Tài liệu Obstetrics and Gynecology Clinics of North America32 (2005) ppt

For example, internal rotation is known to occur when the fetal head descends to the level of the pelvic floor, resulting in 95% of vertex infants delivering in the most favorable occipu

Management of First and Second Stages

of Labor

Suneet P Chauhan, MD Guest Editor

For both patient and the practitioner, few things are as dramatic and ing as childbirth After months of anticipation and careful antepartum care, labor

reward-is the last phase of pregnancy in which prudent decreward-isions can improve come With over 130 million births in the world, 4 million of which occur in theUnited States, it is imperative that the clinicians are current on the recent de-velopments of intrapartum management This collection of 13 articles, written byclinicians, researchers, academicians, and private practitioners, updates the man-agement of the first, second, and third stages of labor The book is intended formedical students, labor and delivery nurses, residents, midwives, and obstetri-cians who try to optimize the outcome of each delivery

out-The first two articles describe the mechanisms of normal labor and withabnormal presentations The next three provide clinically relevant information oninduction, abnormalities of stages I and II, and active management of labor Thesixth article focuses on analgesia and anesthesia We intentionally devoted twoarticles to intrapartum assessment of the fetus to provide different perspectives

on a very important issue Intrapartum complications—chorioamnionitis, reassuring fetal heart rate tracing, and shoulder dystocia—are discussed, and theirmanagement is described in the ninth, tenth, and eleventh articles The last twoarticles concern episiotomy and management of the third stage of labor

non-0889-8545/05/$ – see front matter D 2005 Elsevier Inc All rights reserved.

32 (2005) xiii – xiv

Though obvious, it is worth acknowledging the hours of scholarly work bythe authors of the articles, and the considerable support by Carin Davis andthe staff at Elsevier is refreshing.

Suneet P Chauhan, MDDivision of Maternal–Fetal MedicineSpartanburg Regional Medical Center

101 East Wood StreetSpartanburg, SC 29303, USAE-mail address: schauhan@srhs.com

Normal Labor: Mechanism and Duration John B Liao, MD, Catalin S Buhimschi, MD,

under-of the last normal menstrual period The period from 37.0 weeks (259 days) to42.0 weeks (294 days) of gestation is regarded as ‘‘term.’’ This article focuses onthe onset, progress, and mechanics of normal labor at term Topics such aspreterm labor (labor before 37 weeks), postterm labor (labor after 42 weeks), andabnormal labor and delivery have not been addressed and are discussed in detailelsewhere in this issue

Diagnosis

Labor is a clinical diagnosis characterized by regular, painful uterine tractions that increase in frequency and intensity are associated with progressivecervical effacement or dilatation More specifically, it is associated with a change

con-in the myometrial contractility pattern from irregular ‘‘contractures’’ lasting, low-frequency activity) to regular ‘‘contractions’’ (high-intensity, high-

in the absence of cervical change are not sufficient to make the diagnosis Abloody mucous discharge (‘‘show’’) may precede the onset of labor by several

0889-8545/05/$ – see front matter D 2005 Elsevier Inc All rights reserved.

days but is not a prerequisite for the diagnosis In normal labor at term, thereseems to be a time-dependent relationship between these elements: thebiochemical connective tissue changes in the cervix usually precede uterinecontractions, which, in turn, precede cervical dilatation The fetal membranestypically rupture during the course of labor Occasionally, however, the mem-branes may rupture with leakage of amniotic fluid before the onset of labor.

The onset of labor

Labor at term may best be regarded physiologically as an event initiated bythe removal of the inhibitory effects of pregnancy on the myometrium rather than

studies have shown that quiescent myometrium obtained from term uteri andplaced in an isotonic solution contract vigorously and spontaneously without

im-portant[4]

For the purposes of considering how uterine activity is regulated during thelatter part of pregnancy and labor, four distinct physiologic phases are de-

functional quiescence (Phase 0) through the integrated action of one or more of

a series of inhibitors, including progesterone, prostacyclin, relaxin, nitric oxide,parathyroid hormone-related peptide, calcitonin gene-related peptide, adrenome-dullin, and vasoactive intestinal peptide Before term, the uterus undergoes aprocess of activation (Phase 1) and stimulation (Phase 2) Activation is broughtabout in response to one or more uterotropins (such as estrogen) with increasedexpression of a series of contraction-associated proteins (including myometrialreceptors for prostaglandins and oxytocin), functional activation of select ion

Fig 1 Regulation of uterine activity during pregnancy and labor (Adapted from Challis JRG, Gibb W Control of parturition Prenat Neonat Med 1996;1:283; Taylor and Francis Ltd http:// www.tandf.co.uk/journals ; with permission.)

channels, and an increase in connexin-43 (a key component of gap junctions).After activation, the ‘‘primed’’ uterus can be acted upon by uterotonins, such as

contract Because no single factor has been shown to be primarily responsible, it

is more accurate to refer to factors that promote rather than initiate the onset oflabor Phase 3 events (uterine involution) occur after delivery and are mediatedprimarily by oxytocin and possibly thrombin

The endocrine control of labor

Considerable evidence suggests that the fetus is in control of the timing oflabor Around the time of Hippocrates, it was believed that the reason the fetuspresented head first was so that it could kick its legs up against the fundus ofthe uterus and propel itself through the birth canal Although we have movedaway from this simple and mechanical concept of labor, the idea that the fetusplays a central role in the initiation of labor remains and has been supported by

experiments with horses and donkeys in the 1950s, for example, demonstrated agestational length intermediate between those of the parent species, whichsuggested a critical role for the fetal genotype in determining the onset of labor

the mechanism by which the fetus triggers labor at term has been elucidatedelegantly and involves glucocorticoid-mediated activation of a placental enzyme,17a-hydroxylase/17,20-lyase, which catalyzes the conversion of progesterone toestradiol-17b This switch in the progesterone:estrogen ratio leads to uterine

protein-A from the lungs into the amniotic fluid at the end of pregnancy has been

Unfortunately, there is as yet insufficient evidence to suggest that any of thesefactors are critical for the onset of labor in humans For example, the humanplacenta does not contain glucocorticoid-inducible 17a-hydroxylase/17,20-lyase

involved in the process of labor in the human reflects in large part the difficulty

in extrapolating from the endocrine control mechanisms in various animal models

to the paracrine/autocrine nature of parturition in women—processes that inhumans preclude direct investigation

Although the precise signal varies, the final common pathway toward laborseems to be activation of the fetal hypothalamic-pituitary-adrenal axis and isprobably common in all viviparous species In humans, activation of the fetalhypothalamic-pituitary-adrenal axis results in the release of C-19 steroid (dehy-droepiandrostenedione), which serves as an essential precursor for placental

but not estrogen itself—is capable of inducing preterm labor in pregnant rhesus

blocks this effect[14], which demonstrates that conversion of this precursor toestrogen at the level of the fetoplacental unit is critical for the onset of labor.Regardless of whether the signal for labor begins with the mother or the fetus,the final common pathway for labor ends in the maternal tissues of the uterusand is characterized by the development of regular phasic uterine contractions.

