COURSE AND CONDUCT OF LABOR AND DELIVERY ppt

COURSE AND CONDUCT OF LABOR AND DELIVERY 153153 6 COURSE AND CONDUCT OF LABOR AND DELIVERY C H A P T E R Labor is the normal process of coordinated, effective involuntary uterine contra

COURSE AND CONDUCT OF LABOR AND DELIVERY 153

153

6

COURSE AND CONDUCT

OF LABOR AND DELIVERY

C H A P T E R

Labor is the normal process of coordinated, effective involuntary uterine contractions that lead to progressive cervical effacement and dilatation and descent and delivery of the newborn and pla- centa Near its termination, labor may be augmented by voluntary

bearing-down efforts to assist in delivery of the conceptus

False labor is characterized by irregular (both in interval and duration), brief contractions without fundal dominance, cervical change, or a lower station of the fetal vertex or breech Dilatation of the cervix is the diameter of the cervical os ex- pressed in centimenters (0–10) Effacement is cervical thinning that

occurs before and especially during first stage labor Effacement ofthe cervix is expressed as a percentage of cervical length (normally

⬃2.5 cm) (Figs 6-1, 6-2) An uneffaced cervix is 0%; one about0.25 in length is 100% effaced Effacement and dilatation are caused

by retraction (takeup) of the cervix toward the uterine corpus, not

by pressure of the presenting part

The initiation of labor in the human is poorly understood.Labor can be triggered by one or more significant endocrine orphysical changes, for example, abdominal trauma The onset of la-bor can occur at any time after well-established pregnancy, but thelikelihood increases as term is approached Labor can be induced

or stimulated (augmented) by oxytocic agents (e.g., oxytocin orprostaglandin E2) (Fig 6-3)

In⬃10% of gravidas, the fetal membranes rupture before the onset of labor This reduces the capacity of the uterus, thickens the

uterine wall, and increases uterine irritability Labor usually follows

At term, 90% will be in labor within 24 h after membrane rupture.

If labor does not begin in 24 h, the case must be considered plicated by prolonged rupture of the membranes

com-Immediately before or early in labor, a small amount of

red-tinged mucus may be passed (bloody show or mucous plug) This

is a collection of thick cervical mucus often mixed with blood and

154 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

is evidence of cervical dilatation and effacement and, frequently,descent of the presenting part

The beginning of true labor is marked by increasingly frequent, forceful, prolonged, and, finally, regular uterine contractions Low backache may precede or accompany the uterine contractions

(pains) Each contraction starts with a gradual buildup of intensity,and a similar dissipation follows the peak Normally, the contrac-tion will be at its height before discomfort is felt Dilatation of thelower birth canal almost always will cause deep pelvic or perinealpain Nonetheless, occasional nulliparas and some multiparas mayhave a brief, virtually pain-free labor

Labor entails the interaction of the so-called 4Ps

● The passenger (the fetal size, presentation, position)

● The pelvis (size and shape)

● The powers (effective forces of labor, e.g., uterine contractions)

● The placenta (an obstruction if implanted low in the

uterus)

FIGURE 6-1. Dilatation and effacement of the cervix in a primipara

FIGURE 6-3. Production of prostaglandins in human parturition.

(Modified after Liggins.) (From M.L Pernoll and R.C Benson, eds Current Obstetric &

Gynecologic Diagnosis & Treatment, 6th ed Lange, 1987.)

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156 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

Each of these factors, alone or in combination, can make for anormal or a complicated labor and delivery For example, if the fe-tus is large and the pelvis is small, labor may be prolonged orprogress may be impossible despite strong contractions, even with

a placenta normally implanted in the fundus

NORMAL LABOR

Since, hopefully, the end result of labor is the vaginal delivery ofthe fetus, membranes, and placenta, the method of judging its

progress is based on assessments toward that end The first stage

of labor begins with the onset of labor and ends with complete

FIGURE 6-4. Relationship between cervical dilatation and descent of the presenting part in a primipara L, latent phase; A, acceleration phase; M, phase

of maximum slope; D, deceleration phase; and 2, second stage

(From M.L Pernoll and R.C Benson, eds Current Obstetric & Gynecologic Diagnosis

(10 cm) dilatation of the cervix The first stage is the longest, averaging 8–12 h for primigravidas or 6–8 h for multiparas How-

ever, the first stage of labor may be markedly shorter or longer pending on the 4Ps

de-Labor is a very dynamic process, and contractions should crease steadily in regularity, intensity, and duration This is not al-

in-ways the case, and one must set limits concerning the progress oflabor (Figs 6-4, 6-5)

