lecture 15: pregnancy - harvard universitysites.fas.harvard.edu/~anth1380/slides/lecture 15.pdf ·...

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Lecture 15: Pregnancy Lecture 15: Pregnancy

•• Gestational DevelopmentGestational Development

•• Early development and the Early development and the

placentaplacenta

•• Maternal/fetal conflictMaternal/fetal conflict

•• The Physiology of The Physiology of

PregnancyPregnancy

•• Pica eatingPica eating

•• Pregnancy SicknessPregnancy Sickness

The Behavioral Biology of Women-2006

22

Exercise during Pregnancy Exercise during Pregnancy

and Miscarriageand Miscarriage

0

4

8

12

16

20

Frequency of Miscarriage

Exercise Non-Exercise

(Clapp, 2002)

Stages of DevelopmentStages of Development

•• Conceptus Conceptus (morula & blastocyte)(morula & blastocyte)

•• EmbryoEmbryo

•• FetusFetus

•• EmbryogenesisEmbryogenesis

•• Embryonic PhaseEmbryonic Phase

•• Fetal PhaseFetal Phase

•• Weeks 0Weeks 0--22



EmbryogenesisEmbryogenesis

•• Conceptus Conceptus

(morulla & blastocyte) (morulla & blastocyte)

•• First 14First 14--16 days = 16 days =

formation of an embryoformation of an embryo


•• Conceptus Conceptus (morulla & blastocyte) (morulla & blastocyte)

•• First 14First 14--16 days = 16 days = formation of an embryoformation of an embryo

•• Histiotropic nutritionHistiotropic nutrition --relies on uterine secretions relies on uterine secretions for oxygen and metabolic for oxygen and metabolic substratessubstrates


•• ConceptusConceptus

•• First 14First 14--16 days = 16 days = formation of an embryoformation of an embryo

•• Histiotropic nutrition Histiotropic nutrition --relies on uterine secretions relies on uterine secretions for oxygen and metabolic for oxygen and metabolic substratessubstrates

•• Differentiation into Differentiation into embryonic (inner cell embryonic (inner cell mass) and extramass) and extra--embryonic embryonic tissue (trophoblast)tissue (trophoblast)

33

Implantation: Actions of BlastocyteImplantation: Actions of Blastocyte

•• (1) Blastocyte establishes physical and (1) Blastocyte establishes physical and

nutritional contact with maternal nutritional contact with maternal

endometriumendometrium

Blastocyte Embedded in Uterine Lining

Haemotrophic Nutrition =

Nutrition from the maternal

blood supply

Establishment of the PlacentaEstablishment of the Placenta

•• Digestion of Digestion of

maternal tissue to maternal tissue to

release metabolic release metabolic

substratessubstrates

•• Primary Primary

Decidualization Decidualization

ReactionReaction

Species Differences in PlacentasSpecies Differences in Placentas

Human (discoid)Mouse, rabbit, bat Cat, seal, elephant ,bear (zonary)

Cow, sheep, giraffe (cotyledonary) Horse, whale, kangaroo (diffuse)

•• (2) Trophoblast (2) Trophoblast

starts to produce starts to produce

HCG (Human HCG (Human

Chorionic Chorionic

Gonadotrophin) Gonadotrophin)

to keep corpus to keep corpus

luteum aliveluteum alive

Implantation: Actions of Implantation: Actions of

BlastocyteBlastocyte

Expression of HCG during human pregnancyExpression of HCG during human pregnancy

44

Embryonic PhaseEmbryonic Phase

(Weeks 3(Weeks 3--8)8)

•• Formation of basic body planFormation of basic body plan

•• Development of all major organ systemsDevelopment of all major organ systems

5 Weeks

6 Weeks

7 Weeks

Fetal PhaseFetal Phase

(Weeks 9(Weeks 9--38)38)

•• Growth and further development of body Growth and further development of body

tissues and organs.tissues and organs.

55

9 Weeks

13 Weeks

21 Weeks

Russell at 3 monthsRussell at 3 months

THE PHYSIOLOGY OF THE PHYSIOLOGY OF

PREGNANCYPREGNANCY

Corpus Luteum

66

Corpus LuteumCorpus Luteum

•• Produces increasing amounts of Produces increasing amounts of

progesteroneprogesterone

•• Synthesizes estrogenSynthesizes estrogen

•• Important for production until 6Important for production until 6--

7 weeks of pregnancy7 weeks of pregnancy

•• If embryo canIf embryo can’’t maintain hormone t maintain hormone

production often results in miscarriage at production often results in miscarriage at

this time.this time.

