LaborLabor is the physiologic

process by which a fetus is expelled form the uterus to the outside world.

It involves the sequential integrated changes in the uterine decidua, and myometrium.

Changes in the uterine cervix tend to precede uterine contractions

Dilatation: the enlarging of the cervix to 10 centimeters.

Effacement: the thinning of the cervix. Your cervix starts out being two inches long, and 50% effaced would be a 1 inch

cervix.

Labor - Mechanics Uterine contractions have two major goals:

1. To dilate cervix2. To push the fetus through the birth canal

Success will depend on the three P’s:1. Powers

2. Passenger3. Passage

PowerUterine contractionsPower refers to the force

generated by the contraction of the uterine myometrium

Activity can be assessed by the simple observation by the mother, palpation of the fundus, or external tocodynamometry.

Contraction force can also be measured by direct measurement of intrauterine pressure using internal manometry or pressure transducers.

Power

There is no specific criteria for adequate uterine activity

Generally 3-5 contractions in a 10 minute period is considered adequate labor

Passenger

Passenger =fetusFetal variables that can affect labor:Fetal sizeFetal Lie – longitudinal, transverse or obliqueFetal presentation – vertex, breech, shoulder,

compound (vertex and hand), and funic (umbilical cord).

Attitude – degree of flexion or extension of the fetal head

Position Number of fetusesPresence of fetal anomalies – hydrocephalus,

sacrococcygeal teratoma

Cervical effacement and dilation

StationStation – degree of

descent of the presenting part of the fetus, measured in centimeters from the ischial spines in negative and positive numbers.

-5 is a floating baby, 0 station is said to

be engaged in the pelvis,

and +5 is crowning.

PassagePassage = PelvisConsists of the bony pelvis

and soft tissues of the birth canal (cervix, pelvic floor musculature)

Small pelvic outlet can result in cephalopelvic disproportion

Bony pelvis can be measured by pelvimetry but it not accurate and thus has been replaced by a clinical trial of labor

Passage

www.uptodate.com

The Stages of Labor

First StageInterval between the

onset of labor and full cervical dilation

Two phases:Latent phase – onset o f

labor with slow cervical dilation to ~4 cm and variable duration

Active phase – faster rate of cervical change, 1-1.2 cm /hour, regular uterine contractions

The Labor Curve

First stage - A: latent phase; B + C + D: active phase; B: acceleration; C: maximum slope of dilation; D: deceleration; E: second stage.

LaborFreidman’s

curve is a good guideline for expected progression in labor and therefore helpful to note abnormal labor patterns.

Labor NulliG MultiG

1st Stage Active phase

Duration 6-18 h 2-10 h

Dilation ~1 cm/h ~1.5 cm/h

Arrested >2 h >2h

2nd Stage 0.5-3 h 5-30 min

3rd Stage 0-30 min 0-30 min

Fig 1:  An idealized labor pattern.  The normal patterns of cervical dilation (solid line) and descent (broken line) as they are traced against elapsed time in labor. The distinctive phases of the first stage are shown. The active phase comprises the interval from the onset of the acceleration phase to the beginning of the second stage.

Labor – Second Stage Interval between full

cervical dilation to delivery of the infant.

Characterized by descent of the presenting part through the maternal pelvis and expulsion of the fetus.

Indications of second stage:

1. Increased maternal show

2. Pelvic/rectal pressure3. Mother has active role

of pushing to aid in fetal descent.

Labor – Second StageMolding is the alteration of

the fetal cranial bones to each other as a result of compressive forces of the maternal bony pelvis.

Examining the fetal head during the second stage may become difficult due to molding

Caput is the localized edematous area on the fetal scalp caused by pressure on the scalp by the cervix.

PrimiG – 0.5-3 h; mulitG 0-30min

Suctioning the nasopharynx

Clamp the umbilical cord

Cut between the clamps

Labor – Third Stage Placental separation and delivery.

The time from fetal delivery to delivery of the placenta

Signs of placental separation:

a. The uterus becomes globular in shape and firmer.

b. The uterus rises in the abdomen.

c. The umbilical cord descends three (3) inches or more further out of the vagina.

d. Sudden gush of blood.