It is useful to divide the first stage of labor into two phases Thus, the latent phase of labor begins with the onset of regular uter- ine contractions and extends to the start of the active phase of cer- vical dilatation (⬃3–4 cm)

COURSE AND CONDUCT OF LABOR AND DELIVERY 157

FIGURE 6-5. Composite mean curves for descent (solid line) and tion (broken line) for 389 multiparas L, latent phase; A, acceleration phase;

dilata-M, phase of maximum slope; D, deceleration phase; and 2, second stage lationship is shown between acceleration period of descent and maximum slope of dilatation (shaded area), between latent period of descent and latent plus acceleration phases of dilatation, and between maximum slope of de- scent and deceleration plase plus second stage.

Re-158 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

The second stage of labor begins when the cervix becomes fully dilated and ends with the complete birth of the infant The second stage normally lasts ,30 min While one should be concerned when

the second stage extends longer than 1 h (based on fetal morbidityand mortality) Safety for the fetus may be assured by thoughtfulmonitoring

The third, or placental, stage of labor is the period from birth

of the infant to 1 h after delivery of the placenta The rapidity ofseparation and means of recovery of the placenta determine the du-ration of the third stage (Fig 6-6)

MANAGEMENT OF THE FIRST STAGE

OF LABOR INITIAL EXAMINATION

AND PROCEDURES

● Obtain a history of relevant medical details following the

last examination

FIGURE 6-6. Major types of deviation from normal progress of labor may

be detected by noting dilatation of the cervix at various intervals after labor begins.

(From K.P Russell In: R.C Benson, ed Current Obstetric & Gynecologic Diagnosis &

Treatment, 4th ed Lange, 1982.)

COURSE AND CONDUCT OF LABOR AND DELIVERY 159

● Record the patient’s vital signs (temperature, pulse, and BP).

Examine a clean-catch urine specimen for proteinuria andglycosuria

● Do a brief general physical examination.

● Palpate the uterus to determine the fetal presentation, position, and engagement (Leopold’s maneuvers) (Fig 6-7) Auscultate the fetal heartbeat, and mark the skin where the heartbeat is

FIGURE 6-7. Leopold’s maneuvers Determining fetal presentation (A and

160 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

loudest to note the shift and descent of the point of maximalintensity with progressive labor This is evidence of internalrotation and descent of the fetus (the mechanism of labor)

● Note the frequency, regularity, intensity, and duration of uterine contractions and the myometrial tone with and be-

tween contractions Observe the patient’s reactions and hertolerance of labor Restlessness and discomfort often de-velop as labor progresses

● Check for vaginal bleeding or leakage of amniotic fluid.

Nitrazine indicator paper will turn from green to yellowwhen moistened with amniotic fluid (pH 7.0) Other testsmay be used in doubtful cases

● Examine the patient vaginally and record both the time and

results of the examination Use a surgically clean glove

Identify the fetal presenting part and its station in tion to the level of the ischial spines Station is the level

rela-of the head or breech in the pelvis If the presenting part

is at the spines, it is said to be at “zero station.” If abovethe spines, the distance is stated in minus figures (1 cm,

2 cm, 3 cm, and “floating”) If below the spines, thedistance is noted in plus figures (1 cm, 2 cm, 3 cm,and “on the perineum”) (Fig 6-8) When the most inferior

part of the head is at the level of the ischial spines, thestation is zero

Station zero is assumed by projection to be actualengagement, that is, the biparietal diameter at the level

of the inlet However, with considerable molding, caputsuccedaneum, or a sincipital presentation of the head,the biparietal diameter may be a significant distanceabove the inlet even though the tip of the vertex is at thespines without true engagement

