Mechanisms of labor

Dr.F Mostajeran

Mechanisms of labor

Lie presentation Attitude and position

Fetal lie: Longitudinal Oblique

F . Presentation

Cephalic

Breech

Shoulder (preria-septum)

Relationship head and body classified

Chin contact thorax vertex, occiput

presentation occiput and back contact , face

presentation F. head position between these

partially flexed , fontanel (bregma) , sinciput

presentation partially extended , brow

Breech presentation

Frank

Complete

Footling

Fetal attitude or posture Fetus forms an avoid Back Head Legs Arms

Position :

Presenting part Vertex → occiput Face →mentum Breech →sacrum Lo Ro oA oP

Diagnosis presentation – position

Abdominal palpation:

Leopold maneuvers First maneuver Second maneuver fetal fole Third maneuver thumb – fingers ,movable Fourth maneuver First three fingers Direction of axis pelvic inlet

V. E xamination

Sutures

Fontanels

Auscultation reinforce

V.S

Radiography

Labor with occiput presentation vertex presentation 40% LOT 20% ROT 20% OP

OP (placenta anterior –narrow fore pelvis)

Cardinal morement of labor Engagement Descent Flexion Internal rotation Extension External rotation Expulsion

Changes in shape of the head Caput succedaneum

Vertex → head change shape → labor forces

Fetal scalp → forming swelling prevent differentiation sutures

fontanels

Molding

Head shape change → external compressive forces possibly → Braxton hicks cont

Admission procedures

Urged to report early in laborEarly admittance to labar , delivery

unit especially high risk pregnancyaccurat diagnosis of labarFalsely diagnosed , inappropriate in

terrentionNot diagnosed (remot from medical

personnel medical facilities)

Definition of labor

Uterine contractions that bring effacement and dilatation of cervix.

Painful contractions become regular onset of labor as beginning at the time

of admission to the labor unitAdmission for labor based on dilatations

accompanied by painful contractions .

D. Diagnasis between false and true labor is

difficult Contractions of true laborRegular intervalsIntervals gradually shortenIntensity gradually increasesDiscomfort back , abdomenCervix dilatesDiscomfort is not stopped by

sedation

Contractions of false labor

Irregular intervalsIntervals longIntensity unchangedDiscomfort lawer abdomen Cervix not dilate Relieved by sedation

Pregnant woman who is having

CantractionsEmergency conditionLabor is defined as process of

childbirth beginningLatent phase delivery placenta

Electronic admission testing

Recommend NST or CST on all patient

(labar – delivery unit)Fetal admission test identify unsuspected cases

Vaginal examination1. Amnionic fluid effacement2. Cervix dilatation position3. Presenting part4. Station5. Pelvic architecture

Detection of ruptured membranes

Leakage of fluidProlapse cordLabor occurSerious intra uterine infectionNitrazine paper (PH= 7.0 – 7.5)Arborization or ferningAlpha – fetoproteinInjection various dyes

Vital signs and review of pregnancy record

Physical examinationPreparation of vulva and perineumInspection and cleaning of the vulva

, perineum , mini – shave - enema

Friedman Three functional divisions of labor Preparatory division: Little cervical dilatation Considerable change Dilatational division : Most rapid rate pelvic division: Deceleration phase of cervix -

dilatation Cardinal fetal movements

Latent phase (14-20h)Active phase:

acceleration ,phase of maximum slope

, deceleration phase

Cervical dilatationCervical dilatation

Management first stage of labor

Remainder of general physical exam is completed

HCT HB protein - glocoseaverage duration first stage of

labor7 hours in nulliparous w4 hours in parous w

Fetal monitoring during labarContractions and response FHSuitable stethoscopc , doppler

ultrasonic devicesFH should be checked after

contractionsevery 30 minutes (15)Second stage every 15 minutes (5) Cantinous electronic monitoring

MATERNAL MONITORING

Vital signsT , pulse , BP every 4/hPROM temprature every 1/h18 h of PROM antimicrobial

Subsequent vaginal examinations

When membrans rupture if head was not Defenetly engaged

fetal H immediately and during the next uterine contraction

(occult umbilical cord compression)

periodic examinations at 2-3 hours interval

Oral intakeGastric emptying time prolanged

(food – medication remain in the stomach – not absorbed may be vomited)