As in other smooth muscles, myometrial contractions are mediated through theATP-dependent binding of myosin to actin In contrast to vascular smoothmuscle, however, myometrial cells have a sparse innervation that is further

the uterus is largely humoral and depends on intrinsic factors within myometrial

con-tractile one comes through the recruitment and communication of myometrial

thereby establishing electrical synchrony within the myometrium and allowing

junctions, mRNA for connexin-43, has been shown to increase with the onset oflabor[17]

responsible, at term, for the removal of mechanisms that maintain uterinequiescence and the recruitment of factors that act to promote uterine activity Insuch a model, pathways in the fetus, placenta, and mother are interconnected

at many levels and require sequential recruitment, which allows for a level ofredundancy that can, by design, prevent a single derangement from preventing

individual paracrine/autocrine pathways implicated in the process of labor has

physiologic event that involves an integrated set of changes within the maternaltissues of the uterus (ie, myometrium, decidua, and uterine cervix) that occur

Fig 2 Electron micrograph of gap junction between myometrial cells (From Buhimschi CS, et al Forces of labor Fetal and Maternal Medicine Review 2003;14(4):273–307; with permission.)

16-OH DHEAS from fetal adrenal

17 α hydroxylase/

17,20-desmolase

dehydroandrostenedione

? - ve feedback loop

placental vasodilation

LABOR

inhibited by progestrone acting through glucocorticoid receptors

+

+ -

placental PGE2

utero-+ +

gradually over a period of days to weeks Such changes include, but are notlimited to, an increase in prostaglandin synthesis and release within the uterus,

an increase in myometrial gap junction formation, and upregulation ofmyometrial oxytocin receptors When the myometrium and cervix have beenprepared appropriately, endocrine or paracrine/autocrine factors from thefetoplacental unit bring about a switch in the pattern of myometrial activityfrom contractures to contractions (uterine stimulation) The fetus may coordinatethis switch in myometrial activity through its influence on placental steroidhormone production, through mechanical distention (stretch) of the uterus, andthrough secretion of neurohypophyseal hormones and other stimulators ofprostaglandin synthesis

Mechanics of normal labor

Uterine contractions have two major functions: to dilate the cervix and to pushthe fetus through the birth canal The fetus is not merely the passive recipient ofthese forces, however The ability of the fetus to negotiate the pelvis successfullydepends on the complex interaction of three variables: the powers, the passenger,and the passage

Powers

Powers refer to the force generated by the uterine musculature duringcontractions It is generally believed that the more optimal the powers, the morelikely a successful outcome No data exist to support this statement, however Thefeatures used to describe contractions are frequency, intensity, and duration Itshould be noted that the frequency of contractions does not necessarily reflect theforce of contraction

As with other types of muscle contractions, action potentials must begenerated and propagated to yield effective contractions in a process known

myometrial cells relies on the rapid shifts of ions through membrane ion channels[21,22], the most important of which seem to be calcium and potassium channels[23–26] Autonomous pacemaker cells in the uterus that have a higher restingpotential than other muscle cells can initiate action potentials spontaneously[27].Action potentials in the uterus occur in bursts, and the strength of contractionsrelies on their frequency and duration This, in turn, determines the number ofmyometrial cells recruited for action In this way, the electrical activity istranslated in mechanical forces exerted on the contents of the uterus in a

of labor, with early labor contractions having a peak intensity from +25 to+30 mm Hg, which increases to +60 to +65 mm Hg in the second stage of labor

[16] Other variables that may influence the strength of the contractions includeparity, the condition of the cervix, exogenous oxytocin administration, and painmedication (including epidural analgesia).

Uterine activity can be assessed qualitatively by simple observation of themother and palpation of the fundus of the uterus through the abdomen or byexternal tocodynamometry External tocodynamometry is noninvasive andrequires little expertise to measure and interpret It measures uterine contractionindirectly through changes in the shape of the abdominal wall and, as such,cannot accurately determine basal intrauterine tone Uterine activity also can bemeasured quantitatively by direct measurement of intrauterine pressure viainternal manometry or pressure transducers Placement of an intrauterine pressurecatheter allows for objective measurement of uterine activity It is invasive, canonly be performed after rupture of the fetal membranes, and has been associatedwith uterine injury (perforation) and an increased incidence of intrauterineinfection, however Montevideo units (calculated by multiplying the average peakstrength of contractions in mm Hg by the number of contractions in 10 minutes)

is the most widely used calculation for measuring the strength of uterine

investigators have proposed using an integrated formula that uses the area under

Fig 4 Uterine electrical activity recorded from two distinct sites S1 and S2, noninvasively from the abdominal surface During active labor, electrical bursts become synchronous with uterine pressure elevations, as measured by an intrauterine pressure catheter (From Buhimschi CS, et al Forces of labor Fetal and Maternal Medicine Review 2003;14(4):273–307; with permission.)

the contraction curve[30,31] No evidence exists that one method is significantlybetter than another[32].

Despite technologic improvements, the criteria for adequate uterine activityduring labor are unclear Classically, the occurrence of three to five contractions

in 10 minutes has been used to define adequate labor and is seen in approximately

In one retrospective series, 91% of women in spontaneous active labor achievedcontractile activity more than 200 Montevideo units, and 40% reached

achieving this level of uterine contractility makes a clinician more confident of

a successful labor, it is no guarantee of a successful vaginal delivery Adequatecontractions in the face of other unfavorable factors (such as malposition) still

Passenger

The passenger is the fetus Several fetal variables may influence the course ofnormal labor and delivery

Obstetricians and Gynecologists as an estimated fetal weight (not birth

risk of cesarean delivery because of cephalopelvic disproportion ment of estimated fetal weight can be made either by clinical examination(Leopold’s maneuvers) or ultrasound, although both approaches are subject