Dilatation of the cervix by direct palpation is expressed

as the diameter of the cervical opening in centimeters

A diameter of 10 cm constitutes full dilatation Effacement of the cervix (process of thinning out) may occur before labor in the nulligravida but is less likely before the first stage of labor in the multigravida

The position of the presenting part usually can be firmed by internal examination

con-Vertex presentations (Fig 6-9) The fontanelles and the

sagittal suture are palpated The position is determined

by the relation of the fetal occiput to the mother’s right

or left side This is expressed as OA (occiput directlyanterior), LOA (left occiput anterior), LOP (left occiputposterior), and so on

Breech presentations are determined by the position of the infant’s sacrum in relation to the mother’s right or

left side This is expressed as SA (sacrum directly rior), LSA (left sacrum anterior), LSP (left sacrum pos-terior), and so on

ante-Face presentation is caused by extension of the fetal head on the neck The chin, a prominent and identifiable

facial landmark, is used as the point of reference Aswith vertex presentations, the position of the fetal chin

is related to the anterior or posterior portion of the left

or right side of the mother’s pelvis This is expressed asRMP (right mentum posterior) and so on

Brow, bregma, and sinciput presentations are

presenta-tions midway between flexion and extension These ally are temporary attitudes that convert during labor toface or occiput presentation

usu-Transverse presentations occur when the long axis of the

fetal body is perpendicular to that of the mother Oneshoulder (acromion) will occupy the superior strait, but

it will be considerably to the right or left of the midline

Transverse presentations are designated by relating the infant’s inferior shoulder and back to the mother’s back

COURSE AND CONDUCT OF LABOR AND DELIVERY 161

FIGURE 6-9.

162

or abdominal wall Thus, LADP (left

acromiodorsopos-terior) means that the infant’s lower shoulder is to themother’s left, and its back is toward her back

Compound presentations, caused by prolapse of a hand,

arm, foot, or leg, are complications of one of the otherpresentations These unusual presentations generally are

recorded descriptively without abbreviations

PREPARATION OF THE PATIENT

FOR LABOR

Following the initial internal examination, the following may bereasonable:

Ambulation, within reasonable limits, may add to the patient’s

comfort However, keep the patient in bed after the membranes haveruptured or until the presenting part has engaged to avoid cord pro-lapse or compression

Allow only clear liquids by mouth during labor to avoid

dehy-dration

Analgesia should not be given until labor is definitely lished with the cervix
3 cm dilated Analgesics and anesthesiamust be ordered on an individual basis, considering each patient’sobstetric problems, the quality of labor, and her desire to be alert

estab-or subdued

FURTHER EXAMINATIONS

AND PROCEDURES

Electronic fetal monitoring (EFM) is simply one of the means of

assessing fetal status It does have the advantage of being ous The external type is innocuous, and the internal type carriesonly slight risk Although EFM is an excellent diagnostic tool, it isnot a substitute for correct clinical judgment Current retrospectiveand prospective data support the use of continuous internal EFMfor high-risk obstetric patients Internal EFM is preferable to ex-ternal EFM because it is more precise and comprehensive in ap-praising fetal status Nonetheless, electronic monitoring of low-riskobstetric patients has not demonstrated a beneficial cost–benefitratio

continu-If continuous EFM is not used, auscultate and record the fetalheart tones (FHT) for 1 min following a uterine contraction at leastevery 30 min during the first stage, at least every 5 min duringthe second stage, when the membranes rupture and again within

COURSE AND CONDUCT OF LABOR AND DELIVERY 163

164 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

30 min after the rupture, and every 5 min or more often as cated if complications develop or if meconium passes in vertexpresentation

indi-Perform external and internal examinations as often as sary to determine the progress of the labor Descent and internal ro-

neces-tation of the fetus often can be determined by external palpationalone Too frequent vaginal or rectal examinations cause the patientdiscomfort and increase the incidence of intrauterine infection, par-ticularly after rupture of the membranes

Figure 6-6 details normal and abnormal labor curves for both nulliparas and multiparas as determined by measuring cervical

dilatation as a function of time The abnormal labor patterns are

quantified in Chapter 7 Encourage the patient to void frequently.