•• Helps maintain early pregnancyHelps maintain early pregnancy

The Role of the FetusThe Role of the Fetus

The Placenta The Placenta -- ““baby sidebaby side”” The Placenta The Placenta -- ““mother sidemother side””

Human Haemomonochorial Human Haemomonochorial

PlacentaPlacenta

•• ExtraExtra--embryonic embryonic

tissue, containing fetal tissue, containing fetal

blood vessels, blood vessels,

penetrates deep into penetrates deep into

maternal tissuematernal tissue

77


Placenta Placenta -- Terminal villusTerminal villus

•• Tips of capillaries Tips of capillaries

form tortuous loops form tortuous loops ----

slowing blood flow slowing blood flow

and allowing for and allowing for

exchange of exchange of

metabolites with metabolites with

maternal blood.maternal blood.


PlacentaPlacenta

•• Maternal spiral artery Maternal spiral artery

ejects blood into ejects blood into

‘‘maternal blood maternal blood

spacespace’’

Pregnancy ConflictsPregnancy Conflicts HamiltonHamilton’’s Rules Rule

You are related to yourself by 100%, You are related to yourself by 100%,

to your children your siblings and to your children your siblings and

your parents by 50%, etc.your parents by 50%, etc.

88

Pregnancy Pregnancy ““ConflictsConflicts””

•• Paternal genes will be Paternal genes will be

selected to increase the selected to increase the

transfer of nutrients to transfer of nutrients to

the fetusthe fetus

•• Maternal genes will be Maternal genes will be

selected to limit selected to limit

transfers in excess of transfers in excess of

some maternal some maternal

optimumoptimum

Haig, 1993

Monogenetic Mouse Embryos

Control Gynogenetic Androgenetic

Embryo

Yolk Sac

Trophoblast

Supporting EvidenceSupporting Evidence•• Trophoblast invades maternal Trophoblast invades maternal

endometrium and remodels the endometrium and remodels the

spiral arteries so they are spiral arteries so they are

unable to constrictunable to constrict





–– Fetus gains access to motherFetus gains access to mother’’s s

arterial blood & mother canarterial blood & mother can’’t t

change nutrient content of bloodchange nutrient content of blood








–– Volume of blood reaching Volume of blood reaching

placenta not under maternal placenta not under maternal

controlcontrol










controlcontrol

–– Placenta is able to release Placenta is able to release

hormones directly into maternal hormones directly into maternal

circulationcirculation

99










controlcontrol

–– Placenta is able to release Placenta is able to release

hormones directly into maternal hormones directly into maternal

circulationcirculation

•• High HCG levelsHigh HCG levels

Trend toward increased hormone Trend toward increased hormone

production?production?

•• Increase from 1 CGIncrease from 1 CGββ gene in gene in

Anthropoid Ancestor to 6 in humanAnthropoid Ancestor to 6 in human

•• Increase from 1 OIncrease from 1 O--linked sugar chain in linked sugar chain in

Anthropoid Ancestor to 4 in humanAnthropoid Ancestor to 4 in human

•• Increase from 1 CRE element in Increase from 1 CRE element in

Ancestral Ancestral αα promoter to 2 in humanpromoter to 2 in humanMaston, 2000

Increase in number of genes responsible for Increase in number of genes responsible for

hormonal production in Humanshormonal production in Humans

Hormonal Production in Hormonal Production in

the Placentathe Placenta

•• EstrogenEstrogen

•• ProgesteroneProgesterone

•• HCG (Human Chorionic Gonadotropin)HCG (Human Chorionic Gonadotropin)

•• HPL (Human Placental Lactogen)HPL (Human Placental Lactogen)

Fetoplacental UnitFetoplacental Unit

•• Placenta converts androgens from the Placenta converts androgens from the

adrenal gland of the fetus (as well as the adrenal gland of the fetus (as well as the

mother) into estrogen.mother) into estrogen.

Fetal Adrenal GlandsFetal Adrenal Glands

•• Fetal adrenal is the largest organ in the Fetal adrenal is the largest organ in the

babybaby’’s body (adult size) and produces 10 s body (adult size) and produces 10

times the amount of hormones as an adult.times the amount of hormones as an adult.