Assess-to significant errors (approximately 15%–20% at term)

longitudi-nal axis of the uterus and can be longitudilongitudi-nal, transverse, or oblique For asingle gestation, a vaginal delivery should be attempted only if the lie

is longitudinal

 Presentation Fetal presentation refers to the fetal part that directly overliesthe pelvic inlet With a longitudinal lie, presentation is usually cephalic(vertex), breech, or shoulder When more than one fetal part presents atthe pelvic inlet, the term ‘‘compound presentation’’ is used Rarely, theumbilical cord may present at the inlet, which is known as a funic pre-sentation Approximately 5% of singleton pregnancies at term have amalpresentation in labor

fetal head in relation to the fetal spine Adequate flexion (chin to chest) isnecessary to achieve the smallest possible presenting diameter in a cephalicpresentation Deflexion in the early stages of labor may be corrected by thearchitecture of the pelvic floor and uterine contractions

fetal presenting part to a denominating location on the maternal pelvis

(Fig 5) For example, in a cephalic presentation, the fetal site used forreference is typically the occiput (eg, right occiput anterior) In a breechpresentation, the sacrum is used as the designated fetal site (eg, right sacrumanterior) Any fetal position that is not right occiput, occiput anterior, or leftocciput anterior is referred to as a malposition.

presenting part of the fetus has descended into the maternal pelvis relative tothe ischial spines It is typically assessed clinically by bimanual examina-tion An older arbitrary system ( 3 to +3, with 0 being at the level of theischial spines) has been replaced with a more recent classification designed

to quantify the distance from the ischial spines ( 3 to +5 cm)

The passage through which the fetus must pass during normal labor anddelivery consists of the bony pelvis and the soft tissues of the birth canal(ie, cervix, pelvic floor musculature), both of which offer varying degrees ofresistance to fetal expulsion

The bony pelvis is comprised of the greater and lesser pelvis and is divided

by the pelvic brim Its anatomic boundaries are made up of the sacral tory, the anterior ala of the sacrum, the arcuate line of the ilium, the pectineal line

promon-of the pubis, and the symphysis pubis The true pelvis can be divided into planesthat must be navigated by the fetus during labor, including the pelvic inlet,midcavity, and outlet The female pelvis is classically described as having one

of four shapes: gynecoid, anthropoid, android, and platypoid This classificationwas designed to separate the more favorable configurations for successful vaginal

however, the shape of the female pelvis reflects a continuum rather than strictadherence to one of these four categories, and the classification has not beenshown to predict consistently the success of vaginal delivery For these reasons,this classification is of little clinical use The bony pelvis is assessed bypelvimetry (ie, quantitative measurement of pelvic capacity), which can be

Imaging techniques have defined average and critical limit values for the various

value, however, because they are not able to predict consistently women at risk

clinical use are generally avoided in pregnancy because of the theoretic risks to

replaced, in large part, by clinical trial of the pelvis (a ‘‘trial of labor’’).The soft tissues of the birth canal (ie, cervix, pelvic floor musculature) alsoprovide resistance to the progress of labor and, as such, are important variablesthat allow for successful vaginal delivery For several weeks before delivery, theconnective tissues of the cervix undergo biochemical changes in preparation forlabor, including alterations in water, collagen, elastin, and proteoglycancomposition These changes result in changes to the physical properties ofelasticity, plasticity, and tensile strength Our understanding of the factorsresponsible for cervical effacement and dilation in labor remains unclear Someinvestigators have suggested that the primary factors leading to cervical dilatationare the traction forces of the myometrial contractions, whereas others argue thatthe pressure of the fetal head is the most important determinant The widely heldbelief that amniotomy (artificial rupture of the forebag) increases the pressure offetal head on the cervix has been disputed by recent studies that have measuredpressure objectively between the fetal head and the cervix before and after

an important mediator of uterine quiescence and cervical competence beforelabor, whereas this same agent acting through the cyclic guanosine mono-phosphate signal transduction pathway in labor may promote uterine contractilityand cervical effacement.

In the second stage of labor, the musculature of the pelvic floor is the mainsource of soft-tissue resistance to fetal descent and delivery These muscles arebelieved to play an important role in facilitating rotation and flexion of the fetalhead as it passes through the birth canal For example, internal rotation is known

to occur when the fetal head descends to the level of the pelvic floor, resulting

in 95% of vertex infants delivering in the most favorable (occiput anterior)

pelvic floor musculature with the use of early epidural analgesia may be

Stages and duration of normal labor

Although labor is a continuous process, it traditionally has been divided intothree stages to facilitate study and assist in clinical management

First stage

The first stage refers to the interval between the onset of labor and full cervical

of cervical dilatation (Fig 6):

1 Latent phase The latent phase refers to the period between the onset oflabor and the point at which a change in the slope of the rate of cervical

and is of variable duration

2 Active phase This phase is associated with a faster rate of cervical

The active phase is broken down further into an acceleration phase, a phase

of maximum slope, and a deceleration phase, but these subdivisions arerarely used currently

3 Descent phase Descent of the fetus usually coincides with the second stage

of labor A distinct descent phase was included in the original descriptions[50–52] The existence of a separate descent phase is not universallyaccepted, however

The characteristics of the labor curve do not differ among ethnic or racial

[50–52] determined the average duration for each stage of labor in these twogroups of parturients and calculated the maximum duration of each stage, de-

fined as two standard deviations from the mean (Table 1) For example, theminimum rate of cervical dilatation of 1.2 cm/h for a nulliparous patientrepresents two standard deviations below the mean rate of cervical dilatationfor nulliparas, not the average rate of dilatation among these women (which is

3 cm/h) By comparing a parturient’s rate of cervical dilatation with the normalprofile described by Friedman, it is possible to detect abnormal labor patterns andidentify pregnancies at risk for adverse events This task can be facilitated by use

which a patient’s progress in labor is plotted In this way, abnormal labor patternscan be identified easily and appropriate measures taken

Second stage

The second stage of labor refers to the interval between full cervicaldilatation (10 cm) and delivery of the infant It is characterized by descent ofthe presenting part through the maternal pelvis and culminates with expulsion ofthe fetus Indications that the second stage has started are an increase in bloodyshow, maternal desire to bear down with each contraction, a feeling of pressure

on the rectum accompanied by the desire to defecate, and onset of nausea andvomiting The mother typically assumes a more active role in the second stage

Fig 6 Cervical dilation curve for nulliparous labor (Data from Friedman EA Labor: clinical evaluation and management 2nd edition Norwalk (CT): Appleton-Century-Crofts; 1978.)

than the first stage because she pushes or bears down to aid descent of the fetus.

