The Intrapartum Period

Normal Labor

 

Objectives

•      Examine 4 critical factors that influence labor

•      Discuss the physiology of labor

•      Discuss the premonitory signs of labor

•      Differentiate between true and false labor

•      Discuss maternal and fetal response to labor

•      Describe changes occurring in each phase of labor

 

Definition

•      The period of time surrounding birth

 

Labor begins...

•      EDD plus/minus 2 weeks

 

Critical Factors in Labor

•      Birth Passage

•      Fetus

•      Primary Forces

•      Psychosocial considerations

 

Birth Passage

•      Pelvis

–   Size

–   type

•      nature of soft tissues

–   Cervix to dilate and efface

 

Shape and Structure of Maternal Pelvis

•      divided into two sections

•      linea terminalis divides them

•      upper portion false pelvis

•      lower portion true

 

True Pelvis

•      pelvic inlet

•      pelvic cavity

•      pelvic outlet

Measurement of Pelvis

•      external and internal palpation

•      pelvic xray or pelvimetry

•      Ultrasound

 

Types of Pelvis

•      gynecoid -50%

•      android - 23%

•      anthropoid -24%

•      platypelloid - 3%

 

Gynecoid

•      slightly ovoid

•      transversely rounded

•      subpubic arch wide

•      side walls straight

•      vaginal spontaneous

 

Android

•      Heart shaped

•      deep

•      side walls convergent

•      narrow subpubic arch

•      C/section

•      vaginal difficult with forceps

 

Anthropoid

•      Oval wider anterior

•      straight side walls

•      narrow subpubic arch

•      forceps / spontaneous if occipitoposterior or  occipitoanterior

 

Platypelloid

•      flattened anteroposteriorly

•      wide transversely

•      straight side walls

•      wide subpubic arch

•      Not favorable for vaginal birth

 

Nature of Soft Tissues

•      uterus-

–    muscular upper section thickens -strong contractions

–    lower stretches and thins accommodate

•      cervix - soften, thin and open

•      vagina - expand to allow passage of fetus

–    hormonal changes causes increased vascularity, thickening of mucosa, relaxation of connective tissue, hypertrophy of smooth muscle

•      musculature of perineum

–    stretch and become thinner provide counter pressure for fetus

 

Fetal Considerations

•      Head

•      Attitude

•      Lie

•      Presentation

•      Position

•      Placenta

 

Head - Anatomy

•      Composed of bony parts

•      Hinder or make birth easier

•      Bones are not fused – capable of molding

•      Three major parts

–   Face

–   Cranium – base of skull

–   Vault of cranium – roof

 

Anatomy

•      Sutures

–   Frontal

–   Sagittal

–   Coronal

–   lambdoidal

•      Fontanelles

–   Anterior

–   posterior

Important Fetal Skull Landmarks

•      Mentum – chin

•      Sinciput – brow

•      Bregma – anterior fontanelle

•      Vertex – area between ant and post fontanelle

•      Occiput – beneath post fontanelle

Attitude

•      also known as habitus

•      body position or posture of fetus

•      Relation of fetal parts to one another

•      attitude of flexion

Lie

•      relationship of the cephalocaudal or long axis of the fetus to the long axis of the mother

•      fetus parallel to mother - longitudinal lie

•      fetus perpendicular - transverse lie

Presentation

•      part of the fetal body that enters the pelvis first

•      and first part to leave mothers body

•      Determined by fetal lie

•      Three types

–   Cephalic

–   Breech

–   Shoulder

 

Head –cephalic

•      Vertex

–    most common if fetus has a flexed attitude it is vertex

•      Military

–    Neither flexed or extended

•      Brow

–     extended it is brow presentation

•      Face

–    hyperextended

 

Breech

•      Complete

•      Frank

•      Footling

 