Food should be withheld

Intravenous fluidsInfusion system routine early labar (IV

line)Longer labors glucose sodium water 60-

120 ml/hr

Maternal position during labor

normal laboring womanNot be confined to bedComfortable chairIn bed position most comfortabl

(lateral recumbend)

AnalgesiaIs initiated on the basis of maternal discomfortvaginal examination befor

administration of analgesia (delivering a depressed infant)Timing , method and size of initial

and subsequent dose , interval of time until delivery

Amniotomy

There is a great temptationBenefits: rapid labor detection of

meconium staining Internal fetal MAseptic techniqueHead must be well applied to the

cerxin

Urinary bladder functionBladder distention avoidAbstracted laborSubsequent bladdes hypotonia, infectionSuprapubic region shauld be visualized ,

palpated detect filling bladderIf could not void on a bedpanIntermittent catheterization

Management of second stage labor

Full dilatation of the cervixBegins to bear dawn50 minutos in nulliparous20 minutos in multiparous

Higher parity 2-3 expulsive efforts may suffice Complete the delivery of the infant

FHRLow – risk 15 H.risk 5

Fetal H.RContraction – maternal expulsive efforts FHR are not consequence of head

compressionDescent fetus and reduction in uterine

volume some degree of premature separation

placenta

tighten a loop or loops of umbilical cord

Around the fetus umbilical blood flow

Prolonged uninterrupted maternal expulsive efforts dangerous to the fetus

Preparation for deliveryVariety of positionsDorsal lithotomy positionFor beter exposure legholders stirrupsCramps in the legs (brief massage –

changing position)Preparation for delivery entails vulvar

and perineal cleansing

Spontaneous delivery

Delivery of the headContraction perineum bulgesVulvovaginal opening becomes more

dilatedGradually circular opening This encirclement of the largest headBy the vulvar ring is known as

crowning

Perineum is extremely thinEpisiotomy , lacerationEpisiotomy risk tear external anal

– rectumEpisiotomy - anterior tear

urethra , labia

Ritgen manover

Vaginal introitus 5 cmTowel – draped , gloved hand

forward pressureon the chin of the fetusother hand exerts pressure

superiorly against occiput

Cleaning the nasopharynxMinimize aspiration AF – debris

, bloodonce thorax is delivered face quickly wiped nause ,

mouth are aspirated

Following delivery of anterior shoulderFinger should be passed to the neckNuchal cords 25% +Drawn down , loose – slipped over the

head

Clamping the cord4-5 cm , 2-3 cm fetal abdomen two

clampsPlastic cord clamp

Timing of cord clamping

Infant is placed at or below vaginal interoitus 3 , 80ml of blood shifted from placenta to infant

80ml 50mg Iron , Iron deficiency anemiaMaternal alloimmunization our policy after cleaning airway

30" cord clamp

Management of the third stage

After delivery of the infantHeight uterine fundusUterus firm , no unusual bleedingWaiting until placentac separat –

no massageHand rest on the fundus (atonic –

filled with blood)

Signs of placental separation

1. uterus becames globular firm

2. Sudden gush of blood

3. Uterus rises (placenta separated , passes dawn to lower u-segment

4. Its balk pushes uterus upward

5. Umbilical cord protrudes forther out

delivery of the placentaTraction on the umbilical cord must not

be used inversionManaol removal of placentaoccasionally placenta will not separatAt any time brisk bleeding and , placenta

can not be deliveredActive management of the third stage5 units oxytocin +0.5 ergometrine reductian in the length of third stage

Fourth stage of labor

Exam placenta , membranes , umbilical cord

Completeness , anomaliesHour immediately fallowing deliveryCritical fourth stage of labor uterine atony , BP , pulse every 15