In the presence of a reassuring fetal heart rate, it is desirable for a nulliparouspatient without regional anesthesia to push for as long as 2 hours (3 hours withregional anesthesia) before resorting to interventions to facilitate delivery

mater-nal or fetal compromise, however, longer times are not associated with creased morbidity

in-Third stage

The third stage of labor refers to the time from delivery of the baby toseparation and expulsion of the placenta and fetal membranes The three classicsigns of placental separation are (1) lengthening of the umbilical cord, (2) a gush

of blood from the vagina, which signifies separation of the placenta from theuterine wall, and (3) a change in the shape of the uterine fundus from discoid toglobular, with elevation of the fundal height The major complication associatedwith this period is hemorrhage, which remains an important cause of maternalmorbidity and mortality Average blood loss at delivery is generally estimated to

be 500 mL Obstetric care providers should be alert to excessive blood lossand should be prepared to intervene as required There are no uniform criteria forthe normal length of the third stage of labor Retention of the placenta for longerthan 30 minutes at term is a commonly used endpoint for intervention even in the

Table 1

Progression of spontaneous labor at term

Stage of labor

Duration of the first stage (hours) 8.0 h 18.8 h Duration of the second stage (minutes) 8.5 min 46.5 min Duration of latent phase (hours) 4.8 h 13.6 h Rate of cervical dilatation during active phase (cm/h) 5.7 cm/h 1.5 cm/h Duration of the third stage (minutes) 5.0 min 30.0 min Data from Norwitz ER, Robinson JN, Repke JT Labor and delivery In: Gabbe SG, Niebyl JR, Simpson JL, editors Obstetrics: normal and problem pregnancies 4th edition New York: Churchill- Livingstone; 2001 p 353–400; with data from Friedman EA Labor: clinical evaluation and management 2nd edition Norwalk (CT): Appleton-Century-Crofts; 1978.

Fig 7 The cardinal movements of labor (From Norwitz ER, Robinson JN, Repke JT Labor and delivery In: Gabbe SG, Niebyl JR, Simpson JL, editors Obstetrics: normal and problem pregnancies 4th edition New York: Churchill-Livingstone; 2001 p 353–400; with permission.)

absence of active hemorrhage The World Health Organization defines a retained

Cardinal movements in labor

The cardinal movements of labor refer to changes in the position of the fetalhead during its passage through the birth canal Because of asymmetry in theshape of the fetal head and the maternal bony pelvis, such rotations are required

if the fetus is to negotiate the birth canal successfully These seven discretemovements are engagement, descent, flexion, internal rotation, extension,external rotation or restitution, and expulsion (Fig 7)

the fetal presenting part to a level below the plane of the pelvic inlet Inthe cephalic presentation with a well-flexed head, the largest transversediameter of the fetal head is the biparietal diameter (9.5 cm) In the breech,the widest diameter is the bitrochanteric diameter Engagement can beconfirmed clinically by palpation of the presenting part abdominally (whenonly two fifths of the head can be palpated abdominally) or vaginally (withconfirmation of station at or below the ischial spines) Engagement is animportant clinical milestone in the progress of labor, because it demonstratesthat the bony pelvis is adequate to allow passage of the fetal head Formultiparous women, engagement may occur at any time after 36 weeks Inprimipara, however, failure of engagement to take place by 36 weeks is

through the pelvis Descent of the fetus is not a steady, continuous process.The greatest rate of descent occurs during the deceleration phase of the firststage and during the second stage of labor

because of the shape of the bony pelvis and the resistance of the soft tissues

of the pelvic floor Although flexion of the fetal head onto the chest ispresent to some degree in most fetuses antepartum, complete flexion usuallyonly occurs during the course of labor With the head completely flexed, thefetus presents the smallest diameter of its head (suboccipito-bregmaticdiameter), which allows optimal passage through the pelvis

 Internal rotation Internal rotation is the rotation of the presenting part fromits original position (usually transverse with regard to the birth canal) to theanteroposterior position as it passes through the pelvis This changetypically results in the fetal occiput rotating toward the symphysis pubis

as it descends, which leads to the widest axis of the fetal head lining up withthe widest axis of the pelvic passage The curvature of the maternal sacrumcauses the fetal head to descend in an asynclitic fashion at first, but ittypically corrects As with flexion, internal rotation is a passive movement

that results from the shape of the pelvis and the resistance of the pelvicfloor musculature

the introitus This descent brings the base of the occiput into contact with theinferior margin of the symphysis pubis At this point, the birth canal curvesupward The fetal head is delivered by extension and rotates around thesymphysis pubis The forces responsible for this motion are the downwardforce exerted on the fetus by uterine contractions and maternal expul-sive efforts along with the upward forces exerted by the muscles of thepelvic floor

rotates to the correct anatomic position in relation to the fetal torso; left orright rotation depends on the orientation of the fetus This is again a passivemovement that results from a release of the forces exerted on the fetal head

by the maternal bony pelvis and its musculature, and it is mediated by thebasal tone of the fetal musculature

delivery of the head and external rotation, further descent brings the anteriorshoulder to the level of the symphysis pubis The anterior shoulder rotatesunder the symphysis pubis, after which the rest of the body usually deliverswithout difficulty

Maternal pushing in labor

The cardinal movements are largely the result of uterine contractions and thepassive action of the pelvic musculature and soft tissues of the descending fetalhead Obstetric practice in the United States often dictates that the parturientbegin to bear down (push) in concert with each contraction when the cervixattains full dilation (10 cm), even if she does not feel the urgency to do so.Despite the widespread implementation of this practice, it is not clear whether

quadriplegia who are unable to push voluntarily are able to deliver vaginallywithout difficulty Recent studies suggest that most of the increased intrauterinepressure in the second stage of labor results from uterine contractions, with only asmall contribution from maternal expulsive efforts even under optimal conditions

The timing of maternal pushing is also debated Several recent randomizedprospective studies have questioned the practice of encouraging pushing at thebeginning of the second stage and have suggested that pushing be delayed for

a large (n = 1862), randomized, multicenter study documented that delayedpushing for 1 hour was an effective means of reducing ‘‘difficult deliveries’’ in

nulliparous women (relative risk (RR), 0.79; 95% confidence interval (CI),

deliver-ies (RR, 0.72; 95% CI, 0.55–0.93) Delayed pushing predictably increasedthe duration of the second stage (by 54 minutes) and resulted in lower umbilicalcord blood pH, but no difference was detected in overall neonatal morbidity

Summary

Labor is a physiologic and continuous process The factors responsible forthe onset and maintenance of normal labor at term are poorly understood andcontinue to be under active investigation Although data exist to describe theaverage duration of labor, there is also a great deal of biologic variability Animproved understanding of the causes and mechanisms of labor will improvethe ability of clinicians to distinguish normal from abnormal labor and to inter-vene in a timely and effective fashion to ensure a favorable outcome whilemoving toward a more individualized approach to each woman’s labor

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[37] O’Brien WF, Cefalo RC Evaluation of X-ray pelvimetry and abnormal labor Clin Obstet Gynecol 1982;25(1):157 – 64.

