Physiology of Pregnancy

Department of Department of PhysiologyPhysiology

School of MedicineSchool of MedicineUniversity of University of

Sumatera UtaraSumatera Utara

Endometrium Endometrium ddand and

D idD idDesiduaDesidua

3 days to move to uterus 3 -5 days in uterus before implantation

• Implantation results from the actionf t h bl t ll th t d lof trophoblast cells that develop

over the surface of the blastocyst.

• These cells secrete proteolyticenzymes that digest and liquefy theadjacent cells of the uterineadjacent cells of the uterineendometrium.

O i l t ti h t k l• Once implantation has taken place,the trophoblast cells and otheradjacent cells (from the blastocystand the uterine endometrium)proliferate rapidly, forming theplacenta and the variousplacenta and the variousmembranes of pregnancy.

ImplantationImplantation

FollowingFollowing implantationimplantation thethe endometriumendometrium isis knownknown asas thethe deciduadeciduaandand consistsconsists ofof threethree regionsregions:: thethe deciduadecidua basalis,basalis, deciduadeciduagg ,,

capuslaris,capuslaris, andand deciduadecidua parietalisparietalis..

TheThe deciduadecidua basalisbasalis lieslies betweenbetween thethe chorionchorion andand thethe stratumstratum basalisbasalis ofofTheThe deciduadecidua basalisbasalis lieslies betweenbetween thethe chorionchorion andand thethe stratumstratum basalisbasalis ofofthethe uterusuterus.. ItIt becomesbecomes thethe maternalmaternal partpart ofof thethe placentaplacenta..

TheThe deciduadecidua capsulariscapsularis coverscovers thethe embryoembryo andand isis locatedlocated betweenbetween thetheTheThe deciduadecidua capsulariscapsularis coverscovers thethe embryoembryo andand isis locatedlocated betweenbetween thetheembryoembryo andand thethe uterineuterine cavitycavity..

TheThe d cidud cidu p ri t lisp ri t lis lineslines thethe nonin ol ednonin ol ed areasareas ofof thethe entireentireTheThe deciduadecidua parietalisparietalis lineslines thethe noninvolvednoninvolved areasareas ofof thethe entireentirepregnantpregnant uterusuterus..

DeciduaDecidua

• When the conceptus implants in theendometrium, the continuedsecretion of progesterone causesthe endometrial cells to swell furtherand to store even more nutrientsand to store even more nutrients.

• These cells are now calleddecidual cells, and the total massof cells is called the decidua. Asthe trophoblast cells invade thedecidua digesting and imbibing itdecidua, digesting and imbibing it,the stored nutrients in the deciduaare used by the embryo for growthand development.

• Figure 82–4 shows this trophoblasticperiod of nutrition which graduallyperiod of nutrition, which graduallygives way to placental nutrition.

Medical Physiology, Guyton 6 ed, 2006, p.1029

ImplantationPlacental implantation in humansbegins with invasion of the uterineepithelium and underlying stromaepithelium and underlying stromaby extraembryonic trophoblastcells

Villous cytotrophoblast cells at thetips of some anchoring villiproliferate outwards from theunderlying basement membrane toform columns, from whichindividual cells migrate into thegdecidual tissueThese interstitial trophoblast cellsinvade as far as the superficialade as a as t e supe c alayer of the myometrium.

ImplantationTrophoblast cells invde into the uterine wall.

The trophoblast differentiatesThe trophoblast differentiates along two main pathway : Villous and extravillous

Villous trophoblast includes theVillous trophoblast includes the villous tree, which is bathed in maternal blood in intervillous spacespace

Extravillous trophoblast (EVT) encompasses all the invading subpopulation of trophoblastsubpopulation of trophoblast

EVT cells arise during early development as cyttrophoblast

Celss from the cytotrophoblastalso give arise to endovasculart h bl ttrophoblast.