Oxytocic AgentsOxytocin (pitocin , syntocinon)Methylergo novine maleat

(methergine)Reduce blood loss by stimuloting

myometrial contractionIml 10IU half – lifc IV 3Inapropriate dose kill the

fetus ,rupture uterus

Cardiovascular effectsDeleterious effects follow IV bolusAntidiuresisrare maternal convulsion antidiuretic

actionWater intoxication (20,40mu/minut )Concentration should be increared rather

than rate of flowNormal saline are lactated ringer solution

Ergonovine and methylergonavineIV – IM – orally no differenc in actionsSensitivity of pregnant uterus is very greatIn pregnancy 0.1my IV , 0.25my oral

tetanic Uterine contractionTetanic effect prerention , control PPHIV administration sometimes

tram sient , severe hypertension

ProstaglandinsNot used routinely Manage ment PPHPG F2x 250ng IM (15-90" ) 8does

88% successful20% side effects

diarrhea ,hypertension vomiting , Fever , flushing , tachycandia

PG E2 20-mg suppositories

Lacerat ons of the Birth canal

ClassifiedFirst fourchette , perineal skin

vaginal mucousSecond fascia and muscles of

perineal bodyThird anal sphincterFourth retal mucosa

Episiotomy and repairIncision of pudendaPerineotomy incision of perineuEpisiotamy synonymously with

penineotomyBegin in midline :Directed laterally mediolateralDirected down ward midline

Timing of episiotomyPerform when head is visible during

contraction 3-4After application of bladesTiming of repairMost common practice repair until

placenta deliveredTechniqueHemostasisAnatomical restoration without

excessive suturingChromic catgut 3-0

Fourth – degree laceration

Various techniques remcommendEsential approximat torn edges

rectal mucosaWith muscularis sutures 0.5cm

apartMuscular layer covered with a

layer of fascia

Labor with occiput presentations

95% fetus occiput or vertex presentation

Most commonly ascertained ab – examConfirmed V.Examination before or at

the onset of laborSagitlal suture in the transrevse pelvic

diameterLOT , ROT , LOA , ROAROP , LOP (narrow forepelvis , anterior

placentation

OCCCIPUT ANTERIOR PRESENTATION

Irregular shape pelvic canalLarge dimensions fetal headAdoptation or accommodation

of suitablePortions of head to the varius

segment of the pelvis is required

Cardinal movements of labar

EngagementDescentFlexionInternal rotationExtensionExternal rotation expulsion

Concomitantly , uterine cantractions

Important modifications in fetal attitude

straightening of the fetus loss dorsal convexity , closer application of the extremities to the body , fetal ovoid cylinder

EngagementBiparietal diameter – greatest transverse

diameter F.Head passes thraugh the pelvic inlet

Lost few weeks of pregnancyUntil after cammencement of laborIn many multiparous , some nulliparousAt onset of labor head freely movable

above inletReferred “floating”

Asynclitism

Sagittal suture remaining parallel to transverse axis may not lie exactly midway

Between symphysis and sacral promontory

Sagitlal suture deflected posteriorly or anteriorly

Asynclitism anteror or posteriorModerat degree of asynclitism

are the rule in normal laborSevere asynclitism may lead to

cephalopelvic disproportion even with an normal – sized pelvis

DESCENT

First requisit for birth infant In nulli parus take place befor

the onset of laborFurther descent until onset of

the second stageIn multiparous descent usually

begins with engagement

Descent is brought by one or more of four forces

1. Pressure of amnionic fluid

2. Direct pressure of fondus with cont ractions

3. Bearing down efforts abdominal muscles

4. Extension and straightening of fetal body

FLEXION

As soon as descending head meets resistance

Cervix , walls of the pelvis , pelvic floor

The chin is braught into more intimate contact Fetal thorox

suboccipitobreg matic occipitafrontal

Internal rotation

occiput gradually moves from original position toward symphysis pubis

Less commonly posteriorlyInternal rotation essential

completion of laborIt always associated with descent

and acomplished after engagement

ExtensionAfter in-rotation sharply flexed

head reaches the vulvaUndergoes extension which

essential to birthVulvar outlet directed upward ,

for wardExtension must occur before

head can pass through it

Head born by further extension occiput , bregma , fore head ,

nose mouthFinally chin passHead drops down ward chin lies

over anal region

External rotationdelivered head under goes restitutionocciput toward the left rotates left

ischial tuberosityocciput toward the right rotates

right ischial tuberosityBisacromial diameter in to relation

anteroposterior diameter of the pelbic outlet shoulders (anteriar – posterior)

ExpulsionImmediatly after external

rotationAnterior shoulder under

symphysis pubisPosterior shoulder distended

perineumAfter delivery of the shouldersRest of body quickly extruded