Palpate the abdomen occasionally for signs of bladder fullness.Catheterize if involuntary distention occurs or if voiding is obvi-ously inadequate

DELIVERY: MANAGEMENT OF THE

NORMAL SECOND STAGE OF LABOR VERTEX DELIVERY (TABLES 6-1, 6-2)

Final preparation for delivery should be completed by the time thepresenting part reaches the pelvic floor, or sooner if labor is pro-gressing very rapidly

Spontaneous delivery of the infant presenting by the vertex is

divided into three phases: (1) delivery of the head, (2) delivery of the shoulders, and (3) delivery of the body and legs

Preparation for Delivery

● Place the patient in a modified lithotomy position for

deliv-ery The left lateral decubitus (Sims) or squatting positionmay be used if a spontaneous uncomplicated birth is antic-ipated Another alternative is the squatting position

● The physician and assistants must carefully scrub their hands and wear masks, eye protection, and sterile gloves Any de-

livery may become surgically complicated

● Administer anesthesia if necessary (e.g., pudendal block)

● Cleanse the pudendum with water and surgical detergent

● Drape the patient with sterile towels or sheets or both

● Sterile instruments and necessary supplies should be arrangedconveniently on a table or stand

(Extensionoccurs inbrow and facepresentations)

Depends onpelvicarchitectureand cephal-opelvicrelation-shipsDescent isusuallyslowlyprogressive

Takes place duringdescent Afterengagement,vertex usuallyrotates to thetransverse It mustnext rotate to theanterior orposterior to passthe ischial spines,whereupon, whenthe vertex reachesthe perineum,rotation from aposterior to ananterior positiongenerally follows

Followsdistention

of the perineum

by thevertex

Headconcomit-antly stemsbeneath thesymphysis

Extension

is completewithdelivery ofhead

Following delivery,head normallyrotates to theposition it originallyoccupied atengagement Next,the shouldersdescend in a pathsimilar to thattraced by the head.The shoulders rotateanteroposteriorlyfor delivery Thenthe head swingsback to its position

at birth The body

of the infant isdelivered next

TABLE 6-1

MECHANISMS OF LABOR: VERTEX PRESENTATION

External RotationEngagement Flexion Descent Internal Rotation Extension or Restitution

TABLE 6-2

MECHANISMS OF LABOR: FRANK BREECH PRESENTATION

Lateral External Rotation

Gradual descent

is the rule

Ordinarily takes placewhen breechreaches levatormusculature Fetalbitrochantericrotates to APdiameter

Anterior shoulderrotates so as tobring shoulders into

AP diameter ofoutlet

Occurs whenanterior hipstems beneathsymphysis;

posterior hip

is born first

Anteriorshoulder atsymphysis,and posteriorshoulder isdelivered first(when body issupported)

After birth ofbreech andlegs, infant’sbody turnstowardmother’s side

to which itsback wasdirected atengagement ofshoulders

Head: Engages in the

chin arrests beneath

symphysis, and head

is born by gradual

flexion

Follows theshoulders

Occiput (if aposterior) or face(if an occiputanterior) rotates tohollow of sacrum;this bringspresenting part to

AP diameter ofoutlet

168 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

● Gloves (and gown) must be changed if contamination

occurs

Delivery of the Head (Figs 6-10 through 6-14)

● During the late second stage, the head distends toward theperineum and vulva with each uterine contraction, normallyaided by voluntary efforts of the mother A patch of scalpbecomes visible The presenting part recedes slightly during

the intervals of relaxation, but it crowns when its widest

FIGURE 6-10. Engagement of LOA.

FIGURE 6-13. Extension of head.

FIGURE 6-14. External rotation of head.