At the same time, groups oftrophoblast cells detach from thetrophoblast cells detach from thecolumns to invade the lumen ofthe spiral arteries as

d l t h bl tendovascular trophoblast

The dramatic structural alterationof muscular spirl arteries intoof muscular spirl arteries intodilated sac-like vessel,unresponsive to vasocontrictiveagents and capable of highconcuctance, are essential toaccommodate the huge increasegin the blood flow required to theintervillous space

• During early human pregnancy, extravillous cytotrophoblasts from

anchoring villi invade the decidualized endometrium and myometriumanchoring villi invade the decidualized endometrium and myometrium

(interstitial trophoblasts) and also migrate in a retrograde direction

along the spiral arteries (endovascular trophoblasts) transforming themg p ( p ) g

into large diameter conduit vessels of low resistance.

• Endovascular trophoblast invasion has been reported to occur in two• Endovascular trophoblast invasion has been reported to occur in two

waves; the first into the decidual segments of spiral arteries at 8 to 10

weeks of gestation and the second into myometrial segments at 16 tog y g

18 weeks of gestation.

• This physiological transformation is characterized by a gradual loss of• This physiological transformation is characterized by a gradual loss of

the normal musculoelastic structure of the arterial wall and

replacement by amorphous fibrinoid material in which trophoblast cellsy

are embedded. These physiological changes are required for a

successful pregnancy.

ImplantationChorionic Villi:

Finger-like growths of the trophoblasts into the

This vascular transformation is

important to ensure an adequate blood

endometrium to form the placenta

supply to the feto–placental unit.

Failure of this process lead to clinical

pathological conditions such as

miscarriage, intrauterine growth

retardation or preeclamptic toxaemia.

ImplantationImplantationViability of the corpus luteum is maintained by human Viability of the corpus luteum is maintained by human chorionic gonadotropin (hCG) secreted by the chorionic gonadotropin (hCG) secreted by the

bbtrophoblaststrophoblastshCG prompts the corpus luteum to continue to secrete hCG prompts the corpus luteum to continue to secrete progesterone and estrogenprogesterone and estrogenChorion Chorion –– developed from trophoblasts after developed from trophoblasts after implantation, continues this hormonal stimulusimplantation, continues this hormonal stimulusBetween the second and third month, the placenta: Between the second and third month, the placenta:

Assumes the role of progesterone and estrogen Assumes the role of progesterone and estrogen productionproductionIs providing nutrients and removing wastesIs providing nutrients and removing wastes

• Chorion:– Outermost embryonic membrane which

forms the placenta & produces human chorionic gonadotropinchorionic gonadotropin.

• Amnion:– Membrane which surrounds embryo to

form the amniotic cavity & produces amniotic fluidamniotic fluid.

• Amnionic Fluid:– Protects fetus from trauma & permits free

movement without adhesion.

• Yolk Sack:– Provides initial nutrients, supplies earliest

RBCs and seeds the gonads with primordial llgerm cells.

Fetal MembranesFetal MembranesFetal MembranesFetal Membranes

C ll dC ll d hh BB ff WWCalledCalled thethe BagBag ofof WatersWaters

ConsistsConsists ofof twotwo layerslayers

11)) AmnionAmnion-- innerinner membrane,membrane, nextnext toto fetusfetus

22)) ChorionChorion-- outerouter membrane,membrane, nextnext toto mothermother

FunctionFunction:: toto househouse thethe fetusfetus forfor thethe durationduration ofofpregnancy,pregnancy, protectsprotects fromfrom outsideoutside world,world, preventspreventsp g y,p g y, pp ,, pp

verticalvertical transmissiontransmission ofof infectioninfection..

Properties of Amniotic FluidAmniotic fluid is the fluid medium that the fetus is surrounded within the amniotic

itcavity.

The volume ranges from 400-1,200 ml, g , ,depending on the week of pregnancy.

Mainly composed of waterMainly composed of water.

Also composed of ions including sodium, hl i d l ichlorine, and calcium.

Amniotic fluid contains urea, which comes ,from the fetus.

Variations Of Substances In Amniotic Fluid

1200

1000

% o

r

Hemoglobin(%)

Iron (mg/100ml)

600

800

bsta

nce

(%00

ml) Cholesterol

(mg/100ml)

Lipids

400

unt o

f sub

mg/

10 Lipids(mg/100ml)

200Amo

02 3 4 5 6 7 8 9Months of Pregnancy

Amniotic Fluid Volume Versus Gestation Period In WeeksGestation Period In Weeks

1. Amniotic fluid ⇑rapidly from anrapidly from an average vol. of 50ml by 12 weeks of pregnancy to 400ml t idat mid-pregnancy.

