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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

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Ch 12. Mechanisms of normal labor

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  1. Ch 12. Mechanisms of normal labor 부산백병원 산부인과 R1 서 영 진

  2. 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.)

  3. 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

  4. 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

  5. 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)

  6. 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

  7. 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)

  8. 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

  9. LIE, PRESENTATION, ATTITUDE, AND POSITION -If transverse lie : anterior or posterior & superior or inferior : dificult by clinical examination : another term back up back down

  10. 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%

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. DIAGNOSIS OF THE FETAL PRESENTATION AND POSITION • Sonography -without the potential hazards of radiation

  22. 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

  23. 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

  24. 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

  25. 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

  26. LABOR WITH OCCIPUT PRESENTATIONS 3. Flexion - occipitofrontal ▼ suboccipitobregmatic -chin: contact with the fetal thorax

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

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