Variations of Presentation

•      RSP- Right Sacroposterior - complete breech

•      LSP -Left sacoposterior - single footling

•      LMT- left mento transverse - face presentation

•      LSA- left sacroanterior - complete breech

•      RSA- right sacroanterior - frank breech

•      RSCA ( RADA)- right scapuloanterior - transverse - shoulder presentation

Station

•      Relationship of presenting part to an imaginary line drawn between the ischial spines of maternal pelvis

•      Figure 18.7

•      Zero at the spines

•      Plus below

•      Minus above

Position

•      relationship of the presenting part of the fetus to the mothers pelvis

•      side of maternal pelvis - left or right

•      landmark of presenting part

–    O - occiput,

–     M- mentum ( face)

–     S- sacrum

–     A - acromium process (shoulder)

Position cont.

•      relative position of landmark to quadrant of maternal pelvis

•      A - anterior

•      P- posterior

•      T - transverse

•      Most common position is LOA

Forces of Labor

•      Primary

–   uterine contractions – to full dilatation

•      Secondary

–   Use of abdo. muscles to push in second stage

Primary Forces -Uterine Contractions

•      contractions of strong muscles propel intrauterine contents against soft tissue

•      intermittent with periods of relaxation

•      three phases

–     increment - building up

–     acme- peak

–    decrement- letting-up

•      characteristics - frequency, duration, intensity

Frequency

•      from the beginning of one contraction to the beginning of the next

Duration

•      beginning of the increment to the end of decrement

Intensity

•      strength of contraction at acme

•      palpation or intrauterine catheter

Secondary Forces -Ability to bear down

•      women voluntary assist during delivery

•      ready, willing and able

•      fatigue, anesthesia, concurrent medical conditions

•      assistance forceps: vacuum extraction, external Fundal pressure

Psychological Considerations

•      preparation, past experience, type and effectiveness of coping mechanisms

•      Table 18.3

What Causes Onset of Labor

•      several theories regarding onset of labor

•      progesterone withdrawal theory

•      estrogen stimulation theory

•      fetal cortical theory

•      fetal membrane phospholipid-arachidonic acid-prostaglandin theory

•      uterine distention

Progesterone Withdrawal Theory

•      progesterone metabolism in fetal membranes decreases at term

•      speculated this causes increase in prostaglandin synthesis

•      results in increased uterine contractility

Estrogen Stimulation Theory

•      estrogen irritates myometrium of uterus

•      causing prostaglandin synthesis

•      causing uterine contractility

Fetal Cortisol Theory

•      biochemical changes in fetal membranes

•      stimulates contractions and onset of labor

Fetal Membrane Phospholipid-arachidonicTheory

•      increase in prostaglandin stimulated by fetal membranes

•      irritates myometrium

•      prostaglandin found in blood and amniotic fluid

Uterine Distention

•      enlarges beyond a certain point contractions will begin

Myometrial Activity

•      True labor divides uterus

•      Division called physiologic retraction ring

•      Upper portion thickens as labor progresses

•      Lower segment is passive

•      As labor continues lower segment expands and thins out

•      Effacement and Dilatation

Mechanisms of Labor

•      effacement

•      dilation

•      station

Effacement

•      shortening and thinning of the vaginal portion of the cervix

•      long , thick 0%

•      short and thin barely distinguishable cervix  - 100%

Dilation

•      enlargement of cervical opening

Station

•      relationship of the presenting part with an imaginary line drawn between the ischial spines of mother