2. The 24th week of th lpregnancy, the vol.

of amniotic fluid continues to ⇑

3. Maximum of about 1 liter of fluid at 36 to 38 k38 weeks.

Umbilical Cord

• The lifeline between mother and fetus• Origin : It develops from the connecting stalk• 50 cm, diameter 2 cm ,• Contains 3 vessels: 2 arteries and 1 vein, • If abnormal of vessels present- often p

associated with fetal anomalies (heart and kidneys).

• The arteries carry “dirty blood” away from fetus. The vein carries “clean” blood to fetus.C t l i ti i t th l t i l• Central insertion into the placenta is normal

Umbilical • Contents

– 2 arteries that carry blood to the placenta1 umbilical vein that carries oxygenated blood to the fetus

Cord– 1 umbilical vein that carries oxygenated blood to the fetus– primitive connective tissue

• Stub drops off in 2 weeks leaving scar (umbilicus)Stub drops off in 2 weeks leaving scar (umbilicus)

The PlacentaThe PlacentaThe PlacentaThe Placenta

Th Pl tTh Pl tThe PlacentaThe Placenta

The placenta consists of thousands of tiny The placenta consists of thousands of tiny

branched fingers of tissue calledbranched fingers of tissue called CHORIONICCHORIONICbranched fingers of tissue called branched fingers of tissue called CHORIONIC CHORIONIC

VILLIVILLI these project into the endometrium. these project into the endometrium.

The maternal blood vessels surrounding the The maternal blood vessels surrounding the

chorionic villi break down forming maternalchorionic villi break down forming maternalchorionic villi break down forming maternal chorionic villi break down forming maternal

blood sinusesblood sinuses

Origin:Origin:The placenta develops from The placenta develops from

gg

the the chorion frondosumchorion frondosum( foetal origin)( foetal origin)( foetal origin) ( foetal origin) and and decidua basalisdecidua basalis( maternal origin)( maternal origin)( maternal origin).( maternal origin).

Anatomy At TermAnatomy At TermyyShapeShape :: discoiddiscoidShape Shape : : discoid. discoid. DiameterDiameter : : 1515--20 cm.20 cm.W i htW i ht 500500WeightWeight : : 500 gm.500 gm.ThicknessThickness: : 2.5 cm at its center and gradually 2.5 cm at its center and gradually

tapers towards the periphery.tapers towards the periphery.Position Position : : in the upper uterine segment in the upper uterine segment pp gpp g

(99.5%),(99.5%), either in the posterior surface either in the posterior surface (2/3)(2/3)or the anterior surface or the anterior surface (1/3).(1/3).( )( )

Maternal side of placenta

Fetal Side of placenta

a. Foetal surfacea. Foetal surface•• Smooth, glisteningSmooth, glistening and is covered by theand is covered by the amnionamnion

which is reflected on the cord which is reflected on the cord which is reflected on the cord. which is reflected on the cord. •• The The umbilical cordumbilical cord is inserted near or at the center is inserted near or at the center

of this surface and its radiating branches can be of this surface and its radiating branches can be ggseen beneath the amnion.seen beneath the amnion.

b.b. MaternalMaternal surfacesurfaceD ll i h d i l d i di id d i t 15 20 • Dull greyish red in colour and is divided into 15-20 cotyledons.

• Each cotyledon is formed of the branches of one • Each cotyledon is formed of the branches of one main villus stem covered by decidua basalis.

Placental Function

O2Glucose VitaminsMinerals

Functions Of The PlacentaFunctions Of The Placenta(1)(1) RRespiratory functionespiratory function(2)(2) NNutritive functionutritive function(3)(3) EExcretory functionxcretory function(3)(3) EExcretory functionxcretory function(4)(4) PProduction of enzymesroduction of enzymes(5)(5) PProduction of pregnancy associated plasma roduction of pregnancy associated plasma

proteins (PAPP)proteins (PAPP)proteins (PAPP)proteins (PAPP)(6)(6) BBarrier functionarrier function(7)(7) EEndocrine functionndocrine function

