Transcript MULTIPLE PREGNANCY
Lecture 5
PHASES OF PARTURITION STAGES OF LABOR MECHANISM OF NORMAL LABOR IN OCCIPUT PRESENTATION
Prof. Vlad TICA, MD, PhD
PHASES OF PARTURITION
Labor : uterine contractions that effect dilatation of cervix and force fetus through birth canal Parturition: bringing forth of young, encompass all physiological processes involved in birthing Phase 0: Prelude to Parturition Phase 1: Preparation for Labor Phase 2: Process of Labor Phase 3: Parturition Recovery
PHASES OF PARTURITION & ONSET OF LABOR
Divide 4 uterine phases: correspond to major physiological transient of myometrium and cervix during pregnancy
PHASE 0: UT QUIESCENCE
Uterine smooth m tranquility with maintenance of cervical structural integrity Unresponsive to natural stimuli, contractile paralysis Myometrium : quiescent state Cervix : firm unyielding Successful anatomical structural integrity :essential for successful parturition Some myometrial contraction occur not cause cervix dilation Braxton-Hicks contraction / false labor
PHASE 0: UT QUIESCENCE
Braxton – Hicks contraction or false labor • myometrial contractions that do not cause cervical dilatation • unpredictability in occurrence • lack of intensity • brevity of duration • discomfort – confined to low abdomen & groin
PHASE 1: PREPARATION FOR LABOR
Uterine awakening or activation Progression of change in uterus during last 6-8 weeks of pregnancy Cervical change Myometrial change
PHASE 1: PREPARATION FOR LABOR
CERVICAL CHANGE Initiation of parturition: Cx soften, yield, more readily dilatable Fundus transformed to produce effective contraction that drive fetus through Cx & birth canal Failure of coordinated interaction outcome unfavorable preg
PHASE 1: PREPARATION FOR LABOR
CERVICAL CHANGE Change of state of bundles of collagen fiber Collagen breakdown & rearrangement of collagen fiber bundles (number & size) Chages in relative amount of glycosaminoglycans (hyaluronic acid, capacity of Cx to retain water) Dermatan sulfate (need for collagen fiber cross linking) Production of cytokine degrade collgen Cx thinning, softening relaxation diatation Cx initiate
PHASE 1: PREPARATION FOR LABOR
CERVICAL CHANGE PG E2 & F2a : modification of collagen & alteration in relative amount of glycosaminoglycans Cx softening or ripenning to facilitate induction of labor
PHASE 1: PREPARATION FOR LABOR
MYOMETRIAL CHANGE Increase Ut irritability & responsiveness to uterotonins Alterations in expression of key enzyme CAP (contraction-associated proteins) - control myometrium contractility Myometrial oxytocin R Myometrial cell gap junction protein (ex connexin -43) Formation lower Ut segment
PHASE 2 : PROCESS OF LABOR
Active labor : Ut contrations bring about progressive cervical dilatation & delivery 3 stage of labor
PHASE 2: PROCESS OF LABOR
1 st STAGE OF LABOR begins when uterine contraction of sufficient frequency, intensity & duration ends when Cx is fully dilatated (10cm) stage of cervical effacement & dilatation 2 nd STAGE OF LABOR begins when complete dilatation of Cx ends with delivery of fetus stage of expulsion of fetus
PHASE 2: PROCESS OF LABOR
3 rd STAGE OF LABOR begins after delivery of fetus ends with delivery of placenta and fetal membranes stage of separation & expulsion of placenta 4 th STAGE OF LABOR begins after placenta and fetal membranes ends after 2 hours stage of immediate puerperium
PHASE 2: PROCESS OF LABOR
PHASE 2: PROCESS OF LABOR
1
st
STAGE OF LABOR: CLINICAL ONSET OF LABOR
Formation of distinct lower & upper Ut segment: • 2 distinct parts (anatomically & physiologically) 1. UPPER SEGMENT actively contracting becomes thicker as labor advances quite firm or hard 2. LOWER SEGMENT relatively passive develops into a much thinly walled passage for the fetus much less firm
SEQUENCE OF DEVELOPMENT OF SEGMENT & RING IN UTERUS IN PREGNANT WOMEN AT TERM & IN LABOR
Cx near end of pregnacy before labor Beginning effacement of Cx
Further effacement of Cx Cervical canal obliterated