•      -5 to +5

•      minus above ischial - floating

•      plus below - engaged

Premonitory Signs and Symptoms of Labor

•      lightening

•      braxton hicks

•      cervical changes

•      bloody show

•      spontaneous rupture of membranes

•      weight loss

•      burst of energy

Lightening

•      known as dropping

•      fetus descends in pelvis

•      2-3 weeks before labor

•      easier breathing

•      urinary frequency

Braxton-Hicks Contractions

•      false irregular contractions

•      can occur throughout pregnancy

•      ready uterus

Cervical Changes

•      softening

•      dilates

•      thins slowly

Bloody Show

•      mucus plug dislodges

•      brownish discharge

Spontaneous Rupture of Membranes

•      rupture or a trickle

•      nitrazine paper turns blue

•      possible prolapse & infection

•      induction may be needed

Weight loss

•      1-3 pounds

•      just before onset of labor

Burst of Energy

•      nesting instinct

•      clean everything

True vs. False labor

•      onset of regular contractions with opening of cervix

Early Labor

•      mild and infrequent contractions

Cardinal Movements

•      engagement

•      descent

•      flexion

•      internal rotation to

•      extension

•      external rotation

•      expulsion

Engagement

•      Descent of presenting part past the ischial spine

Descent

•      presenting part enters the true pelvis

•      progressive downward movement of the fetus toward pelvic outlet

Flexion

•      flexion of head for narrowest portion of head to fit through

Internal Rotation

•      turning of the head to the side

Extension

•      extends to pass under the symphisis pubis

•      not to rapid descent prevent damage to maternal tissues

External Rotation

•      restitution

•      after delivery of head moves to realign with body

Expulsion

•      anterior shoulder first

•      then delivery of infant

Stages of Labor

•      four distinct stages

•      stresses for mom ad infant

•      nurse need to

–    assess client needs

–   recognize abnormal situations

–   provide appropriate nursing interventions

First stage of labor - Dilation

•      onset of true labor - complete dilation and effacement

•      primigravida- 6 - 18 hours as long as 24

•      multigravida - 2-10 as long as 14

•      3 phases - latent, active  & transition

Latent Phase

•      onset - 3 cm - 50% effaced

•      presenting part high

•      contractions short in duration lasting 15-30 seconds

•      women feelings of “not sure”  expectation, apprehensive and excited

Active Phase

•      cervix 4- 7 cm. 75% effaced

•      presenting part nears 0 station

•      3-4 minutes apart duration 45-60 seconds

•      mod to strong intensity

•      requires breathing as pain increases

•      women sure in labor & request pain medication

Transition Phase

•      dilation from 8-10 cm.

•      presenting part descents below ischial spines +1,+2 station

•      contractions 1-2 minutes and very strong

•      shortest and most intense

•      inwardly focused and sometimes lose control

Second Stage of Labor- Delivery

•      cervix fully dilated

•      few minutes to 2  hours

Third Stage of Labor - Placenta

•      begins delivery of infant and ends with delivery of placenta

•      placenta separates from uterus

•      followed by repair of episiotomy, lacerations

Fourth Stage of Labor - Recovery

•      1-4 hours following delivery

•      uterus contracts preventing hemorrhage

Physiologic Responses to Labor

•      maternal and fetal stress throughout labor , delivery and following delivery

Maternal Responses

•      Cardiovascular

•      respiratory

•      Gastrointestinal

•      Renal

•      Blood

•      Fluid and electrolytes

Cardiovascular

•      cardiac output increases

•      blood pressure elevations caused by contraction

•      increased possibility of supine hypotension

Respiratory

•      need for increased oxygen

•      Hyperventilation causes respiratory alkalosis

•      End of 1st stage mild metabolic acidosis

•      Compensated by respiratory alkalosis

•      2nd stage PaCo2 levels raise and lactate levels causing mild respiratory acidosis

•      therefore women has a metabolic acidosis uncompensated by respiratory alkalosis

Gastrointestinal

•      Motility decreased

•      Acidity of gastric contents increases

•      Aspiration an issue

•      Oral hydration primary goal

Renal

•      Increase in maternal renin, plasma renin activity and angiotension

•      Helps control utero-placental blood flow

•      Bladder pushed forward and upward

•      Some edema of tissues

Blood

•      WBC count increases to 25,000 – 30,000

•      Increase in neutrophils

•      Physiologic response to stress

•      Blood glucose levels drop because it is used as energy source

fluid /Electrolytes

•      Increased perspiration

Fetal Responses

•      physiologic changes

•      cardiac stresses

•      acidosis - respiratory and metabolic

•      Fetal movements

•      Behavior state