Th Pl tThe PlacentaT bl h i h f t i l thTable showing exchange of materials across the

placentaMother to Foetus Foetus to MotherMother to Foetus Foetus to Mother

• Oxygen yg• Glucose • Amino acids • Lipids, fatty acids & glycerol • Carbon dioxide • Vitamins • Ions : Na, Cl, Ca, Fe • Alcohol, nicotine + other drugs • Viruses

• Urea • Other waste products

• Viruses • Antibodies

(1) Respiratory function:(1) Respiratory function:

•• O2O2 andand CO2CO2 pass across the placenta bypass across the placenta by simplesimpleO2 O2 and and CO2CO2 pass across the placenta by pass across the placenta by simple simple diffusiondiffusion. .

•• The The foetal haemoglobinfoetal haemoglobin has more affinityhas more affinitygg yyand carrying capacity than adult haemoglobin. and carrying capacity than adult haemoglobin.

•• 2,3 diphosphoglycerate2,3 diphosphoglycerate (2,3(2,3--DPG) which competesDPG) which competes2,3 diphosphoglycerate2,3 diphosphoglycerate (2,3(2,3 DPG) which competes DPG) which competes for oxygen binding sites in the haemoglobin for oxygen binding sites in the haemoglobin molecule, is less bounded to the foetal molecule, is less bounded to the foetal haemoglobin haemoglobin (HbF)(HbF) and thereby allows a greater and thereby allows a greater uptake of O2 uptake of O2 ( O2 affinity).( O2 affinity).

(1) Respiratory function(1) Respiratory function

The rate of diffusion depends upon:The rate of diffusion depends upon:11 MM t l/ f t l di tt l/ f t l di t1.1. MMaternal/ foetal gases gradient.aternal/ foetal gases gradient.2.2. MMaternal and foetal placental blood flow.aternal and foetal placental blood flow.3.3. PPlacental permeability.lacental permeability.4.4. PPlacental surface area.lacental surface area.4.4. PPlacental surface area.lacental surface area.

Th t f f t i t f th th t th f t iTh t f f t i t f th th t th f t i

((22) Nutritive function) Nutritive functionThe transfer of nutrients from the mother to the foetus is The transfer of nutrients from the mother to the foetus is

achieved by :achieved by :11 SSimple diffusionimple diffusion : e g water and electrolytes: e g water and electrolytes1.1. SSimple diffusionimple diffusion : e.g. water and electrolytes.: e.g. water and electrolytes.2.2. FFacilitated diffusionacilitated diffusion: e.g. glucose.: e.g. glucose.33 AActive diffusionctive diffusion: e g amino acids: e g amino acids3.3. AActive diffusionctive diffusion: e.g. amino acids.: e.g. amino acids.4.4. PPinocytosisinocytosis: e.g. large protein molecules and cells.: e.g. large protein molecules and cells.

(3) Excretory function(3) Excretory functionWaste products of the foetus as Waste products of the foetus as ureaurea are passesare passesto maternal blood by to maternal blood by simple diffusionsimple diffusion through thethrough theplacenta.placenta.

((4) Production of enzymes:4) Production of enzymes:•• e g :e g :•• e.g.:e.g.:•• Oxytocinase, Oxytocinase, •• Monoamino oxidase, Monoamino oxidase, ,,•• Insulinase, Insulinase, •• Histaminase Histaminase and and •• Heat stable alkaline phosphatase.Heat stable alkaline phosphatase.

(5) Production of pregnancy associated plasma proteins (PAPP)(5) Production of pregnancy associated plasma proteins (PAPP)(5) Production of pregnancy associated plasma proteins (PAPP)(5) Production of pregnancy associated plasma proteins (PAPP)

PAPPPAPP AA•• PAPPPAPP--A, A, •• PAPPPAPP--BBPAPPPAPP--A, A, PAPPPAPP--B, B, PAPPPAPP--C, C, PAPPPAPP D andD and

•• PAPPPAPP--B, B, •• PAPPPAPP--C, C, •• PAPPPAPP--D D andandPAPPPAPP--D andD andPP5. PP5. The exact function of these proteins is not defined.The exact function of these proteins is not defined.

