
Nursing intensity hypothesis:Nursing intensity hypothesis:
The more intensive the nursing, the longer the period The more intensive the nursing, the longer the period
of of lactational lactational amenorrheaamenorrhea
Relative metabolic load hypothesis:
The higher the relative cost of nursing, the longer the period of lactational
amenorrhea
1818
Physical activity postpartumPhysical activity postpartum
0
20
40
60
80
Sitting
Standing
Walking
Crouch/Bend
Walk w/load
Laying down
Chop wood
% of observation points .
(Valeggia &
Ellison 2003)
n = 70 women
Focal sampling
10
15
20
25
30
35
1 3 5 7 9 11 13 15 17 19
Month Post-partum
Mean BMI (± SD)
Toba Toba women remain wellwomen remain well--nourished nourished
during the entire postpartum periodduring the entire postpartum period
Valeggia & Ellison (2003)
WHO’s “normal” range
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
-15-14-13-12-11-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3
Months to 1st menses
Mean ∆BMI (± SE)
Valeggia & Ellison (2003)
Changes in energy balance in relation to
time to first postpartum menses
First menses
Average n = 45
Negative
energy balance
Positive energy balance
1919
Mean duration of postpartum amenorrhea Mean duration of postpartum amenorrhea
1010 ((±± 4) months 4) months (n = 122(n = 122))
!Kung-like nursing intensity
US-like nutritional status
Lactational Lactational Amenorrhea in TobaAmenorrhea in Toba
•• Mean = 10.3 monthsMean = 10.3 months
Valeggia & Ellison
Lactational Lactational Amenorrhea in TobaAmenorrhea in Toba
•• Mean = 10.3 monthsMean = 10.3 months
•• High nutritional status and high nursing High nutritional status and high nursing
intensity intensity —— leads to short periods of leads to short periods of
lactational lactational amenorrheaamenorrhea
Valeggia & Ellison
Lactational Lactational Amenorrhea in TobaAmenorrhea in Toba
•• Mean = 10.3 monthsMean = 10.3 months
•• High nutritional status and high nursing High nutritional status and high nursing
intensity intensity —— leads to short periods of leads to short periods of
lactational lactational amenorrheaamenorrhea
•• Thus, nursingThus, nursing intensity alone is insufficient intensity alone is insufficient
explanationexplanation
Valeggia & Ellison
Lactational Lactational Amenorrhea in TobaAmenorrhea in Toba
•• Mean = 10.3 monthsMean = 10.3 months
•• High nutritional status and high nursing High nutritional status and high nursing intensity intensity —— leads to short periods of leads to short periods of lactational lactational amenorrheaamenorrhea
•• Thus, nursingThus, nursing intensity alone is insufficient intensity alone is insufficient explanationexplanation
•• Interaction between nursing intensity and Interaction between nursing intensity and nutritional statusnutritional status
Valeggia & Ellison
Next time ...Next time ...
•• MotherMother--Infant BondingInfant Bonding
•• Fatherhood and changes in Fatherhood and changes in
paternal hormonespaternal hormones
•• CoCo--sleeping and SIDSsleeping and SIDS
•• Parenting styles crossParenting styles cross--
culturallyculturally
2020
Field Studies of BreastfeedingField Studies of BreastfeedingProximate determinants Proximate determinants
of of lactational lactational amenorrheaamenorrhea
Toba Toba women nurse their infants very women nurse their infants very
frequentlyfrequently
0
1
2
3
4
5
6
7
8
1-3 4-6 7-9 10-12 12-15
Age of infant (months)
Valeggia & Ellison (2003)
n = 70
Nursing events durationNursing events duration
0
1
2
3
4
1-3 4-6 7-9 10-12 13-15
Age of the infant (months)
Mean event duration
in min (±SD)
Valeggia & Ellison (2003)
Maternal dietMaternal diet
•• One main meal + snacksOne main meal + snacks
•• Monotonous, calorieMonotonous, calorie--dense dietdense diet
•• Rich in complex carbohydrates and fats Rich in complex carbohydrates and fats
(e.g., fried dough, white bread, noodles, (e.g., fried dough, white bread, noodles,
rice, polenta)rice, polenta)
Determinants of durationDeterminants of duration
of of lactational lactational amenorrheaamenorrhea
•• No association with nursing behavior (frequency, No association with nursing behavior (frequency, duration of individual bouts, total duration of duration of individual bouts, total duration of nursing, all regression p > 0.11)nursing, all regression p > 0.11)
•• No association with No association with staticstatic measures of measures of
maternal maternal energeticsenergetics (e.g., pre(e.g., pre--
pregnancy BMI, average postpartum pregnancy BMI, average postpartum
BMI, BMI at time of 1BMI, BMI at time of 1stst menses, % fat; menses, % fat;
all all pp’’ss > 0.09)> 0.09)
2121
Significant correlation with dynamic, time-dependent measures of maternal energetics (e.g, postpartum energy
balance)
ConclusionConclusion
The pattern of resumption of The pattern of resumption of
postpartum fertility could be postpartum fertility could be
explained by differences in explained by differences in individual individual
metabolic budgetsmetabolic budgets..