Labor – Third StagePlacenta is delivered using

one hand on umbilical cord with gentle downward traction. Other hand on abdomen supporting the uterine fundus.

Risk factor for aggressive traction is uterine inversion.

Obstetrical emergency!!Normal duration between 0-

30 min for both PrimiG and MultiG

Inspect the placenta for completeness

AMTSL = Active management of third stage of labour. RP = retained placenta. CCT = controlled cord traction. Hb = Haemoglobin. BP = Blood pressure. MRP = Manual removal of placenta. Hb = haemoglobine.

Labor – Fourth StageRefers to the time from delivery of the

placenta to 1 hour immediately postpartumBlood pressure, uterine blood loss and pulse

rate must be monitor closely ~ 15 minutesHigh risk for postpartum hemorrhage from:Uterine atony, retained placental fragments,

unrepaired lacerations of vagina, cervix or perineum.

Occult bleeding may occur – vaginal hematoma

Be suspicious with increased heart rate, pelvic pain or decreased BP!!!!!!

Cardinal Movements of Labor

This refers to the movements made by the fetus during the first and second stage of labor. As the force of the uterine contractions stimulates effacement and dilatation of the cervix, the fetus moves toward the cervix.

When the presenting part reaches the pelvic bones, it must make adjustments to pass through the pelvis and down the birth canal

Seven distinct movements:

1.Engagement2.Descent3.Flexion4.Internal

rotation5.Extension6.External

rotation/restitution

7.Expulsion

Cardinal Movements of Labor

EngagementPassage of the widest diameter fetal presenting

part below the plane of the pelvic inletThe head is said to be engaged if the leading edge

is at the level of the ishial spines. DescentRefers to the downward passage of the presenting

part through the bony pelvisNot steady processGreatest at deceleration phase of first stage and

during 2nd stage of labor

Cardinal Movements of LaborFlexionOccurs passively as the head descends due to the

shape of the bony pelvis.Partial flexion occurs naturally but complete flexion

usually occurs only in the labor processComplete flexion places the fetal head in optimal

smallest diameter to fit through the pelvis

Internal RotationRotation of the fetal head from occiput transverse

to occiput either in anterior or posterior positionOccurs passively due to the shape of the bony

pelvis

Cardinal Movements of Labor

ExtensionOccurs when the fetus has descended to the level of

the vaginal introitusWhen occiput is just past the level of the symphysis,

the angle of the birth canal changes to upward position

External Rotation/RestitutionAs the head is delivered, it rotates back to its original

position prior to internal rotationIt aligns anatomically with the fetal torsoThe release of the passive forces on the fetal head

allows it to return to appropriate position

Expulsion

Delivery of the fetusAfter delivery of the fetal

head, descent and intraabdominal pressure by mother brings shoulder to the level of the symphysis

Downward traction allows release of the shoulder and the fetus is delivered.

Analgesia in labor Discomfort during Labor and

BirthPain and discomfort experienced during labor have

two neurologic origins: visceral and somatic Neurologic origins

Visceral pain: from cervical changes, distention of lower uterine segment, and uterine ischemia

Located over the lower portion of abdomen Referred pain: originates in uterus, radiates to abdominal wall,

lumbosacral area of back, iliac crests, gluteal area, and down the thighs

Somatic pain: pain described as intense, sharp, burning, and well localized Stretching and distention of perineal tissues and pelvic floor to

allow passage of fetus, from distention and traction on peritoneum and uterocervical supports during contractions, and from lacerations of soft tissue

Perception of pain

Threshold remarkably similar in all, regardless of gender, social, ethnic, or cultural differences

Differences play definite role in person’s perception of and behavioral responses to pain

Expression of painPain results in physiologic

effects and sensory and emotional (affective) responses

Emotional expressions of suffering often seen Increasing anxiety Writhing, crying, groaning,

gesturing (hand clenching and wringing), and excessive muscular excitability

Cultural expression of pain varies

Factors influencing pain response

Physiologic factorsCultureAnxietyPrevious experience

Childbirth preparation

Comfort and support

Environment

Distribution of labor pain A. Distribution of labor pain during first stage B. Distribution of labor pain during later

phase of first stage and early phase of second stage

C. Distribution of labor pain during later phase of second stage and during birth

(Gray shading indicates areas of mild discomfort; light-colored shading indicates areas of moderate discomfort; dark-coloredshading indicates areas of intense discomfort.)