•• PP5. PP5. •• The exact function of these proteins is not defined.The exact function of these proteins is not defined.

(6) Barrier function:(6) Barrier function:The foetal blood in the chorionic villi is separated from

the maternal blood, in the intervillous spaces, by the Placental BarrierPlacental Barrier which is composed of :which is composed of :

1. Endothelium of the foetal blood vessels,2. The villous stroma,3. The cytotrophoblast, and4. The syncytiotrophoblast.y y p

(6) Barrier function:(6) Barrier function:

However, it However, it is an incomplete barrier.,, p•• IIt allows the passage of t allows the passage of antibodies (IgG only), antibodies (IgG only),

hormones, antibiotics, sedatives, some viruseshormones, antibiotics, sedatives, some viruses as as rubella and smallpox and rubella and smallpox and some organismssome organisms as as treponema pallida.treponema pallida.

•• SSubstances of ubstances of large molecular sizelarge molecular size as heparin and as heparin and insulin cannot pass the placental barrier.insulin cannot pass the placental barrier.

(7) Endocrine function(7) Endocrine function

(A) Protein hormones:(A) Protein hormones:( )( )11-- Human chorionic gonadotrophin Human chorionic gonadotrophin (hCG)(hCG)22-- Human placental lactogenHuman placental lactogen (hPL)(hPL)22 Human placental lactogen Human placental lactogen (hPL)(hPL)33-- Human chorionic thyrotrophin Human chorionic thyrotrophin (hCT)(hCT)44-- Hypothalamic and pituitary like hormonesHypothalamic and pituitary like hormones44 Hypothalamic and pituitary like hormonesHypothalamic and pituitary like hormones55-- Others as inhibin, relaxin and beta endorphins.Others as inhibin, relaxin and beta endorphins.(B) Steroid Hormones:(B) Steroid Hormones:(B) Steroid Hormones:(B) Steroid Hormones:11-- OestrogensOestrogens22 ProgesteroneProgesterone22-- ProgesteroneProgesterone

Hormonal Secretion by the Placenta

HCGHCGIt is a glycoprotein produced by the syncytiotrophoblast.It is a glycoprotein produced by the syncytiotrophoblast.g y p p y y y pg y p p y y y p-- It supports the corpus luteum in the first It supports the corpus luteum in the first 10 10 weeks of pregnancy weeks of pregnancy

to produce oestrogen and progesterone until the to produce oestrogen and progesterone until the ti t h bl t d tti t h bl t d tsyncytiotrophoblast can produce progesterone.syncytiotrophoblast can produce progesterone.

HCG molecule is composed of HCG molecule is composed of 2 2 subunitssubunits::HCG molecule is composed of HCG molecule is composed of 2 2 subunitssubunits::a.a. AlphaAlpha subunit:subunit:

which is similar to that of FSH, LH and TSH.which is similar to that of FSH, LH and TSH.,,b.b. BetaBeta subunit:subunit:

which is specific to hCG.which is specific to hCG.

•• HCG rises sharply after implantation, reaches a peak of HCG rises sharply after implantation, reaches a peak of 100.000 mIU/ml about the 60 th day of pregnancy 100.000 mIU/ml about the 60 th day of pregnancy 100.000 mIU/ml about the 60 th day of pregnancy 100.000 mIU/ml about the 60 th day of pregnancy

•• then falls sharply by the day 100 to 30.000 mIU/ml and is then falls sharply by the day 100 to 30.000 mIU/ml and is maintained at this level until term.maintained at this level until term.

Estimation of betaEstimation of beta--hCG is used for:hCG is used for:Estimation of betaEstimation of beta hCG is used for:hCG is used for:a) Diagnosis of a) Diagnosis of earlyearly pregnancy.pregnancy.b) Diagnosis of b) Diagnosis of ectopicectopic pregnancypregnancyb) Diagnosis of b) Diagnosis of ectopicectopic pregnancy.pregnancy.c) Diagnosis and c) Diagnosis and followfollow--upup of trophoblastic disease.of trophoblastic disease.

Hormone BloodBlood Levels

• Human chorionic gonadotropingonadotropin (hCG) produced by the chorion is less important after 4 months, because the placenta takesthe placenta takes over the hormonal secretion of the corpus luteum.