Estrogens and the Fetoplacental UnitEstrogens and the Fetoplacental Unit




1010

Estrogen & the Fetoplacental UnitEstrogen & the Fetoplacental Unit




•• Estrogen causes changes in the uterus, Estrogen causes changes in the uterus,

cervix, vagina and breasts and affects cervix, vagina and breasts and affects

metabolism.metabolism.

The Placenta: ProgesteroneThe Placenta: Progesterone

•• Takes over progesterone production from Takes over progesterone production from

the Corpus Luteumthe Corpus Luteum


•• Takes over progesterone Takes over progesterone

production from the Corpus production from the Corpus

LuteumLuteum

•• Levels are 10 times as high as Levels are 10 times as high as

before fertilizationbefore fertilization


•• Takes over progesterone production from Takes over progesterone production from

the Corpus Luteumthe Corpus Luteum

•• Levels are 10 times as high as before Levels are 10 times as high as before

fertilizationfertilization

•• Keeps uterus from contractingKeeps uterus from contracting


•• Takes over progesterone Takes over progesterone

production from the Corpus production from the Corpus

LuteumLuteum

•• Levels are 10 times as high as Levels are 10 times as high as

before fertilizationbefore fertilization

•• Keeps uterus from contractingKeeps uterus from contracting

•• Maintains blood vessels and Maintains blood vessels and

glands in uterine liningglands in uterine lining

The Placenta: HCGThe Placenta: HCG

•• Keeps Corpus Keeps Corpus

Luteum from Luteum from

shrinking.shrinking.

1111

The Placenta: HCGThe Placenta: HCG

•• Keeps Corpus Keeps Corpus

Luteum from Luteum from

shrinking.shrinking.

•• Production rises Production rises

steeply after steeply after

implantationimplantation

The Placenta: HPLThe Placenta: HPL

(Human Placental Lactogen)(Human Placental Lactogen)

•• Alters motherAlters mother’’s metabolism to make sugar s metabolism to make sugar

and proteins more available to fetusand proteins more available to fetus

The Placenta: HPLThe Placenta: HPL

•• Alters motherAlters mother’’s metabolism to make sugar s metabolism to make sugar

and proteins more available to fetusand proteins more available to fetus

•• Stimulates alveoli in motherStimulates alveoli in mother’’s breasts to s breasts to

develop and prepare for lactationdevelop and prepare for lactation

Hormonal changes during Pregnancy

Species Species

Differences in Differences in

Pregnancy Pregnancy

HormonesHormones

Hominoid Hominoid

Pregnancy Pregnancy

HormonesHormones

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Changes in the motherChanges in the mother Changes in UterusChanges in Uterus

•• Uterus grows to 500Uterus grows to 500--

1000 times in size1000 times in size

Changes in UterusChanges in Uterus

•• Uterus grows to Uterus grows to

500500--1000 times in 1000 times in

sizesize

•• New muscles fibers New muscles fibers

are produced.are produced.

Changes in SkeletonChanges in Skeleton

•• Increased spinal Increased spinal

curvaturecurvature

Changes in SkeletonChanges in Skeleton

•• Increased spinal Increased spinal

curvaturecurvature

•• Loosening of jointsLoosening of joints

Digestive SystemDigestive System

•• Uterus pushes intestines Uterus pushes intestines

& stomach up to the & stomach up to the

sideside

1313




sideside

•• Shift in stomach causes Shift in stomach causes

change in angle of change in angle of

esophagusesophagus——heartburnheartburn




sideside

•• Shift in stomach causes Shift in stomach causes

change in angle of change in angle of

esophagusesophagus——heartburnheartburn

•• High progesteroneHigh progesterone--

increased transit timeincreased transit time

Urinary Tract ChangesUrinary Tract Changes

•• Kidneys process 50% Kidneys process 50%

increase in wasteincrease in waste




•• Slower transit time Slower transit time

(smooth muscle slowed (smooth muscle slowed

down by progesterone)down by progesterone)







•• Urinary Tract InfectionsUrinary Tract Infections







•• Urinary Tract InfectionsUrinary Tract Infections

•• Compression of bladderCompression of bladder

1414

Changes during PregnancyChanges during Pregnancy

•• Gums may bleed Gums may bleed —— blood blood

vessel stimulation caused by vessel stimulation caused by

high estrogenhigh estrogen

Changes during PregnancyChanges during Pregnancy

•• Hemorrhoids and varicose veins Hemorrhoids and varicose veins

may developmay develop

•• Gums may bleed Gums may bleed —— blood blood

vessel stimulation caused by vessel stimulation caused by

high estrogenhigh estrogen

Heart ChangesHeart Changes

•• Heart works harder. Heart works harder.