[38] Joyce DN, Giwa-Osagie F, Stevenson GW Role of pelvimetry in active management of labour BMJ 1975;4(5995):505 – 7.

[39] van Loon AJ, Mantingh A, Serlier EK, et al Randomised controlled trial of magnetic-resonance pelvimetry in breech presentation at term Lancet 1997;350(9094):1799 – 804.

[40] Pattinson RC Pelvimetry for fetal cephalic presentations at term Cochrane Database Syst Rev 2000;2:CD000161.

[41] Morris CW, Heggie JC, Acton CM Computed tomography pelvimetry: accuracy and radiation dose compared with conventional pelvimetry Australas Radiol 1993;37(2):186 – 91.

[42] Manabe Y, Sagawa N Changes in the mechanical forces of cervical distention before and after rupture of the membranes Am J Obstet Gynecol 1983;147(6):667 – 71.

[43] Vaisanen-Tommiska M, Nuutila M, Ylikorkala O Cervical nitric oxide release in women postterm Obstet Gynecol 2004;103(4):657 – 62.

[44] Okawa T, Vedernikov YP, Saade GR, et al Effect of nitric oxide on contractions of uterine and cervical tissues from pregnant rats Gynecol Endocrinol 2004;18(4):186 – 93.

[45] Chen DC, Ku CH, Huang YC, et al Urinary nitric oxide metabolite changes in spontaneous and induced onset active labor Acta Obstet Gynecol Scand 2004;83(7):641 – 6.

[46] Buhimschi IA, Yallampalli C, Buhimschi CS, et al Distinct regulation of nitric oxide and cyclic guanosine monophosphate production by steroid hormones in the rat uterus Mol Hum Reprod 2000;6(5):404 – 14.

[47] Buhimschi I, Yallampalli C, Dong YL, et al Involvement of a nitric oxide-cyclic guanosine monophosphate pathway in control of human uterine contractility during pregnancy Am J Obstet Gynecol 1995;172(5):1577 – 84.

[48] Cunningham F, Gant NF, Leveno KJ, et al Williams obstetrics 21st edition New York7 McGraw-Hill; 2001.

[49] Ponkey SE, Cohen AP, Heffner LJ, et al Persistent fetal occiput posterior position: obstetric outcomes Obstet Gynecol 2003;101(5 Pt 1):915 – 20.

[50] Friedman E The graphic analysis of labor Am J Obstet Gynecol 1954;68(6):1568 – 75 [51] Friedman EA Primigravid labor: a graphicostatistical analysis Obstet Gynecol 1955;6(6):

[57] The prevention and management of postpartum haemorrhage: report of a technical working group Geneva7 World Health Organization/Maternal and Child Health and Family Planning; 1990 [58] Mayberry LJ, Hammer R, Kelly C, et al Use of delayed pushing with epidural anesthesia: findings from a randomized, controlled trial J Perinatol 1999;19(1):26 – 30.

[59] Thomson AM Pushing techniques in the second stage of labour J Adv Nurs 1993;18(2):

prog-[62] Vause S, Congdon HM, Thornton JG Immediate and delayed pushing in the second stage

of labour for nulliparous women with epidural analgesia: a randomised controlled trial Br J Obstet Gynaecol 1998;105(2):186 – 8.

[63] Fraser WD, Marcoux S, Krauss I, et al Multicenter, randomized, controlled trial of delayed pushing for nulliparous women in the second stage of labor with continuous epidural analgesia: the PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group Am J Obstet Gynecol 2000;182(5):1165 – 72.

[64] Petrou S, Coyle D, Fraser WD Cost-effectiveness of a delayed pushing policy for patients with epidural anesthesia: the PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group Am J Obstet Gynecol 2000;182(5):1158 – 64.

Labor with Abnormal Presentation and Position Michael L Stitely, MDa,*, Robert B Gherman, MDb

a

Department of Obstetrics and Gynecology, West Virginia University School of Medicine,

1 Medical Center Drive, PO Box 9186, Morgantown, WV 26506-9186, USA

b

Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine,

Washington Adventist Hospital, Takoma Park, MD, USA

The fetus delivers in the cephalic presentation in approximately 97% ofdeliveries Abnormal presentation—usually the breech presentation—complicatesthe remaining 3% of deliveries

Breech presentation

There is considerable controversy concerning the optimal route of delivery for

a fetus that presents in the breech position A full discussion of this issue

is beyond the scope of this article Diagnosis and management options arediscussed, however

Etiology

The prevalence of breech presentation depends on gestational age Scheer

ges-tational ages They found that at 21 to 24 weeks’ gestation, 33.3% of fetuses were

in the breech position By contrast, only 6.7% of fetuses were in the breechposition at 37 to 40 weeks’ gestation Other risk factors for breech presentationinclude multiparity, previous breech delivery, polyhydramnios, fetal anomalies,and uterine anomalies

0889-8545/05/$ – see front matter D 2005 Elsevier Inc All rights reserved.

* Corresponding author.

E-mail address: mstitely@hsc.wvu.edu (M.L Stitely).

32 (2005) 165 – 179

The diagnosis of breech presentation can be made reliably using a bination of abdominal palpation and vaginal examination The first Leopoldmaneuver detects the fetal head at the fundal aspect of the uterus Vaginalexamination and palpation reveal either the ischial tuberosities and sacrum or—infootling breech presentations—the lower extremities When the cervix is dilatedand the membranes are ruptured, the fetal anus may be identified on examination.Ultrasound can be used to confirm the presentation, classify the type ofbreech presentation, assess the estimated fetal weight, and identify gross fetalanomalies Complete breech presentations have both hips flexed with one or bothknees flexed Incomplete breech presentations have one or both hips extended.Frank breech presentations have both hips flexed and both knees extended.Management

com-Patients should be offered external cephalic version when breech presentation

is diagnosed in late pregnancy The Cochrane Database of Systematic Reviewsaddressed the issue of external cephalic version of breech presentation at term[2].Six randomized trials were included in the review External cephalic version

at term significantly reduced the incidence of noncephalic births (Relative risk0.42, 95% confidence interval 0.35–0.5) and cesarean delivery (Relative risk0.52, 95% confidence interval 0.39–0.71) without a significant effect on peri-natal mortality