Placental Lactogen (hPL) or hCSStructurally similar to prolactin and GH (produced bytrophoblast cells)Promotes glandular breast development (LITTLEPromotes glandular breast development (LITTLEeffect on milk production though)Increases fat mobilization (like GH), and decreasesIncreases fat mobilization (like GH), and decreasesmaternal glucose utilization, thereby increasing energystores (glucose and AA’s) for the fetus.Mom, thus, relies on fatty acids and Triglycerides whiletransferring AA’s and glucose to fetus (via thishormone).hormone).Implicated in gestational diabetes in 4% ofpregnancies. (how to avoid mom’s glucose utilization?Well, insulin resistance could do that…but what ifinsulin resistance in the mom goes out of control???)

RelaxinSecreted by the corpus luteum and then the placenta

Levels rise late in pregnancyp g y

Loosens connective tissue

Widens pubic symphysis so head can pass throughp y p y p g

Inhibits spontaneous uterine contractions

Promotes cervical effacement

Flattening, spreading, dilation of cervical os

inhibits secretion of FSH and might regulate secretion of hGH.g g

produced by the ovaries, testes, and placenta

Corticotropin releasing hormone (CRH)Corticotropin-releasing hormone (CRH)

increases secretion of fetal cortisol (lung maturation)thought to be the “clock” that establishes the timing ofthought to be the clock that establishes the timing of birth.

Endocrinology of pregnancyProgesterone

Maternal blood supplies cholesterolPl t t h l t l t tPlacenta converts cholesterol to progesterone

Takes over following luteolysisProduces enough to support pregnancy by 5-6 wks in humans

Necessary for endometrial support and secretion∴ necessary for support of pregnancy

“pro” = support ... “gest” = gestation = pregnancyExerts negative feedback on LH and FSH

Ovarian follicles do not growNo stimulation for ovarian steroid production

Increases fat depositionStimulating appetiteDiverting energy stores from sugar to fate t g e e gy sto es o suga to at

Endocrinology of pregnancyFeto-Placental Unit - Estrogens

Progesterone from placenta to fetal adrenal glandThrough umbilical and fetal vasculature

Outer layers (cortex)fetal adrenal zone converts P to DHEA (dehydroepiandrosterone)fetal adrenal zone converts P to DHEA (dehydroepiandrosterone)

DHEA circulates to fetal liver → converted to 16α-OH-DHEA sulfateConverted to estriol in the placenta

E3 is the primary estrogen during pregnancyF t d l t t t d t lFetus and placenta cooperate to produce maternal estrogens

EFFECTS OF PREGNANCY ON THE MOTHER• Anatomical Changes:

– The female reproductive organs and breasts become increasingly vascular and engorged with blood

– The uterus enlarges dramatically, causing a shift in the woman’s center of gravity and an accentuated lumbarwoman s center of gravity and an accentuated lumbar curvature (lordosis)

– Placental production of the hormone relaxin causes pelvic ligaments and the pubic symphysis to soften and relax

• This increases motility for easier birth passage• This increases motility for easier birth passage– There is a normal weight gain of around 28 pounds,

due to growth of the fetus, maternal reproductive organs, and breasts, and increased blood volume

EFFECTS OF PREGNANCY ON THE MOTHERTHE MOTHER

• Good nutrition is necessary all throughGood nutrition is necessary all through pregnancy if the developing fetus is to have all the building materials (especially proteins, calcium, and iron) needed to form its tissues

• Multivitamins containing folic acid seem to reduce the risk of having babies with neurological problems, including such birth defects as spina bifida and anencephalydefects as spina bifida and anencephaly (absence of brain and cranial vault with cerebral hemisphere missing or reduced in size)hemisphere missing or reduced in size)

RELATIVE SIZE OF THE UTERUS BEFORE CONCEPTION AND DURING PREGNANCYCONCEPTION AND DURING PREGNANCY

Ph i l i l ChPhysiological Changes

Cardiovascular Digestive

Respiratory

Urinary

Skin

BreastsUrinary

Metabolic

Breasts

BiomechanicalMetabolic

Thermoregulation

Biomechanical

Cardiovascular ChangesCardiovascular ChangesDECREASEDECREASEINCREASEINCREASE

• Blood volume

• Cardiac (heart)

• Hematocrit

• Blood pressure ( )output

• Stroke volume

p

• Blood supply to uterus

C diStroke volume

• End diastolic volume

• Cardiac reserve

• Vascular resistance volume

• Resting pulse HYPERTENSION ????HYPERTENSION ????