CERVICAL CHANGE INDUCED DURING 1 st STAGE OF LABOR
CERVICAL CHANGE INDUCED DURING 1
st
STAGE OF LABOR
2 phases of cervical dilatation: •
1. LATENT PHASE
more variable • subject to sensitive changes by extraneous factors & by sedation (prolongation) & myometrial stimulation (shortening) • • •
2. ACTIVE PHASE
acceleration phase - usually predictive of outcome phase of maximum slope deceleration phase
2
nd
STAGE OF LABOR: FETAL DESCENT
• In many nulliparas • engagement accomplished before labor begins • further descent not occur until late in labor • increased rates of descent are ordinarily observed during the phase of maximum slope
2
nd
STAGE OF LABOR: FETAL DESCENT
2
nd
STAGE OF LABOR: FETAL DESCENT
Labor course divided fuctionally on basis of expected evolution of dilatation & descent curves into 3 divisions: PREPARATORY DIVISION - latent & acceleration phases DILATATIONAL DIVISION - phase of maximum slope of cervical dilatation - most rapid rate of dilatation occur PELVIC DIVISION - deceleration phase & second stage while concurrent with phase of maximum slope of fetal descent
3
rd
STAGE OF LABOR:
DELIVERY OF PLACENTA & MEMBRANES
4
th
STAGE OF LABOR: IMMEDIATE PUERPERIUM
PHASE 3 OF PARTURITION:
PROCESS OF LABOR
Immediately after delivery & for 2 hours or so thereafter, myometrium in state of rigid & persistent contraction & retraction effect compression of large Ut vessels Severe PPH prevented Involution of Ut & reinstitution of ovulation Complete Ut involution : 4~6 wks Infertility persist as long as breast feeding is continued ( lactation anovulation & amenorrhea)
LIE, PRESENTATION, ATTITUDE & POSITION
FETAL LIE The relation of the long axis of the fetus to that of the mother Longitudinal lie - found in 99% of labours at term Transverse lie - multiparity, placenta praevia, hydramnios, uterine anomalies Oblique lie : unstable (become logitudinal or transversal) By abdominal palpation, vaginal examination, and auscultation, or by technical means (USG, X-ray)
LIE, PRESENTATION, ATTITUDE & POSITION
FETAL PRESENTATION The presenting part is the portion of the body of the fetus that is foremost in the birth canal The presenting part can be felt through the cervix on vaginal examination Longitudinal lie cephalic presentation breech presentation Transverse lie shoulder presentation
LIE, PRESENTATION, ATTITUDE & POSITION
CEPHALIC PRESENTATION Head is flexed sharply vertex / occiput presentation Head is extended sharply face presentation Partially flexed presentation) bregma presenting (sinciput Partially extended brow presentation
LIE, PRESENTATION, ATTITUDE & POSITION
BREECH PRESENTATION Frank breech Complete breech Footling breech
LIE, PRESENTATION, ATTITUDE & POSITION
ATTITUDE Posture of the fetus shape of the uterus folded on itself to accommodate the Flexed head, thighs, knees &feet The arms crossed over the chest Face presentation extended concave contour of the vertebral column
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' I ! 1 \ i i B 1 1 A F c
D (A) vertex (B) sinciput (C) brow (D) face
Longitudinal lie. Cephalic presentation. Differences in attitude of fetal body , Note changes in fetal attitude in relation to fetal vertex as the fetal head becomes less flexed
I I Longitudinal lie. Frank breech presentation.
Longitudinal lie. Complete breech presentation.
Longitudinal lie. Incomplete, or footling, breech presentation
POSITION
The relation of an arbitrary chosen point of the fetal presenting part to the Rt or Lt side of the maternal birth canal The chosen point: Vertex presentation Face presentation occiput mentum Breech presentation sacrum Each presentation has 2 positions: Rt or Lt Each position has 3 varieties : anterior, transverse, posterior OA ROA LOA ROT ROP OP LOP LOT
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' t J
LONGITUDINAL LIE VERTEX PRESENTATION
LOA LOP
s A
Right occiput posterior (ROP) Right occiput transverse (ROT)
Longitudinal lie. Vertex presentation
w
c a l t a t ~ h t p ( f i t t b f e
w
C c !