Technique

External cephalic version can be performed with either one or two operators.The procedure should be performed in a setting in which the fetus can bemonitored and an immediate cesarean delivery can be performed if necessary.Contraindications include third-trimester bleeding, oligohydramnios, rupturedmembranes, severe fetal anomalies, and the usual contraindications to vaginalbirth (ie, placenta previa, prior classical cesarean delivery, vasa previa).Results of a reactive non–stress test should be obtained before the procedure,and the patient should undergo counseling for informed consent before theprocedure Ultrasound should be performed to confirm the breech presentationand assess the amniotic fluid volume Administration of beta-mimetic tocolytics

The patient should be tilted laterally to prevent supine hypotension Firstthe fetal breech is elevated out of the maternal pelvis The version is then per-formed by attempting to turn the fetus into a forward roll If attempts at inducing

a forward roll motion are unsuccessful, the opposite direction may be attempted.The amount of force exerted is gauged by the patient’s pain tolerance The use

of spinal or epidural analgesia is controversial Some trials have shown benefit[4,5], whereas others have not[6] After the version attempt, the fetus should be

monitored for a minimum of 30 minutes Rh immunoglobulin should beadministered to Rh-negative patients A suggested algorithm for external cephalic

Route of delivery for the persistent breech presentation

For patients who undergo a failed version attempt or patients who decline an

still exists over this recommendation

that assessed the safety of a trial of planned vaginal delivery versus plannedcesarean delivery for fetuses with breech presentation They found a decrease

in perinatal and neonatal mortality and a decrease in serious perinatal morbidity

in the planned cesarean delivery group (Relative risk 0.33, 95% confidenceinterval 0.19–0.56) Criticism of the study by Hannah et al includes the inclusioncriteria of the study In this trial, pelvimetry was assessed by clinical examination

excluded 46% of the patients assigned to the planned vaginal delivery group

Patient desires external cephalic version and informed consent obtained

Reassuring test of fetal wellbeing (nonstress test or biophysical profile) and adequate amniotic fluid volume

Perform external cephalic version

Consider administration of betamimetic tocolytic

Version unsuccessful Version successful

Converts back to breech Spontaneous conversion tocephalic presentation

Consider repeat attempt at external cephalic version or plan delivery by Cesarean

Continue routine prenatal care and attempt vaginal delivery

Consider repeat attempt at external cephalic version or plan delivery by Cesarean Remains breech

Breech presentation beyond contraindications for vaginal birth

Remains cephalic

Continue routine prenatal

care and attempt vaginal

delivery

Fig 1 Algorithm for the management of breech presentation diagnosed at or beyond 36 weeks’ gestation.

Other criticisms of the trial by Hannah et al include the facts that the estimatedfetal weight was assessed by clinical examination only in more than 40% ofthe patients, the attitude of the fetal head was assessed by clinical examinationonly in more than 30% of patients, and continuous electronic fetal monitoringwas not performed in all patients Some clinicians would argue that it is notsurprising that this trial found a decrease in perinatal and neonatal mortality andserious perinatal morbidity in the planned cesarean delivery group because it wasessentially a trial of planned vaginal birth in unselected patients versus plannedcesarean delivery The American College of Obstetricians and Gynecologistshas recommended cesarean delivery for all women with a persistent breech

Simulation training in the techniques of assisted vaginal breech deliveryshould be considered by all residency training programs to ensure that allclinicians are adequately prepared for the inevitable situation of a patientpresenting with the breech on the perineum without enough time to undergocesarean delivery safely[11]

Transverse lie

Etiology

Risk factors include placenta previa, multiparity, polyhydramnios, contractedpelvis, fetal prematurity, and uterine anomalies

Diagnosis

Abdominal palpation and inspection usually suggest transverse lie The fetalhead can be palpated on one side of the maternal abdomen and the breech inthe other Ultrasound should be used to assess placental location

Management

with transverse lie converted to a longitudinal lie with expectant management.Expectant management of the transverse lie yielded major neonatal and ma-ternal morbidity, however, with two cases of cord prolapse, one case of uterinerupture, and one neonatal death in the study group of 29 patients A policy ofexternal cephalic version beyond 37 weeks’ gestation—with cesarean deliveryfor patients with failed version or persistent transverse lie—is prudent

When cesarean delivery is performed for a fetus in transverse lie, a classicaluterine incision should be considered to allow for atraumatic delivery of theneonate An intra-abdominal version may be performed to convert the fetus to a

longitudinal lie (either cephalic or breech) to allow for a low transverse uterine

Face presentation

Etiology

Face presentation is caused by hyperextension of the fetal head Factorsassociated with face presentation include a contracted pelvic inlet, anencephalicfetus, fetal macrosomia, or high parity

Diagnosis

The diagnosis of face presentation is usually obvious on vaginal tion during labor Classification using the position of the mentum should beperformed If an ultrasound anatomic review has not been performed earlier inthe pregnancy, anencephaly should be excluded by ultrasound

examina-Management

The management of face presentation is expectant Vaginal manipulationand rotational maneuvers are associated with an increased risk of perinatal

progresses normally in labor and delivers vaginally Mentum transverse positionsfrequently rotate spontaneously to mentum anterior positions and deliver vagi-nally Persistent mentum posterior positions cannot deliver vaginally and aredelivered by cesarean section If labor progresses normally in the mentumposterior position, however, the patient can be managed expectantly Thisprogression is allowed because of the finding that spontaneous rotation from thementum posterior position to the mentum anterior position may not occur untilthe presenting part is on the pelvic floor Oxytocin augmentation of labor is notcontraindicated in a face presentation

Forceps delivery should be restricted to outlet procedures Instrumental tions and midforceps procedures for face presentations have a high risk of fetal

presentation is as follows Forceps should be applied only to the mentum anteriorposition Instrumental delivery should be attempted only when the presentingfetal face is on the pelvic floor In any other situation, the actual station ismisleading because the biparietal diameter actually may be at or above the level

of the ischial spines, which makes any attempt at instrumental delivery, bydefinition, a high forceps procedure

Kielland forceps or a classical instrument may be used for instrumentaldelivery of the face presentation Forceps application is performed by using thefetal chin to replace the occiput as a landmark and using the fetal mouth to

replace the posterior fontanelle as a landmark Downward traction is applied tomaintain extension until the chin passes under the symphysis pubis The handles

of the forceps are then elevated to effect delivery of the occiput over the perineum.Forceps procedures for the mentum posterior and mentum transverse positionsare dangerous and should not be attempted Vacuum delivery of the facepresentation is contraindicated for obvious reasons

Brow presentation

Etiology

Brow presentation occurs because of partial deflexion of the fetal head

Diagnosis

The diagnosis of brow presentation is made by vaginal examination Theposterior fontanelle, mouth, and chin cannot be palpated in the brow presentation.Ultrasound to exclude major anomalies or macrosomia should be considered.The position is defined using the anterior fontanelle as the reference point(ie, frontum anterior or frontum posterior)