Pulse increases by 10Pulse increases by 10--

15 beat/min15 beat/min

Heart ChangesHeart Changes

•• Heart works harder. Pulse Heart works harder. Pulse

increases by 10increases by 10--15 beat/min15 beat/min

•• Total cardiac output increased Total cardiac output increased

by 30%by 30%

Lung ChangesLung Changes

•• Lungs compressedLungs compressed



•• Rib cage flares up and outRib cage flares up and out

1515



•• Rib cage flares up and outRib cage flares up and out

•• Lungs bring in 40% more air.Lungs bring in 40% more air.

Changes During PregnancyChanges During Pregnancy

•• Separation of rectus abdominus muscle (diastesis)Separation of rectus abdominus muscle (diastesis)

Immune SystemImmune System

•• Placenta keeps Placenta keeps

babybaby’’s cells from s cells from

entering blood entering blood

streamstream


•• Placenta keeps babyPlacenta keeps baby’’s s

cells from entering cells from entering

blood streamblood stream

•• Progesterone slows Progesterone slows

down antibody down antibody

productionproduction


•• Placenta keeps babyPlacenta keeps baby’’s cells s cells

from entering blood streamfrom entering blood stream

•• Progesterone slows down Progesterone slows down

antibody productionantibody production

•• Baby produces surface Baby produces surface

repellent molecules that repellent molecules that

cross placenta and coat cross placenta and coat

mothermother’’s lymphocytess lymphocytes

Breast ChangesBreast Changes•• Increased engorgement Increased engorgement

caused by estrogen and caused by estrogen and


•• TendernessTenderness

1616




–– TendernessTenderness

•• Size increaseSize increase






•• Alveoli increaseAlveoli increase







•• Striae visibleStriae visible








•• NippleNipple--larger, darker, larger, darker,

more erectilemore erectile










•• Areola darkensAreola darkens










•• Areola darkensAreola darkens

•• Colostrum productionColostrum production

1717

The VaginaThe Vagina

•• VaginaVagina——increased blood flow increased blood flow

and softeningand softening



and softening.and softening.

•• Walls thicken, looser, elongatesWalls thicken, looser, elongates





•• Increased dischargeIncreased discharge——acidic acidic

prevents infectionprevents infection





•• Increased dischargeIncreased discharge——prevents prevents

infectioninfection

•• Blood vessels in uterus, vagina Blood vessels in uterus, vagina

and pelvic area enlarge and and pelvic area enlarge and

increase in numberincrease in number

The CervixThe Cervix

•• Increases blood Increases blood

vessels and mucous vessels and mucous

glandsglands

The CervixThe Cervix

•• Increases blood Increases blood

vessels and mucous vessels and mucous

glandsglands

•• Formation of mucous Formation of mucous

plugplug

1818

Changes in SexualityChanges in Sexuality

•• Increased blood flow may result in Increased blood flow may result in

increased sexual arousalincreased sexual arousal




•• May be more easily arousedMay be more easily aroused




•• May be more easily arousedMay be more easily aroused

•• May have multiple orgasmsMay have multiple orgasms

Changes in PigmentationChanges in Pigmentation•• High levels of High levels of

melanocyte melanocyte

stimulating hormonestimulating hormone




•• Progesterone and Progesterone and

estrogen stimulate estrogen stimulate

pigment cellspigment cells






pigment cells pigment cells

•• ““Linea nigraLinea nigra””

1919








•• ChloasmaChloasma——““mask mask

of pregnancyof pregnancy””










•• Nipples & Areola Nipples & Areola

darkendarken











darkendarken •• Stretch marksStretch marks











darkendarken

•• Stretch marksStretch marks

•• ““Vascular spidersVascular spiders””

on face, chest, armson face, chest, arms

Changes in Blood VolumeChanges in Blood Volume

•• Blood volume increases Blood volume increases

by 50by 50--100%100%

Changes in Blood VolumeChanges in Blood Volume

•• Blood volume increases Blood volume increases

by 50by 50--100%100%

–– Fills blood reservoir of Fills blood reservoir of

uterusuterus

–– Protects baby from drop Protects baby from drop

in b.p.in b.p.

