Physiologi of Labor

7/24/2019 Physiologi of Labor

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PHYSIOLOGY OFLABOR

RIBKHI AMALIA PUTRI

GANOT SUMULYO


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PREFACE

Extensive preparationsin bothuterus and cervix long before lastfew hours of pregnancy

Transitional phase myometrialunresponsiveness is suspended, and

the cervix undergoes ripening,eacement, and lost of structuralintegrity

Laor onset !"l#ination o$series o$ io!he#i!al !han%es inthe "ter"s an& !er'i(as theresult of endocrine and paracrinesignals emanating from both motherand fetus

Anor#al part"rition pretermlabor, dystocia, postterm pregnancy

Fetus

MotherPlacenta

Membranes


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PHASE OF

PARTURITION


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Uterine Activity During Pregnancy

2

/23/

16

4

InhibitorsProgesteroneProstacyclineRelaxinNitric Oxide

Paratyroidor!one"related

#e#tide $R% %P&

Quiescence

UterotoninsProstaglandins

Oxytocin

Stimulation

Uterotrophins'strogenProgesteroneProstaglandins$R%

Activation

InvolutionOxytocin(ro!)in

Involution


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M)o#etrial A!tion

Contractiongreaterdegree smooth muscle cellshortening

Multiple directions

Not organied as s!eletalmuscle


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Re%"lation o$ M)o#etrial

Contra!tion an& Rela(ation

"ctin#Myosin $nteraction activates "%Pase, hydrolyes"&P, generate force

$ntracellular Calcium P'F(a and oxytocin receptors

Myometrial gap )unctions

Cell *urface +eceptors


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A!tin M)osin


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A!tin M)osin


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2

/23/

16

*

$alciu! cannel

Castore

+ Oxytocin

+ Prostaglandin

$a+ ,&$-

'xtracellular

.ntracellular

Uterine contractions

cAMP

Oxytocin rece#tor

Pos#oli#ase $

Intra!ell"lar Cal!i"#


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terusconnexins (-,./, .0, .1

C+2+3a and 42 receptors

Gap *"n!tion Cell S"r$a!eRe!eptors


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Phase + o$ Part"rition,

Uterine -"ies!en!e an&Cer'i!al So$tenin%


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Uterine -"ies!en!e

5eginning even before implantation terine smooth muscle tran6uility

terus unresponsive until near the end of pregnancy terus initiate sie and vascularity extension to

accommodate pregnancy Braxton Hicks or false labor


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Cer'i!al So$tenin%

First palpable softening of lower uterine segment at .#-wgapregnancy diagnosis 2egar sign

Cervix7s function during pregnancy8

39 5arrier

protect from infection(9 Cervical competence despite increasing gravitationalforces

09 Extracellular matrix changes that allow progressiveincreases in tissue compliance

/ *tructural changes8. $ncreased vascularity, stromal hypertrophy, glandular

hypertrophy and hyperplasia, and slow, progressivecompositional or structural changes of extracellular matrix


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Pro%esterone

promote expression of inhibitorytranscription factor :E53;inc, recruitcoregulatory factors8 P*F;polypyrimidine tract bindingprotein#associated splicing factor

and *in0"?2&"Cs;yeast switch#dependent0 homologue"?histone deacetylasecorepressor complexinhibit expression of the

C"P genes, connexin .0,and oxytocin receptor

inhibit expression of thegene encoding the gap)unctional proteinconnexin .0


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L"teini.in% Hor#one/LH0 an& H"#an

Chorioni!Gona&otropin /hCG0Re!eptors

activate adenylyl cyclase byway of a plasma membranereceptor@'As#lin!ed

decreases contractionfre6uency and force

decreases the number oftissue#speci


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Atrial an& BrainNatri"reti! Pepti&es

an& C)!li! G"anosineMonophosphate/!GMP0

"ctivation of guanylylcyclase increasesintracellular c'MP levels

promotes smooth musclerelaxation

Beta1A&renore!eptors

c"MP signaling

promotes smooth musclerelaxation


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Phase 2 o$ Part"rition,

Preparation $or Laor


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Uterine Chan%es

terine awa!ening or activation

Progression of uterine changes during -#B wga

$ncrease of contracted-associated protein (CAPs) oxytocinreceptor, P'F receptor, and connexin .0 increase uterine

irritability and responsiveness to uterotonins

Formation of lower uterine segment from the isthmus fetal head often descends to or even though the pelvic inlet9


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Cer'i!al Chan%es

Cervical ripening

%ransition from the softening to ripening, begins wee!sor days before onset of contraction

%otal amount and composition of proteoglycans andglycosaminoglycans within the matrix are altered

*tromal invasion with inammatory cells ervicalchemottractants attract inammatory cells releaseprotease degradation of collagen and other matrix

component


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Fibril sie and pac!ing are regulated by small protegoglycan such asdecorin that bind collagen95efore cervical ripening,


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Hor#onal Chan%es

Progesteron withdrawl

Dxcytosin activation increased phospholipase C activity andsubse6uent increases in cytosolic calcium levels and

uterine contractility


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Laor


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Phase 3, Uterine Sti#"lation

+eceptors stri!ingly increases in myometrial and decidualtissues near the end of gestation

"cts on decidual tissue to promote prostaglandin release *ynthesied directly in decidual and extraembryonic fetal

tissues and in the placenta

O()to!in

levels of prostaglandins;or their metabolites;in amnionic uid,maternal plasma, and maternal urine are increased during labor

the receptor level for P'F(A is increased in the decidua at term,and this increase most