Management

More than 50% of brow presentations convert by flexion to vertex

brow presentation is expectant Vaginal delivery occurs in less than one third of

or arrests, cesarean delivery is performed Attempts to deliver instrumentally ormanipulate the fetus vaginally to vertex or face presentation are dangerous andare contraindicated

Compound presentation

A compound presentation involves the prolapse of an extremity alongsidethe presenting head or breech This situation is encountered more frequentlywith preterm deliveries than full-term deliveries because of incomplete occlusion

of the pelvis by the fetal head Management is expectant, and often the prolapsedarm retracts and allows descent of the presenting part If the arm does not retract,

it can be pushed gently upward, after which fundal pressure is applied todescend the fetal head Umbilical cord prolapse can occur in the presence of acompound presentation

Occiput transverse position

Etiology

The occiput transverse position is frequently encountered in labor as atransitory position With time and adequate uterine inertia, rotation to occi-put anterior (or sometimes occiput posterior) position usually occurs Someconditions predispose to a persistent occiput transverse position, such as aplatypelloid or android pelvic type

Diagnosis

The diagnosis of occiput transverse position is made by vaginal examination.Classification is made by the position of the occiput If significant molding hasoccurred, palpation of the helix of the fetal ear can confirm the position.Management

Most occiput transverse positions rotate spontaneously to occiput anterior

or occiput posterior positions Some clinical situations, such as fetal heartabnormalities in the second stage of labor or persistent occiput transverse posi-tions, require operative intervention

Digital rotation should be attempted when persistent occiput transversepositions or fetal heart rate abnormalities are encountered in the second stage

of labor Anesthesia usually is not necessary to perform digital rotation For theleft occiput transverse position, the index and middle fingers of the operator’sright hand are placed along the lambdoidal suture The thumb is then placedalong the parietal bone Counterclockwise rotation is used Once the head rotates

to the occiput anterior (or left occiput anterior) position, the index and middlefingers are used to hold the fetal head in place while maternal expulsive effortsare used to descend the fetal head or forceps are applied The technique is similarfor the right occiput transverse position, except that the operator uses the left handand rotation is performed in the clockwise direction

If digital rotation is unsuccessful, manual rotation can be attempted Pudendal

or epidural analgesia is usually necessary for this procedure For the left occiputtransverse position, the operator’s right hand is used The four fingers of theright hand are inserted into the posterior aspect of the vagina and the thumb isplaced on the fetal right parietal bone Counterclockwise rotation is then per-formed Care should be taken not to disengage the fetal head because it can lead

to umbilical cord prolapse After successful rotation, the four fingers are left inplace to hold the fetal head in the occiput anterior position while either maternalexpulsive efforts are used to descend the head or forceps are applied The rightocciput transverse position is manually rotated in similar fashion, except theoperator’s left hand is used and the rotation is clockwise

The vacuum extractor can be applied to occiput transverse positions Caremust be taken to avoid applying torque to the device ‘‘Autorotation’’ can occurfrom the resistance placed on the fetal head by the pelvic floor musculature tocause rotation to occiput anterior as descent occurs.

Instrumental rotation of the occiput transverse position can be accomplishedwith either classical forceps, such as Elliot or Simpson forceps, or with theKielland forceps

Rotation with classical forceps

In the left occiput transverse position, the posterior (left) blade is inserted first.The blade is applied directly and is guided with the index and middle fingers

of the operator’s right hand The anterior (right) blade is then introduced using

a pelvic application on the maternal right side The blade is then ‘‘wandered’’across the fetal face by creating an arc with the handle while gently elevating theforcep blade with the index and middle fingers The handle of the anterior blade isthen elevated to lock the handles The shanks should be angled toward the occiput.Rotation with classical forceps uses a wide arcing motion, similar to turning ahandle on a wrench (unlike the twisting motion used with the Kielland forceps,which is not unlike turning the handle of a screwdriver) The fetal head should

be flexed before initiating rotation When the proper arc is used, the toes ofthe blades remain in one plane and the handles arc in a circular fashion 908 inthe counterclockwise direction Using the proper plane of rotation minimizesmaternal soft-tissue injury If resistance is met, the fetus can be elevated slightly

to ‘‘de-station’’ the fetus Care must be taken not to cause disengagement,however, which can lead to umbilical cord prolapse

Once successful rotation is achieved, the positioning of the forceps should bereassessed Once proper alignment is assured, traction using the Pajot-Saxtorphmaneuver is used to effect delivery

Application of classical forceps to the right occiput transverse position isaccomplished in similar fashion The posterior (right) blade is applied directly.The anterior (left) blade is inserted with pelvic application to the maternal leftside It is then ‘‘wandered’’ anteriorly One difference between application to theleft and right occiput transverse positions is that the forceps blades must becrossed to lock the handles in the right occiput transverse position Rotation ofthe right occiput transverse position is accomplished with 908 rotation in theclockwise direction using the same arcing technique used for the left occiputtransverse position

Rotation with Kielland forceps

Instrumental rotation with Kielland forceps gives the added advantage ofbeing able to correct anterior asynclitism with the sliding lock on the handles

There are three application methods for applying Kielland forceps to put transverse positions Each technique is described for the left occiput trans-verse position.

occi-Wandering technique

The application of the Kielland forceps should be preceded by a ‘‘shadow’’application, in which the forceps are positioned and the direction of rotation ispracticed while facing the patient before the actual application is performed.Unlike most forceps applications, Kielland forceps application to the occiputtransverse position requires placement of the anterior blade first In the leftocciput transverse position, the anterior (right) blade is placed with a pelvicapplication to the maternal right side The index and middle finger of theoperator’s left hand then guide the blade in clockwise direction around the facewhile the handle is depressed using counterpressure

Classical (inversion) technique

As with all forceps applications, the bladder should be emptied before forcepsapplication For the left occiput transverse position, the anterior (right) blade isheld in the inverted position, with the handle elevated approximately 458 Theanterior blade is then slid under the pubic bone in the inverted position Ifresistance is met, this application method should be abandoned and thewandering method used As the blade enters the uterus beyond the pubicsymphysis, the handle should be lowered At this point the toe of the blade can befelt or seen through the abdominal wall above the symphysis pubis The handle isthen grasped and flipped 1808 to position the cephalic curve properly to the side

of the fetal head Potential complications of the classical application techniqueinclude bladder laceration and uterine perforation