–– Prepare mother for Prepare mother for

childbirthchildbirth

__ estrogen causes increase estrogen causes increase

in blood clotting factorsin blood clotting factors

2020

Sources of Weight GainSources of Weight Gain Charlotte BronteCharlotte Bronte

Studies of

Pregnancy

Sickness(NVP,

Nausea and

Vomiting

during

Pregnancy)

Pregnancy Sickness and Pregnancy Sickness and

Hormonal LevelsHormonal Levels

•• Higher levels of Higher levels of

HCG associated HCG associated

with increased with increased

nausea, vomiting, nausea, vomiting,

food aversion and food aversion and

smell aversionsmell aversion

•• Higher levels of HCG Higher levels of HCG associated with associated with increased nausea, increased nausea, vomiting, food aversion vomiting, food aversion and smell aversionand smell aversion

•• HCG peaks at 8HCG peaks at 8--10 10 weeks weeks ——parallels parallels pregnancy sicknesspregnancy sickness



•• Higher levels of HCG Higher levels of HCG associated with increased associated with increased nausea, vomiting, food nausea, vomiting, food aversion and smell aversionaversion and smell aversion

•• HCG peaks at 8HCG peaks at 8--10 weeks 10 weeks ——parallels pregnancy sicknessparallels pregnancy sickness

•• Increased Estrogen/Decreased Increased Estrogen/Decreased Progesterone ratio: Increased Progesterone ratio: Increased food avoidance, smell food avoidance, smell aversionaversion



2121

•• Higher levels of HCG associated Higher levels of HCG associated with increased nausea, vomiting, with increased nausea, vomiting, food aversion and smell aversionfood aversion and smell aversion


•• Increased Increased Estrogen/Decreased Estrogen/Decreased Progesterone ratio: Increased Progesterone ratio: Increased food avoidance, smell food avoidance, smell aversionaversion

•• Ratio not related to nausea or Ratio not related to nausea or vomitingvomiting



•• Higher levels of HCG associated Higher levels of HCG associated with increased nausea, vomiting, with increased nausea, vomiting, food aversion and smell aversionfood aversion and smell aversion


•• Increased Estrogen/Decreased Increased Estrogen/Decreased Progesterone ratio: Increased food Progesterone ratio: Increased food avoidance, smell aversionavoidance, smell aversion

•• Ratio not related to nausea or Ratio not related to nausea or vomitingvomiting

•• Decrease in symptoms with Decrease in symptoms with increased maternal ageincreased maternal age



Pregnancy Sickness HypothesisPregnancy Sickness Hypothesis

•• Food aversions, nausea Food aversions, nausea and vomiting of and vomiting of pregnancy sickness pregnancy sickness protect embryo against protect embryo against maternal ingestion of maternal ingestion of teratogens and teratogens and abortifacients that are abortifacients that are abundant in natural abundant in natural foods.foods.

Profet, 1990

Pregnancy Sickness HypothesisPregnancy Sickness Hypothesis•• Food aversions, nausea and Food aversions, nausea and

vomiting of pregnancy vomiting of pregnancy

sickness protect embryo sickness protect embryo

against maternal ingestion of against maternal ingestion of

teratogens and abortifacients teratogens and abortifacients

that are abundant in natural that are abundant in natural

foods.foods.

•• Lowering of the normal Lowering of the normal

human threshold of tolerance human threshold of tolerance

to toxins to compensate for to toxins to compensate for

extreme vulnerability of extreme vulnerability of

embryoembryo Profet, 1990

Pregnancy SicknessPregnancy Sickness

•• Foods that are safely Foods that are safely

ingested by adults ingested by adults

contain compounds contain compounds

that induce fetal that induce fetal

malformationsmalformations



ingested by adults ingested by adults

contain compounds contain compounds

that induce fetal that induce fetal


•• Women with Women with

pregnancy sickness pregnancy sickness

avoid foods that emit avoid foods that emit

cues associated with cues associated with

toxicitytoxicity

2222



ingested by adults contain ingested by adults contain

compounds that induce compounds that induce

fetal malformationsfetal malformations

•• Women with pregnancy Women with pregnancy

sickness avoid foods that sickness avoid foods that

emit cues associated with emit cues associated with

toxicitytoxicity

•• Pregnancy sickness Pregnancy sickness

begins when the begins when the

embryo becomes embryo becomes

vulnerable to toxinsvulnerable to toxins


•• Foods that are safely ingested Foods that are safely ingested

by adults contain compounds by adults contain compounds

that induce fetal malformationsthat induce fetal malformations

•• Women with pregnancy Women with pregnancy

sickness avoid foods that emit sickness avoid foods that emit

cues associated with toxicitycues associated with toxicity

•• Pregnancy sickness begins when Pregnancy sickness begins when

the embryo becomes vulnerable the embryo becomes vulnerable

to toxinsto toxins

•• Olfactory system changes Olfactory system changes

during pregnancy in ways during pregnancy in ways

that promote selective that promote selective

avoidanceavoidance


•• Foods that are safely ingested by adults Foods that are safely ingested by adults

