ch 12. mechanisms of normal labor 부산백병원 산부인과 r1 서 영 진

Ch 12. Mechanisms of Ch 12. Mechanisms of normal normal laborlabor

부산백병원 산부인과 부산백병원 산부인과 R1 R1 서 영 진서 영 진

LIE, PRESENTATION,LIE, PRESENTATION, ATTITUDE, AND ATTITUDE, AND POSITIONPOSITION

By abdominal palpation, vaginal examination, aBy abdominal palpation, vaginal examination, and auscultation, or by technical means (USG, X-nd auscultation, or by technical means (USG, X-ray)ray)

Fetal lieFetal lie -the relation of the long axis of the fetus to-the relation of the long axis of the fetus to that of the motherthat of the mother -longitudinal (99% at term)-longitudinal (99% at term) transverse : multipara, pl reviatransverse : multipara, pl revia hydramnios, Ut anomalieshydramnios, Ut anomalies oblique: unstable (become logitudinal or oblique: unstable (become logitudinal or transv.)transv.)


Fetal presentationFetal presentation -the foremost portion of the body of the fetus-the foremost portion of the body of the fetus within the birth canalwithin the birth canal -can be felt through the cevix on vaginal exam.-can be felt through the cevix on vaginal exam. -longitudinal lie: head (cephalic presentation)-longitudinal lie: head (cephalic presentation) breech (breech presentation)breech (breech presentation) transverse lie: shouldertransverse lie: shoulder


# Cephalic presentation# Cephalic presentation -Ordinarily, the head is flexed sharply so that-Ordinarily, the head is flexed sharply so that the chin is in contact with the thoraxthe chin is in contact with the thorax -the occipital fontanel is the presenting part-the occipital fontanel is the presenting part -referred to as a vertex or occipital presentation-referred to as a vertex or occipital presentation -extended so that the occiput is in contact with the -extended so that the occiput is in contact with the back : face back : face sinciput (ant. fontanel or bregma)sinciput (ant. fontanel or bregma) browbrow -sinciput, brow: transient -> vertex or blow -sinciput, brow: transient -> vertex or blow


# Breech presentation# Breech presentation

-frank: the thighs are flexed and the legs extended-frank: the thighs are flexed and the legs extended

over the anterior surface of the bodyover the anterior surface of the body

complete: the thighs are flexed on the abdomencomplete: the thighs are flexed on the abdomen

and the legs upon the thighsand the legs upon the thighs

incomplete: the lowermost part is one or both feet,incomplete: the lowermost part is one or both feet,

or one or both knees (footling)or one or both knees (footling)


Fetal attitude or postureFetal attitude or posture -the fetus forms an ovoid mass that corresponds-the fetus forms an ovoid mass that corresponds roughly to the shape of the uterine cavityroughly to the shape of the uterine cavity -back: markedly convex-back: markedly convex head: flexed (chin-chest)head: flexed (chin-chest) thighs: flexed over the abdomenthighs: flexed over the abdomen legs: bent at the kneelegs: bent at the knee feet: flexed (ant. surfaces of the legs) at the anklefeet: flexed (ant. surfaces of the legs) at the ankle arms: crossed or parallel over the thoraxarms: crossed or parallel over the thorax -face presentaton: concave (extended) of the-face presentaton: concave (extended) of the vertabral column vertabral column


Fetal positionFetal position - the relation of arbitrarily chosen portion of the- the relation of arbitrarily chosen portion of the fetal presenting part to the right or left side offetal presenting part to the right or left side of the maternal birth canalthe maternal birth canal

- Rght vs. Left- Rght vs. Left

-vertex: occiput-vertex: occiput face: chin (mentum)face: chin (mentum) sacrum: breechsacrum: breech shoulder: acromion (scapula)shoulder: acromion (scapula)


Varieties of presentation and positionVarieties of presentation and position -Right(R) & Left(L)-Right(R) & Left(L) -anterior(A) , posterior(P) & transverse(T)-anterior(A) , posterior(P) & transverse(T) -occiput(O), chin (mentum(M)) & sacrum(S)-occiput(O), chin (mentum(M)) & sacrum(S) -six vatieties-six vatieties


-If transverse lie -If transverse lie : anterior or posterior & superior or inferior: anterior or posterior & superior or inferior : dificult by clinical examination: dificult by clinical examination : another term back up: another term back up back downback down

FREQUENCY OF THE FREQUENCY OF THE VARIOUS VARIOUS PRESENTATION AND PRESENTATION AND POSITIONPOSITION At or near term: vertex 96% At or near term: vertex 96%

2/3 LOP2/3 LOP breech 3.5% breech 3.5% much greater ealriermuch greater ealrier 14% (GA 29~32wks)14% (GA 29~32wks) face 0.3%face 0.3% shoulder 0.4%shoulder 0.4%

FREQUENCY OF THE FREQUENCY OF THE VARIOUS VARIOUS PRESENTATION AND PRESENTATION AND POSITIONPOSITION Why the term fetus usaully presents by vertex?Why the term fetus usaully presents by vertex?