%he fetal membranes and placenta also produce prostaglandins9Primarily P'E(, but also P'F(A,

Prosta%lan&in


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*ynthesied in the placenta and hypothalamus9 C+2 plasma levels increase dramatically during the


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"ngiotensin $$ binding to the plasma#membranereceptor evo!es contraction

%wo '#protein#lin!ed angiotensin $$ receptors expressed

in the uterus;"%3 and "%(9 $n nonpregnant women,the "%( receptor is predominant, but the "%3 receptoris preferentially expressed in pregnant women

An%iotensin II


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Sta%es o$Laor

&ivided into threestages8

First stage @ onset

of labor tocomplete dilatation

4atent phase

"ctive phase

*econd stage

fetal expulsion %hird stage

placentalseparation andexpulsion


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First Sta%e o$ Laor,Clini!al Onset o$ Laor

Forceful uterine contractions that eect deliverybegin suddenly

4abor initiation spontaneous release of a

small oc blood#tinged mucus from the vagina Hbloody showI


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Uterine Laor Contra!tion

$nterval gradually diminished from approximately 3/ minutesat onset of

Pain of contraction8

2ypoxia of the contracted myometrium Compression of nerve ganglia in the cervix and lower uterusby contracted interloc!ing muscle bundles

Cervical stretching during dilatation *tretching of the peritoneum overlying the fundus


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4istin!t o$ Upper an&Lo5er Uterine Se%#ent

pper segment8 Firm Contracts, retracts, and expels the

fetus Myometrium dosen7t relax to

original length after contraction diminished content, but constanttension

terine cavity become slightlysmaller with each contraction

progressively thic!ened4ower segment8 *ofter, distended, more passive *oftened and dilated greatly

expanded, thinned#out the tube fetus can be pass


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4istin!t o$ Upper an&Lo5er Uterine Se%#ent


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Centrifugaal pull is exerted onthe cervix and createscervical dilatation

Pressure to the membrane hydrostatic action of amnionsac dilates the cervicalcanal


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Changes in terus *hape &uring 4abor elongationof the ovoid uterine shape and decrease horiontaldiameter increase fetal axis pressure, straighten

fetal vertebral column

"ncillary Forces in labor maternal intraabdominalpressure as pushing


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Cer'i!al Chan%es

Eacement and

dilatation occur inthe already#ripenedcervix

Eacament shortening of

cervical canal ( cmto circular ori


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Se!on& Sta%e o$ Laor, Fetal4es!ent


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Car&inal Mo'e#ents o$ Laor

Engangement

&escent

Flexion

$nternal rotation Extension

External rotation

Expulsion

2/

23/

16

42


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Thir& Sta%e o$ Laor, 4eli'er) o$Pla!enta an& Me#ranes

Contraction of uterus diminishing sie decreasearea of placental implantation site

$ncreased placental thic!ness and limited elasticitytension pulls the wea!est layer =decidua>

Membranes are peeled o the uterine wall byfurther contraction of myometrium and traction


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The P"erperi"#


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Myometrium in state rigid and persistent contractionand retraction

&irectly compresses large uterine vessels and allows

thrombosis prevent hemorrhage Dnset of lactogenesis

+einstitution of ovulation signal .#- wee!s afterbirth


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Fetal Contri"tions


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From the fetal hypothalamic#pituitary#adrenal axis

Fetal En&o!rine Cas!a&es Lea&in% toPart"rition

*ynthesied in large amount *timulate by cortisol Placental C+2 may enhance fetal cortisol production to

provide positive feedbac! so that the placenta

produces more C+2 *timulate fetal adrenal C3K#steroid synthesis, therebyincreasing substrate for placental aromatiation shiftthe expression of a series of myometrial contractileproteins

Pla!ental Corti!otropin1Releasin% Hor#one

Pro&"!tion


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*urfactant protein " =*P#"> produced by the fetal lung isre6uired for lung maturation $ncreased in amnionic uid at term activate uid

macrophages to migrate into the myometrium andinduce NF#L5

Fetal L"n%S"r$a!tant

fetal anencephaly fetal brain#pituitary#adrenal

function adrenal hypoplasia

Fetal Ano#alies an& 4ela)e&Part"rition


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Intra"terine Tiss"es

Contri"tions


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%ensile strength;resistance to tearing and rupture;ofthe fetal membranes

*everal bioactive peptides and prostaglandins that causemyometrial relaxation or contraction are synthesied inamnion

A#nion

Enymes include prostaglandin dehydrogenase =P'&2>,

oxytocinase, and en!ephalinase

Chorion Lae'e


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&ecidual uterotonins that act in a paracrine on contiguousmyometrium

Expresses steroid metaboliing enymes such as (/A#2*& andsteroid 1A+3 that may regulate local progesterone withdrawal

&ecidual activation is characteried by increasedproinammatory cells and increased expression ofproinammatory cyto!ines, prostaglandins, and uterotoninssuch as oxytocin receptors and connexin .0

Cyto!ines produced in the decidua can either increaseuterotonin production

4e!i&"a


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Re$eren!es

illiam Dbstetric (.thEdition

Creasy +esni!7s Maternal#Fetal Medicine

*teven 'abbe, Dbstetric Normal and Problem

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Physiologi of Labor