Transcript Ch 12. Mechanisms of normal labor

Ch 12. Mechanisms of
normal labor
부산백병원 산부인과
R1 서 영 진
LIE, PRESENTATION,
ATTITUDE, AND POSITION
 By abdominal palpation, vaginal examination,
and auscultation, or by technical means
(USG, X-ray)
 Fetal lie
-the relation of the long axis of the fetus to
that of the mother
-longitudinal (99% at term)
transverse : multipara, pl revia
hydramnios, Ut anomalies
oblique: unstable (become logitudinal or
transv.)
LIE, PRESENTATION,
ATTITUDE, AND POSITION
 Fetal presentation
-the foremost portion of the body of the fetus
within the birth canal
-can be felt through the cevix on vaginal exam.
-longitudinal lie: head (cephalic presentation)
breech (breech presentation)
transverse lie: shoulder
LIE, PRESENTATION,
ATTITUDE, AND POSITION
# Cephalic presentation
-Ordinarily, the head is flexed sharply so that
the chin is in contact with the thorax
-the occipital fontanel is the presenting part
-referred to as a vertex or occipital presentation
-extended so that the occiput is in contact with the
back : face
sinciput (ant. fontanel or bregma)
brow
-sinciput, brow: transient -> vertex or blow
LIE, PRESENTATION,
ATTITUDE, AND POSITION
# Breech presentation
-frank: the thighs are flexed and the legs extended
over the anterior surface of the body
complete: the thighs are flexed on the abdomen
and the legs upon the thighs
incomplete: the lowermost part is one or both feet,
or one or both knees (footling)
LIE, PRESENTATION,
ATTITUDE, AND POSITION
 Fetal attitude or posture
-the fetus forms an ovoid mass that corresponds
roughly to the shape of the uterine cavity
-back: markedly convex
head: flexed (chin-chest)
thighs: flexed over the abdomen
legs: bent at the knee
feet: flexed (ant. surfaces of the legs) at the ankle
arms: crossed or parallel over the thorax
-face presentaton: concave (extended) of the
vertabral column
LIE, PRESENTATION,
ATTITUDE, AND POSITION
 Fetal position
- the relation of arbitrarily chosen portion of the
fetal presenting part to the right or left side of
the maternal birth canal
- Rght vs. Left
-vertex: occiput
face: chin (mentum)
sacrum: breech
shoulder: acromion (scapula)
LIE, PRESENTATION,
ATTITUDE, AND POSITION
 Varieties of presentation and position
-Right(R) & Left(L)
-anterior(A) , posterior(P) & transverse(T)
-occiput(O), chin (mentum(M)) & sacrum(S)
-six vatieties
LIE, PRESENTATION,
ATTITUDE, AND POSITION
-If transverse lie
: anterior or posterior & superior or inferior
: dificult by clinical examination
: another term back up
back down
FREQUENCY OF THE VARIOUS
PRESENTATION AND POSITION
 At or near term: vertex 96%
2/3 LOP
breech 3.5%
much greater ealrier
14% (GA 29~32wks)
face 0.3%
shoulder 0.4%
FREQUENCY OF THE VARIOUS
PRESENTATION AND POSITION
 Why the term fetus usaully presents by vertex?
-uterus: piriform shape
-fetal head > breech
but. poladic pole
>
cephalic pole
(breech+ lower extremities)
(head)
more movable
-after GA 32wks
amnionic fluid / fetal mass ratio : decreased
dependent upon the piriform shape of fetus
FREQUENCY OF THE VARIOUS
PRESENTATION AND POSITION
-causes of breech: hydrocephalus, uterine septum,
extension of vertex column
placeta- low uterus
change normal shape
abnomal fetal muscle tone
or movement
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Abdominal palpation- LEOPOLD MANEUVERS
- Leopold and sporlin in 1894
- the mother should be supine and comfortably
positioned with her abdomen bared
- difficult : the patient is obese
the placenta is anteriorly implanted
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 First maneuver
-contour of the uterus
-fundus ~ xiphoid 거리
-fetal pole in the fundus
*breech: large
nodular
*head: hard
round
more movable
& ballottable
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Second maneuver
-on either side of the
abdomen
-back
hard ,resistance
ant. vs. post.