-uterus: piriform shape-uterus: piriform shape -fetal head > breech-fetal head > breech but. poladic pole > cephalic polebut. poladic pole > cephalic pole (breech+ lower extremities) (head)(breech+ lower extremities) (head) more movablemore movable -after GA 32wks-after GA 32wks amnionic fluid / fetal mass ratio : decreasedamnionic fluid / fetal mass ratio : decreased dependent upon the piriform shape of fetusdependent upon the piriform shape of fetus

FREQUENCY OF THE FREQUENCY OF THE VARIOUS VARIOUS PRESENTATION AND PRESENTATION AND POSITIONPOSITION

-causes of breech: hydrocephalus, uterine septum,-causes of breech: hydrocephalus, uterine septum, extension of vertex columnextension of vertex column placeta- low uterusplaceta- low uterus change normal shapechange normal shape abnomal fetal muscle tone abnomal fetal muscle tone or movementor movement

DIAGNOSIS OF THE FETAL DIAGNOSIS OF THE FETAL PRESENTATION AND PRESENTATION AND POSITIONPOSITION

Abdominal palpation- Abdominal palpation- LEOPOLD MANEUVERSLEOPOLD MANEUVERS - Leopold and sporlin in 1894- Leopold and sporlin in 1894 - the mother should be supine and comfortably- the mother should be supine and comfortably positioned with her abdomen bared positioned with her abdomen bared

- difficult : the patient is obese- difficult : the patient is obese the placenta is anteriorly implantedthe placenta is anteriorly implanted


First maneuverFirst maneuver -contour of the uterus-contour of the uterus -fundus ~ xiphoid -fundus ~ xiphoid 거리거리 -fetal pole in the fundus-fetal pole in the fundus *breech: large*breech: large nodularnodular *head: hard*head: hard roundround more movablemore movable & ballottable& ballottable


Second maneuverSecond maneuver -on either side of the-on either side of the abdomenabdomen -back-back hard ,resistancehard ,resistance ant. vs. post. ant. vs. post. extremitiesextremities numerous small,numerous small, irregular and movileirregular and movile partpart


Third maneuverThird maneuver -using the thumb & finger-using the thumb & finger -above symphisis pubis-above symphisis pubis -differentiation:-differentiation: same as first maneuversame as first maneuver -engage(+): fixed-engage(+): fixed engage(-): movableengage(-): movable -cephalic prominence-cephalic prominence small part: flexionsmall part: flexion back part: extensionback part: extension


Fourth maneuverFourth maneuver -faces the mother’s feet-faces the mother’s feet -the tips of the first-the tips of the first three fingersthree fingers -exert deep pressure-exert deep pressure in the pelvic inletin the pelvic inlet -one hand : rouned body-one hand : rouned body the other: descendingthe other: descending -cephalic prominence-cephalic prominence vertex pre.; small sidevertex pre.; small side face pre.: back sideface pre.: back side


Vaginal examinationVaginal examination - vertex presentation: position and variety- vertex presentation: position and variety by suture & fontanelby suture & fontanel - breech presentation: sacrum & maternal ischial - breech presentation: sacrum & maternal ischial tuberositiestuberosities

1.two fingers are introduced into the vagina.1.two fingers are introduced into the vagina. differentiation of vertex, face, and breechdifferentiation of vertex, face, and breech 2.if vertex presentation2.if vertex presentation the posterior aspect ~ maternal symphysisthe posterior aspect ~ maternal symphysis feel sagittal suture. large & small fontanel feel sagittal suture. large & small fontanel


3.by circular motion3.by circular motion

around the side of the headaround the side of the head

the other fontanel is felt and differentiatedthe other fontanel is felt and differentiated

4.the station, or extent to which the presenting part4.the station, or extent to which the presenting part

has descended into the pelvis at this timehas descended into the pelvis at this time

-in face & breech presentations, error are minimized-in face & breech presentations, error are minimized

because the various parts are distinguished morebecause the various parts are distinguished more

readilyreadily


AuscultationAuscultation

-alone does not provide reliable information-alone does not provide reliable information

-fetal heart sound: through the convex portion-fetal heart sound: through the convex portion

vertex & breech- backvertex & breech- back

face- thoraxface- thorax

-vertex: midway of umbilicus ~ ASIS-vertex: midway of umbilicus ~ ASIS

OA: midlineOA: midline

OT: lateralOT: lateral

OP: back in the flankOP: back in the flank

breech: above the umbilicus breech: above the umbilicus


SonographySonography -without the potential hazards of radiation-without the potential hazards of radiation