Nonpharmacologic Managementof Discomfort

Nonpharmacologic measures often simple, safe, and inexpensive

Provide sense of control over childbirth and measures best for woman

Methods require practice for best results

Try variety of methods and seek alternatives, including pharmacologic methods, if measure used is not effective

Nonpharmacologic Managementof Discomfort

Childbirth educationDick-Read methodLamaze methodBradley method

Relaxing and breathing techniquesRelaxationImagery and visualizationMusicTouch and massageBreathing techniquesEffleurage and counterpressureWater therapy (hydrotherapy)Transcutaneous electrical nerve stimulation

Pharmacologic Managementof Discomfort

Nerve block analgesia and anesthesiaLocal perineal infiltration

anesthesia

Prudendal nerve block

Spinal anesthesia (block) Disadvantages

Medication reactions (allergy)

Hypotension

Ineffective breathing

Headache Autologous epidural blood

patch

Sedatives

Analgesia and anesthesiaAnesthesia

Systemic analgesia Opioid agonist analgesics

Opioid (narcotic) agonist–antagonist analgesics

Co-drugs

Ataractics

Opioid (narcotic) antagonists

Pain Pathways and Sites of Pain Pathways and Sites of Pharmacologic Nerve BlocksPharmacologic Nerve BlocksA. A. Pudendal block; suitable Pudendal block; suitable

during second and third stages during second and third stages of labor and for repair of of labor and for repair of episiotomyepisiotomy

B.B. Epidural block; suitable Epidural block; suitable during all stages of labor and for during all stages of labor and for repair of episiotomyrepair of episiotomy

Pain Pathways and Sites Pain Pathways and Sites of Pharmacologic Nerve of Pharmacologic Nerve

BlocksBlocksNerve block analgesia and anesthesiaEpidural anesthesia/analgesia

Lumbar epidural anesthesia/analgesia

Walking epidural analgesiaEpidural and intrathecal opioids

Membranes and spaces of spinal Membranes and spaces of spinal cord and levels of sacral, cord and levels of sacral, lumbar, and thoracic nerveslumbar, and thoracic nerves

Cross section of vertebra and Cross section of vertebra and spinal cordspinal cord

Levels of Anesthesia Necessary for Levels of Anesthesia Necessary for Cesarean and Vaginal BirthsCesarean and Vaginal Births

Cesarean birth

Vaginal birth

Care ManagementPlan of care and interventions (cont’d)

Administration of medication Intravenous route Intramuscular route Spinal nerve block

Signs of potential problemsSafety and general careAnesthesia in the obese woman

Key Points

Expected outcome of preparation for childbirth and parenting is “education for choice”

Nonpharmacologic pain and stress management strategies are valuable for managing labor discomfort alone or in combination with pharmacologic methods

Gate-control theory of pain and stress response are bases for many of the nonpharmacologic methods of pain relief

Type of analgesic or anesthetic used is determined in part by stage of labor and method of birth

Opioid effects can be potentiated with ataractics

In SummaryKnow the different stages of laborKnow the labor curveKnow the cardinal movements of laborKnow the causes of postpartum hemorrhage MD must understand medications, expected effects, potential adverse

reactions, and methods of administration Maternal fluid balance is essential during spinal and epidural nerve

blocks Maternal analgesia or anesthesia potentially affects neonatal

neurobehavioral response Use of opioid agonist-antagonist analgesics in women with preexisting

opioid dependence may cause symptoms of abstinence syndrome (opioid withdrawal)

General anesthesia rarely used for vaginal birth May be used for cesarean birth or when needed in emergency childbirth

situation

Thank you for your attention!