• % of blood plasmaHYPERTENSION ????HYPERTENSION ????

Blood Flow Through the Placenta, andg ,Cardiac Output During Pregnancy.

About 625 milliliters of blood flows through the maternalcirculation of the placenta each minute during the lastmonth of pregnancy. This, plus the general increase inthe mother’s metabolism, increases the mother’scardiac output to 30 to 40 per cent above normal by the27th week of pregnancy; then, for reasons unexplained,the cardiac output falls to only a little above normalduring the last 8 weeks of pregnancy, despite the highuterine blood flow.

The maternal blood volume shortly before term is about 30

Blood Volume During PregnancyThe maternal blood volume shortly before term is about 30per cent above normal.This increase occurs mainly during the latter half ofy gpregnancy. The cause of the increased volume is likelydue, at least in part, to aldosterone and estrogens, which

tl i d i d t i d fl idare greatly increased in pregnancy, and to increased fluidretention by the kidneys.Also, the bone marrow becomes increasingly active andAlso, the bone marrow becomes increasingly active andproduces extra red blood cells to go with the excess fluidvolume. Therefore, at the time of birth of the baby, themother has about 1 to 2 liters of extra blood in hercirculatory system.

Physiologic anemia of pregnancyPhysiologic anemia of pregnancy

• Physiologic intravascular changey g g• Plasma volume increases 50-70 %

– Beginning by the 6th wkg g y• RBC mass increases 20-35 %

– Beginning by the 12th wk• Disproportionate increase in plasma volume

over RBC volume----HemodilutionD i h d i h i• Despite erythrocyte production there is a physiologic fall in the hemoglobin and hematocrit readingsreadings

Maternal changes - anatomical and physiological continued

• Pulmonary changes:– increase in tidal volume– decrease in ERV

i i i t l f til ti– increase in minute volume of ventilation– decrease in airway resistance– increase in oxygen uptake at given workincrease in oxygen uptake at given work

load– Dyspnea (difficulty breathing)

Maternal Respiration During PregnancyBasal metabolic rate + her greater size the total amount of oxygenused by the mother shortly before birth of the baby is about 20 % abovenormal and a commensurate amount of carbon dioxide is formed Thesenormal, and a commensurate amount of carbon dioxide is formed. Theseeffects cause the mother’s minute ventilation to increase.

Levels of progesterone increase the minute ventilation even more.p g(progesterone increases the respiratory center’s sensitivity to carbondioxide.)The net result is an increase in minute ventilation of about 50% and aThe net result is an increase in minute ventilation of about 50% and adecrease in arterial PCO2 to several millimeters of mercury below that in anonpregnant woman.Simultaneously, the growing uterus presses upward against the abdominalcontents, and these press upward against the diaphragm, so that the totalexcursion of the diaphragm is decreased.p gConsequently, the respiratory rate is increased to maintain the extraventilation.

Function of the Maternal Urinary System During Pregnancy

The rate of urine formation is usually slightly increased because of

increased fluid intake and increased load or excretory products. But in

• First, the renal tubules’ reabsorptive capacity for sodium, chloride,

addition, several special alterations of urinary function occur.

and water is increased as much as 50 per cent as a

consequence of increased production of steroid hormones by the

placenta and adrenal cortex.

• Second, the glomerular filtration rate increases as much as 50

per cent during pregnancy which tends to increase the rate ofper cent during pregnancy, which tends to increase the rate of

water and electrolyte excretion in the urine. When all these

effects are considered the normal pregnant woman ordinarilyeffects are considered, the normal pregnant woman ordinarily

accumulates only about 6 pounds of extra water and salt.