LABOR WITHLABOR WITH OCCIPUT OCCIPUT PRESENTATIONSPRESENTATIONS

In the majority of case, the vertex enters the pelvis with In the majority of case, the vertex enters the pelvis with the sagittal suture in the transverse pelvic diameterthe sagittal suture in the transverse pelvic diameter

LOT : 40 %LOT : 40 % ROT ; 20 %ROT ; 20 % -> LOA & ROA- rotated 45 degree-> LOA & ROA- rotated 45 degree OP : 20% OP : 20% ROP > LOPROP > LOP


Occiput anterior presentationOcciput anterior presentation -irregular pelvic shape vs. -irregular pelvic shape vs. large dimensions of the mature fetal headlarge dimensions of the mature fetal head -adaptation, accommodation-adaptation, accommodation -the cardinal movements of labor-the cardinal movements of labor engagement, descent, flexion. Intermal rotation,engagement, descent, flexion. Intermal rotation, extension. external rotation, expulsionextension. external rotation, expulsion ->a combination of movements ->a combination of movements -fetal ovoid-> cylinder-fetal ovoid-> cylinder


1. Engagement1. Engagement ; BPD passes through the pelvic inlet; BPD passes through the pelvic inlet -”floating” : the fetal head is freely movable above-”floating” : the fetal head is freely movable above the pelvic inlet at the onset of labor the pelvic inlet at the onset of labor -the fetal head usually enters the pelvis inlet either-the fetal head usually enters the pelvis inlet either in the transverse diameter or in one of the obliquein the transverse diameter or in one of the oblique diametersdiameters --asynclitismasynclitism the deflection of the head to a more anterior orthe deflection of the head to a more anterior or posterior position in the pelvisposterior position in the pelvis


2. Descent2. Descent -nullipara: engagement –bofore labor-nullipara: engagement –bofore labor descent- the second stagedescent- the second stage multipara: descent – begins with engagementmultipara: descent – begins with engagement -pressure of the amnionic fluid-pressure of the amnionic fluid direct pressure of the fundus upon the breechdirect pressure of the fundus upon the breech with contrantionwith contrantion bearing down efforts with the abdominal musclesbearing down efforts with the abdominal muscles extension and straightening of the fetal bodyextension and straightening of the fetal body


3. Flexion3. Flexion - occipitofrontal- occipitofrontal ▼ ▼ suboccipitobregmaticsuboccipitobregmatic

-chin: contact with -chin: contact with the fetal thoraxthe fetal thorax


4. Internal rotation4. Internal rotation -a turning of the head by the time the head reaches-a turning of the head by the time the head reaches the pelvic floorthe pelvic floor -the occiput gradually moves from its original-the occiput gradually moves from its original position anteriorly toward the symphysis pubisposition anteriorly toward the symphysis pubis -essential for the completion of labor-essential for the completion of labor


5. Extension5. Extension -essential to birth-essential to birth -the base of the occiput into direct contact with-the base of the occiput into direct contact with inferior margin of the symphysis pubisinferior margin of the symphysis pubis -vulvar outlet: upward & forward-vulvar outlet: upward & forward


6. External rotation6. External rotation -after head delivery, the occiput was directed-after head delivery, the occiput was directed toward the left (original direction)toward the left (original direction)

-bisacromial diameter into relation with the -bisacromial diameter into relation with the anteroposterior diameter of the pelvic outletanteroposterior diameter of the pelvic outlet

7. Expulsion7. Expulsion -ant. shoulder: under the symphysis pubis -ant. shoulder: under the symphysis pubis post. shouider: the perineum post. shouider: the perineum


Occiput posterior positionOcciput posterior position -the occiput has to rotate to the symohysis pubis -the occiput has to rotate to the symohysis pubis through 135 degreethrough 135 degree -does not take place, -does not take place, persistent occiput posteriorpersistent occiput posterior

CHANGES IN SHAPECHANGES IN SHAPE OF THE FETAL OF THE FETAL HEADHEAD

Caput succedaneumCaput succedaneum -before complete cervical dilatation, become-before complete cervical dilatation, become edematous and forming a swellingedematous and forming a swelling

-more commonly, in the lower portion of the-more commonly, in the lower portion of the birth canalbirth canal LOT: Rt parietal boneLOT: Rt parietal bone ROT: Lt parietal boneROT: Lt parietal bone

CHANGES IN SHAPECHANGES IN SHAPE OF THE FETAL OF THE FETAL HEADHEAD

MoldingMolding -the change in fetal head shape from external-the change in fetal head shape from external compressive forcescompressive forces

-shortened suboccipitobregmatic diameter-shortened suboccipitobregmatic diameter lengthening of the mentovertical diameterlengthening of the mentovertical diameter

ch 12. mechanisms of normal labor 부산백병원 산부인과 r1 서 영 진

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