S f a Right occiput anterior (ROA)
FREQUENCY OF VARIOUS PRESENTATIONS & POSITIONS AT TERM
Vertex 2/3 96% Lt 1/3 Rt Breech 3.5% Face 0.3% Shoulder 0.4%
Left mento-anterior Right mento-anterior Right mento-posterior
Longitudinal lie. Face presentation. Left and right anterior and posterior positions.
~ Longitudinal lie. Breech presentation LSP
Transverse lie. Right acromio-dorso-posterior position (RADP). The shoulder of the fetus is to the mother's right, and the back is posterior
MECHANISM OF LABOUR WITH OCCIPUT PRESENTATIONS THE CARDINAL MOVEMENTS OF LABOUR
1 - ENGAGEMENT The greatest transverse diameter BPD passes through the pelvic inlet It may occur in the last few weeks of pregnancy or only in labour especially in multipara The fetus enters the pelvis in transverse or oblique diameter LOT 40% ROT 20% OP 20% ROP > LOP ROA / LOA 20%
THE CARDINAL MOVEMENTS OF
Asynclitism
LABOUR
The sagittal sutures of the head deflects ant towards the symphysis pubis or post towards the sacrum 2 - DESCENT In nullipara engagement takes place before the onset of labour & further descent may not occur till the 2 nd stage In multipara descent begins with engagement It is gradually progressive till the fetus is delivered It is affected by the uterine contractions & thinning of the lower segment
Anterior asynclitism Naegele's obliquity Normal synclitism Posterior asynclitism Litzmann's obliquity Ear presentation
3-FLEXION
The descending head meets resistance of pelvic floor, Cx & walls of the pelvis flexion The shorter suboccipito-begmatic is substituted for the longer occipito-frontal
Lever action producing flexion of the head; conversion from occipito-frontal to suboccipito-bregmatic diameter typically reduces the anteroposterior diameter from nearly 12 to 9.5 cm
4 degrees of head flexion
c A Indicated by the solid line the occipitomental diameter; the broken line connects the center of the anterior fontanel with posterior fontanel: A. Flexion poor B. Flexion moderate C. Flexion advanced D. Flexion complete Note that with flexion complete the chin is on the chest, and the A c D suboccipitobregmatic diameter, the shortest anteroposterior diameter of the fetal head, is passing through the pelvic inlet
4-INTERNAL ROTATION
Turning of the head from the OT position towards the symphysis pubis ie. Occiput moves from transverse to anterior 45º anteriorly Less commonly OT 135º posteriorly towards the sacrum It is not accomplished till the head has reached the spines The levator ani muscles form a V shaped sling that tend to rotate the vertex anteriorly It is completed by the time the head reaches the pelvic floor 2/3 or shortly after ¼
EXTENSION
When the flexed head reaches the vulva it undergoes extension the base of the occiput will be in direct contact with the inferior margin of the symphysis pubis Crowning the largest diameter of the fetal head is encircled by the vulvar ring The head is born by further extension as the occiput, bregma, forehead, nose, mouth & chin pass successively over the perineum
EXTERNAL ROTATION RESTITUTION
After delivery of the head it returns to the position it occupied at engagement, the natural position relative to the shoulders (oblique position) Then the fetal body will rotate to bring one shoulder anterior behind the symphysis pubis (biacromial diameter into the APD of the pelvic outlet) Restitution is followed by complete external rotation to transverse position (occiput lies to next to left maternal thigh) The anterior shoulder slips under the pubis By lateral flexion of the fetal body the post shoulder will be delivered & the rest of the body will follow
3 0 2
2.Engagement;descent, flexion 3. Further descent, internal rotation 6. Restitution (external rotation)
Cardinal movements in the mechanism of labor and delivery, left occiput anterior position
4. Complete rotation, beginning extension
a f s
3 0 4
F t l v b Mechanism of labor for the left occiput transverse position, lateral view. Posterior asynclitism (A) at the pelvic brim followed by lateral flexion, resulting in anterior asynclitism (B) after engagement, further descent (C), rotation, and extension (D)
OCCIPUT POSTERIOR POSITION
Mechanism of labour is identical to OT & anterior varieties The occiput rotate to the symphysis pubis through 135º instead of 90º or 45º If rotation does not occur direct occiput posterior or partial rotation transverse arrest
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, , 0 Mechanism of labor for right occiput posterior position, anterior rotation