extremities
numerous small,
irregular and movile
part
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Third maneuver
-using the thumb & finger
-above symphisis pubis
-differentiation:
same as first maneuver
-engage(+): fixed
engage(-): movable
-cephalic prominence
small part: flexion
back part: extension
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Fourth maneuver
-faces the mother’s feet
-the tips of the first
three fingers
-exert deep pressure
in the pelvic inlet
-one hand : rouned body
the other: descending
-cephalic prominence
vertex pre.; small side
face pre.: back side
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Vaginal examination
- vertex presentation: position and variety
by suture & fontanel
- breech presentation: sacrum & maternal ischial
tuberosities
1.two fingers are introduced into the vagina.
differentiation of vertex, face, and breech
2.if vertex presentation
the posterior aspect ~ maternal symphysis
feel sagittal suture. large & small fontanel
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
3.by circular motion
around the side of the head
the other fontanel is felt and differentiated
4.the station, or extent to which the presenting part
has descended into the pelvis at this time
-in face & breech presentations, error are minimized
because the various parts are distinguished more
readily
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Auscultation
-alone does not provide reliable information
-fetal heart sound: through the convex portion
vertex & breech- back
face- thorax
-vertex: midway of umbilicus ~ ASIS
OA: midline
OT: lateral
OP: back in the flank
breech: above the umbilicus
DIAGNOSIS OF THE FETAL
PRESENTATION AND POSITION
 Sonography
-without the potential hazards of radiation
LABOR WITH
OCCIPUT PRESENTATIONS
 In the majority of case, the vertex enters the pelvis
with the sagittal suture in the transverse pelvic
diameter
 LOT : 40 %
ROT ; 20 %
-> LOA & ROA- rotated 45 degree
OP : 20%
ROP > LOP
LABOR WITH
OCCIPUT PRESENTATIONS
 Occiput anterior presentation
-irregular pelvic shape vs.
large dimensions of the mature fetal head
-adaptation, accommodation
-the cardinal movements of labor
engagement, descent, flexion. Intermal rotation,
extension. external rotation, expulsion
->a combination of movements
-fetal ovoid-> cylinder
LABOR WITH
OCCIPUT PRESENTATIONS
1. Engagement
; BPD passes through the pelvic inlet
-”floating” : the fetal head is freely movable above
the pelvic inlet at the onset of labor
-the fetal head usually enters the pelvis inlet either
in the transverse diameter or in one of the oblique
diameters
-asynclitism
the deflection of the head to a more anterior or
posterior position in the pelvis
LABOR WITH
OCCIPUT PRESENTATIONS
2. Descent
-nullipara: engagement –bofore labor
descent- the second stage
multipara: descent – begins with engagement
-pressure of the amnionic fluid
direct pressure of the fundus upon the breech
with contrantion
bearing down efforts with the abdominal muscles
extension and straightening of the fetal body
LABOR WITH
OCCIPUT PRESENTATIONS
3. Flexion
- occipitofrontal
▼
suboccipitobregmatic
-chin: contact with
the fetal thorax
LABOR WITH
OCCIPUT PRESENTATIONS
4. Internal rotation
-a turning of the head by the time the head reaches
the pelvic floor
-the occiput gradually moves from its original
position anteriorly toward the symphysis pubis
-essential for the completion of labor
LABOR WITH
OCCIPUT PRESENTATIONS
5. Extension
-essential to birth
-the base of the occiput into direct contact with
inferior margin of the symphysis pubis
-vulvar outlet: upward & forward
LABOR WITH
OCCIPUT PRESENTATIONS
6. External rotation
-after head delivery, the occiput was directed
toward the left (original direction)
-bisacromial diameter into relation with the
anteroposterior diameter of the pelvic outlet
7. Expulsion
-ant. shoulder: under the symphysis pubis
post. shouider: the perineum
LABOR WITH
OCCIPUT PRESENTATIONS
 Occiput posterior position
-the occiput has to rotate to the symohysis pubis
through 135 degree
-does not take place, persistent occiput posterior
CHANGES IN SHAPE
OF THE FETAL HEAD
 Caput succedaneum
-before complete cervical dilatation, become
edematous and forming a swelling
-more commonly, in the lower portion of the
birth canal
LOT: Rt parietal bone
ROT: Lt parietal bone
CHANGES IN SHAPE
OF THE FETAL HEAD
 Molding
-the change in fetal head shape from external
compressive forces
-shortened suboccipitobregmatic diameter
lengthening of the mentovertical diameter