Metabolism During PregnancyAs a consequence of the increased secretion of many

Metabolism During Pregnancy

hormones during pregnancy, including thyroxine,adrenocortical hormones, and the sex hormones, the basalmetabolic rate of the pregnant woman increases about 15 percent during the latter half of pregnancy.As a result, she frequently has sensations of becomingoverheated. Also, owing to the extra load that she is carrying,

t t f th l t b d d fgreater amounts of energy than normal must be expended formuscle activity.

Adaptations for ProtectionAdaptations for Protection

• Core temperature fallsCore temperature falls

• Perspire more rapidly

• Greater skin area and increased blood vessels allow added evaporationvessels allow added evaporation

• Increased ventilation promotes cooling

• Enhanced regulation of internal temperature in consistent exerciserp

WATER WATER WATERWATER, WATER, WATERHydration is a major concern Hydration is a major concern

during maternal exerciseduring maternal exercise• Provide a ready source of water

during maternal exercise.during maternal exercise.

• Encourage frequent water breaks

EFFECTS OF PREGNANCY ON THE MOTHERC S O G C O O

• Metabolic Changes:As the placenta enlarges it produces human placental– As the placenta enlarges, it produces human placental lactogen, which works with estrogen and progesterone to promote maturation of the breasts for lactation

– Human placental lactogen (hPL) also promotes the growth of the fetus, and exerts a glucose-sparing effect on maternal metabolismmetabolism

• Consequently, maternal cells metabolize more fatty acids and less glucose than usual, sparing glucose for use by the g , p g g yfetus

– Human chorionic thyrotropin from the placenta increases maternal metabolic rate

Metabolic ChangesMetabolic Changes

INCREASES IN:INCREASES IN:• Insulin level • Carbohydrate utilization during exercise as

INCREASES IN:INCREASES IN:

Carbohydrate utilization during exercise as weight increases

• EstrogenEstrogen • Progesterone • Relaxin• Relaxin• Caloric requirements by ~ 300 calories/day• Protein and fluid requirements• Protein and fluid requirements

Digestive ChangesDigestive Changes• Digestive system slows g y• Intestines are pushed up and to the

sides • Smooth muscle of the stomach relaxes• Smooth muscle of the stomach relaxes

and can cause heartburn

Constipation and hemorrhoids are commonConstipation and hemorrhoids are commonConstipation and hemorrhoids are common Constipation and hemorrhoids are common during pregnancyduring pregnancyMorning sicknessMorning sicknessMorning sicknessMorning sickness

Urinary ChangesUrinary Changes

• Kidneys grow and filter moreKidneys grow and filter more blood as the blood volume increases

• Become more susceptible to bl dd d kid i f tibladder and kidney infections

• Bladder becomes compressedBladder becomes compressed causing frequent urination and incontinence

Skin ChangesSkin Changes

• Stretch marksStretch marks• Dark pigmented line on there abdomen

which is called Linea Nigrawhich is called Linea Nigra• Pigment changes on their face and neck• Small blood vessels in the face, neck and

upper chest pp• MOST OF THESE RESOLVE AFTER

PREGNANCYPREGNANCY

Breast ChangesBreast ChangesEarly in pregnancy, Early in pregnancy, y p g y,y p g y,tenderness and tightness tenderness and tightness is commonis common

After 8 weeks, breasts After 8 weeks, breasts grow and blood vesselsgrow and blood vessels

Ni l b l d d k

grow and blood vessels grow and blood vessels often are visibleoften are visible

• Nipples become larger and darker

• A thick yellowish fluid can be expressed y pfrom the nipple

Biomechanical Changesg

• Weight distribution shiftsWeight distribution shifts

• Joint movement

• Balance of muscle strength

• Spinal curves increasep

• Joint laxity becomes greater

M t t l di f t• More structural discomfort

• Increased potential for nerve compression

Changes to Body System• First Trimester

– Baby begins to grow• Third Trimester

– Baby has more rapidy g g– Increased urination– Changes with skin and hair

Thi k i i tli

– Baby has more rapid growth & weight gain

– Backaches– Thickening waistline– Nausea/fatigue

• Second Trimester

– Swelling of the hands, legs, and feet• Second Trimester

– Baby’s weight increases– Energy level improves

– Breathlessness– More frequent

– Heartburn– Leg cramps

Pel is rela es ca sing SI

urination

– Pelvis relaxes causing SI discomfort