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170 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

portion (biparietal diameter) distends the vulva just beforeemerging

● Do not hasten delivery, lest serious damage to the mother

or child occur Control the speed of delivery by pressureapplied laterally beneath the symphysis as necessary to avoidpudendal laceration or unexpected extrusion of the infant’shead Sudden marked variations in intracranial pressure may

cause intracranial hemorrhage As the head advances, trol its progress and maintain flexion of the head by pres-

con-sure over the perineum

Draw the perineum downward to allow the head to clear the perineal body Pressure applied from the coccygeal re- gion upward (modified Ritgen maneuver) will extend the

head at the proper time and thereby protect the perineumfrom laceration

● If episiotomy is elected, it should be performed when the tal head begins to distend the introitus.

fe-● In vertex presentations, the forehead soon appears, then theface and chin, and finally the neck

● The cord encircles the neck in about 20% of deliveries Note

the number of loops If the nuchal cord is tight, attempt togently slip the loop(s) of cord over the head If this cannot

be done easily and if this is a singleton, doubly clamp thecord, cut between the forceps, and proceed with the deliv-ery Wipe fluid from the nose and mouth, then aspirate thenasal and oropharyngeal passages with a soft rubber suctionbulb or with a small catheter attached to a deLee-type suc-tion trap

● Before external rotation (restitution), which occurs next, the

head usually is drawn back toward the perineum This ment precedes engagement of the shoulders, which are nowentering the pelvic inlet

move-● From this point on, support the infant manually and tate the mechanism of labor.

facili-Do not hurry! If strong contractions wane, be patient—labor will resume Once the airway is clear, the infant can breathe and is not in jeopardy.

Delivery of the Shoulders

Caution: Never exert pressure or strong anterior or posterior tion on the head, neck, or shoulders Do not hook a finger into the child’s axilla to deliver a shoulder These maneuvers may result in

trac-a brtrac-achitrac-al plexus injury (Erb or Duchenne), trac-a hemtrac-atomtrac-a of the neck,

or a shoulder injury

● Delivery of the shoulders should be deliberate The

shoul-ders must rotate (or be rotated) to the anteroposterior eter of the outlet for delivery

diam-● Gently depress the head toward the mother’s coccyx until the anterior shoulder impinges against the symphysis Then lift the head upward This aids delivery of the posterior shoulder.

● The anterior shoulder is next delivered from behind the physis by gentle downward traction The index and third fin-ger should greatly exert pressure on the rami of the mandiblewhile the opposite index and third finger exert equal and gen-tle pressure on the occiput (Occasionally, it may be easier todeliver the anterior shoulder first.) Slipping several fingersinto the vagina at this point to assist in delivering the poste-rior arm is desirable, but undue pressure must be avoided!

sym-● In vertex presentations, a hand may present after the head.Merely sweep the infant’s hand and arm over its face, drawthe arm out, and deliver the other shoulder as outlinedpreviously

Delivery of the Body and Extremities

The infant’s body and legs should be delivered gradually by easy traction after the shoulders have been freed

IMMEDIATE CARE OF THE INFANT

● As soon as the infant is delivered, hold it with the head ered (no more than 15 degrees) to drain fluid and mucus from the oropharynx A mucus trap catheter or comparable suction device is useful in clearing the air passages If the

low-baby is below the level of the placental insertion, bloodwill drain from the placenta and cord to the newborn Thiswill amount to 30–90 mL before the cord is clamped or theplacenta separates The excess blood may benefit someneonates (e.g., isoimmunized anemic infants) and harm oth-ers (e.g., a plethoric twin)

Placing the newborn on the mother’s abdomen beforecord pulsations cease has the potential disadvantage that theinfant is not secure there and blood drains from the infant

to the placenta (usually undesirable)

● Evaluate and resuscitate if necessary (Chapter 8) (Fig 6-15)

● Clamp and cut the cord when it ceases to pulsate (or sooner

if the infant is premature or in distress, or if

isoimmuniza-COURSE AND CONDUCT OF LABOR AND DELIVERY 171

172 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

FIGURE 6-15. Resuscitation of the newborn.