contain compounds that induce fetal contain compounds that induce fetal


•• Women with pregnancy sickness avoid Women with pregnancy sickness avoid

foods that emit cues associated with foods that emit cues associated with

toxicitytoxicity

•• Pregnancy sickness begins when the Pregnancy sickness begins when the

embryo becomes vulnerable to toxinsembryo becomes vulnerable to toxins

•• Olfactory system changes during Olfactory system changes during

pregnancy in ways that promote pregnancy in ways that promote

selective avoidanceselective avoidance

•• Women with pregnancy sickness Women with pregnancy sickness

have better pregnancy outcomeshave better pregnancy outcomes


•• Foods that are safely ingested by adults Foods that are safely ingested by adults

contain compounds that induce fetal contain compounds that induce fetal


•• Women with pregnancy sickness avoid foods Women with pregnancy sickness avoid foods

that emit cues associated with toxicitythat emit cues associated with toxicity

•• Pregnancy sickness begins when the embryo Pregnancy sickness begins when the embryo

becomes vulnerable to toxinsbecomes vulnerable to toxins

•• Olfactory system changes during pregnancy in Olfactory system changes during pregnancy in

ways that promote selective avoidanceways that promote selective avoidance

•• Women with pregnancy sickness have better Women with pregnancy sickness have better

pregnancy outcomespregnancy outcomes

•• Pregnancy sickness is crossPregnancy sickness is cross--culturalcultural

Test of Profet HypothesisTest of Profet Hypothesis

(Flaxman & Sherman, 2000)

Does morning sickness

protect the embryo by

causing pregnant women

to physically expel and

subsequently avoid foods

that contain teratogenic

and abortifacient

chemicals?

Test of Profet HypothesisTest of Profet Hypothesis• Symptoms peak when embryonic organogenesis is most susceptible to chemical disruption (weeks 6-18)


2323


• Women who experience morning sickness are significantly less likely to miscarry than women who do not (9 of 9 studies)



• Women who experience morning sickness are significantly less likely to miscarry that women who do not (9 of 9 studies)

• Women who vomit suffer fewer miscarriages than those who experience nausea alone





• Many pregnant women have aversions to alcoholic and nonalcoholic (mostly caffeinated) beverages and strong-tasting vegetables, especially during the first trimester.





• Many pregnant women have aversions to alcoholic and nonalcoholic (mostly caffeinated) beverages and strong-tasting vegetables, especially during the first trimester.

• However, greatest aversions are to meat, fish, poultry and eggs.


CrossCross--Cultural Survey of Cultural Survey of

Morning Sickness IncidenceMorning Sickness Incidence

0

2

4

6

8

10

12

14

16

18

20

Number of Societies

NVP Observed NVP Never Observed

More meat

consumption

Less meat

consumption


Pregnancy Sickness and Avoidance ofPregnancy Sickness and Avoidance of

Food Borne PathogensFood Borne Pathogens


•• Pregnant women are immunosuppressed Pregnant women are immunosuppressed

and thus more vulnerable to serious and thus more vulnerable to serious

infections.infections.

•• Thus, pregnancy sickness evolved to avoid Thus, pregnancy sickness evolved to avoid

food borne parasites and pathogens that food borne parasites and pathogens that

might be dangerous.might be dangerous.

•• Differs from Profet by (1) focusing on Differs from Profet by (1) focusing on

toxins in meat not teratogens in plants (2) toxins in meat not teratogens in plants (2)

avoidance of infection not birth defectsavoidance of infection not birth defects

2424

Next TimeNext Time……

•• Energetics of pregnancyEnergetics of pregnancy

•• BirthBirth

•• Evolution of human birthEvolution of human birth

•• Birth practices in other Birth practices in other

culturescultures

lecture 15: pregnancy - harvard universitysites.fas.harvard.edu/~anth1380/slides/lecture 15.pdf ·...

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