tion is probable) Examine the umbilical cord for the

nor-mal two arteries and one vein Apply a sterile cord clamp,

cord tie of umbilical tape, or rubber band distal to the skinedge at the cord insertion at the umbilicus Dress the cordstump with dry gauze

● The newborn should be received into warm clean towels or blankets, and avoid chilling Apply means of identification

protec-● Examine the infant and record Apgar scores, weight, total

length, crown-rump length, shoulder circumference, cumference of the head, and cranial diameters Note facial,peripheral, genital, or other abnormalities (Chapter 8)

cir-IMMEDIATE CARE OF THE MOTHER

● Carefully inspect the perineum, vagina, and cervix for erations, hematomas, or extension of the episiotomy Iden-

lac-tify sulcus lacerations, urethral and cervical injury, and otherinjuries Lacerations of the birth canal may be described bytheir extent (expressed as first to fourth degree)

In first degree lacerations, only the mucosa or skin or

both are damaged Bleeding usually is minimal

Second degree lacerations include tears of the mucosa

or skin or both plus disruption of the superficial fasciaand the transverse perineal muscle (The anal sphincter isspared.) Bleeding often is brisk

Third degree lacerations involve the structures indicated

in second degree lacerations plus the anal sphincter Expectmoderate blood loss

Fourth degree lacerations include the structures

in-cluded in third degree lacerations and entry into the rectallumen Bleeding may be profuse, and fecal soiling is in-evitable

● Control blood loss and repair second to fourth degreelacerations

MANAGEMENT OF THE THIRD

STAGE OF LABOR AVOID INTERFERENCE IF

AT ALL POSSIBLE!

COURSE AND CONDUCT OF LABOR AND DELIVERY 173

174 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

Avoid traction on the cord before placental separation and do not knead the fundus to separate the placenta (Credé maneuver) The

former may lead to cord laceration and the latter to hemorrhage,uterine inversion, and shock Maternal morbidity and mortality ratesincrease with gross blood loss A uterus that contracts and remainscontracted rarely bleeds excessively

SEPARATION OF THE PLACENTA

The placenta is attached to the uterine wall only by anchoring villiand thin-walled blood vessels, all of which eventually tear In someinstances, the placental margin separates first In others, when the central portion of the placenta is initially freed bleeding fromthe retroplacental sinuses may assist placental separation Incom-plete separation, usually due to ineffectual uterine contractions, mayallow the retroplacental blood sinuses to remain open, so that se-vere blood loss may result

Normal placental separation is manifested first by a firmly tracting, rising fundus The uterus becomes smaller and changes in shape from discoid to globular The umbilical cord becomes longer

con-as the placenta descends There is a palpable and visible

promi-nence above the symphysis (if the bladder is empty) and a slight gush of blood from the vagina These signs normally appear within

about 3–4 min after delivery of the infant The placenta should ent at the internal os after four or five firm uterine contractions,whereupon it is expressed into the vagina for delivery

pres-These signs often are confused with other conditions: uterineanomaly, a second undelivered infant, feces, a tumor, and lacera-tions of the birth canal

RECOVERY OF THE PLACENTA

Spontaneous Uterine Expulsion of Placenta

When the uterus is firmly contracted, the mother who has not been

anesthetized may be able to bear down during a contraction to pel the separated placenta Although of historic but little clinical

ex-significance, a recording of the placenta presenting with the fetalsurface to the introitus (Schultz) or the maternal surface (Duncan)may be made Spontaneous delivery of the placenta usually is ac-complished without difficulty If it does not occur, however, the fol-lowing techniques may be used

Brandt-Andrews Technique (Modified) (Fig 6-16)

COURSE AND CONDUCT OF LABOR AND DELIVERY 175

FIGURE 6-16. Brandt-Andrews maneuver (A) Traction is extended on the cord as the uterus is elevated gently (B) Pressure is exerted between the sym- physis and the uterine fundus, forcing the uterus upward and the placenta outward, as traction on the cord is continued.

(From R.C Benson, ed Current Obstetric & Gynecologic Diagnosis & Treatment, 4th