Direct application technique

The direct application technique may be used with the transverse position deep

in the pelvis with anterior asynclitism This particular situation makes applicationwith the classical or wandering methods difficult For the left occiput transverseposition, the anterior (right) blade is applied directly to the parietal bone, and theblade advances from below until it is properly positioned on the cheek.The posterior blade is then applied directly within the posterior vagina and thehandles are locked Once the application of the forceps is checked, asynclitism iscorrected using the sliding lock design of the Kielland forceps by aligning theknobs located on the anterior surface of the finger guards Rotation isaccomplished by first flexing the fetal head A direct turning motion with thewrist effects rotation in the counterclockwise direction If resistance isencountered, the fetus can be ‘‘de-stationed’’ to facilitate the rotation

Persistent occiput transverse position or fetal indications for delivery in occiput transverse position

Digital rotation successful

Spontaneous or operative vaginal delivery

Successful

Instrumental rotation with Classical or Kielland forceps or vacuum

No

No Yes

Manual rotation successful Spontaneous or operative

Once rotation is completed, the forceps placement is reassessed for properalignment Once the proper alignment is assured, delivery is effected withdownward traction Because of the reverse pelvic curve of the instrument,the angle of traction is somewhat lower than that of the classical forceps Someobstetricians prefer changing forceps to a classical instrument after the success-ful rotation This maneuver can allow the fetus to revert back to the transverseposition if the reapplication is not performed swiftly, however A summary ofthe management of the occiput transverse position can be seen in the algorithm

posterior positions at the time of delivery occur because of malrotation during

epidural analgesia did not contribute to occiput posterior positions at the time

of delivery

Diagnosis

Occiput posterior position can be suspected by noting an indentation on thematernal abdomen by inspection or palpation The diagnosis is made on vaginalexamination by palpating the lambdoidal suture in the posterior position.Palpation of the helix of the fetal ear confirms the diagnosis

Management

The presence of an occiput posterior position in labor is not an absolute

552 cases of occiput posterior deliveries and found that 33.8% of women ered spontaneously and that 95.6% of women delivered vaginally More recently,

posi-tions and found that 40% delivered spontaneously and 78% delivered vaginally.The significant risks associated with the delivery of a fetus in the occiputposterior position include approximately a sevenfold increase in anal sphincter

position Provided that labor progress is normal and fetal status is reassuring,expectant management and spontaneous delivery in the occiput posterior positionare indicated If the second stage of labor arrests or is protracted or if the fetalstatus warrants intervention, then operative delivery is indicated.

If the pelvic outlet is adequate and there is adequate space in the posteriorpelvis and vagina, vacuum or forceps delivery in the occiput posterior position isperformed Elliot or Simpson forceps (with or without an axis-traction handle) orforceps with an axis-traction design (eg, Hawks-Dennen) are used The forceps areplaced so that the posterior fontanelle is just inferior to the shanks and the sagittalsuture is in the midline and perpendicular to the plane of the shanks Traction is inthe horizontal direction until the bridge of the nose is at the pubic symphysis Thehandles are then gradually elevated to effect delivery of the face and chin If there

is not sufficient room in the pelvic outlet and posterior vagina to allow for delivery

in the occiput posterior position, a rotational maneuver can be attempted

Manual rotation

Manual rotation is performed by inserting a hand into the vagina with thepalm directed upward The fingers and thumb are placed on opposite sides of thefetal head The direction of rotation is guided toward the side of the fetal back Anabdominal hand can be used to assist in rotating the fetal shoulders The fetalhead can be ‘‘de-stationed’’ to assist in rotation, but care should be taken not tocause disengagement Once successful rotation to the occiput anterior position

is accomplished, delivery can be accomplished by placing forceps for delivery

or by beginning maternal expulsive efforts for spontaneous delivery

Scanzoni maneuver

Classical instruments, such as the Elliot or Simpson forceps, can be used forthe rotation of the occiput posterior position to occiput anterior position Theforceps are placed using a pelvic application as if applying the forceps to anocciput anterior position After confirming the proper placement of the forceps,the fetal head is flexed Rotation then begins in the direction of the fetal back Thehandles of the forceps are arced to keep the toes of the blades in the plane

of the pelvis

After rotation, the forceps are in the upside-down configuration and must beremoved and reapplied Having a second set of forceps available allows forreplacement of the forceps without having to remove both blades, which preventsreversion to an occiput transverse or occiput posterior position Otherwise,both blades are removed and reinserted with the pelvic curve properly positioned.Delivery is then accomplished in the usual fashion for an occiput anterior position

Kielland forceps rotation

The Kielland forceps are applied upside-down to the occiput posteriorposition This position allows for rotation, traction, and delivery without having

to remove the forceps

A shadow application should be performed first Then, with the knobs onthe finger guards facing the floor, the forceps are applied The fetal head is flexedand rotation is performed by twisting the wrist (much like applying torque to a

Unsuccessful

Forceps rotation (Scanzoni or Kielland) Operative vaginal delivery

with forceps or vacuum in the occiput anterior position

Persistent occiput posterior position in second stage labor

Progressing normally in labor

Successful

Operative vaginal delivery with forceps or vacuum in the occiput posterior position

Attempt at manual rotation

Deliver spontaneously in the

occiput posterior position

Fig 3 Algorithm for the management of the persistent occiput posterior position.

screwdriver) in the direction of the fetal back An abdominal hand can be used toassist in rotating the fetal shoulders The fetal head can be de-stationed ifresistance is met Once rotation is completed to the occiput anterior position,traction can be applied and delivery performed with the Kielland forceps, orthe Kielland forceps can be removed and replaced (one blade at a time) with aclassical instrument that is better suited for traction and delivery A suggestedmanagement algorithm for the management of persistent occiput posteriorposition is described inFig 3.

Whenever an obstetrician encounters resistance to rotation that cannot beovercome by flexing or de-stationing the fetal head or if descent does not occureasily after rotation, cesarean delivery should be performed

Summary

Abnormal presentation and position are infrequently encountered duringlabor Breech and transverse presentations should be converted to cephalic pre-sentations by external cephalic version or delivered by cesarean section Face,brow, and compound presentations are usually managed expectantly Persistentocciput transverse positions are managed by rotation to anterior positions anddelivered as such Occiput posterior positions can be delivered as such or rotated

to occiput anterior positions As with any position or presentation, the cian should not hesitate to abandon any rotational or operative vaginal procedureand proceed to cesarean delivery if rotation or descent does not occur withrelative ease

of external cephalic version: a randomized trial Obstet Gynecol 1999;93(3):345 – 9.

[7] Hofmeyr GJ, Hannah ME Planned cesarean section for term breech delivery Cochrane Database Syst Rev 2003;3:CD000166.

[8] Hannah ME, Hannah WJ, Hewson SA, et al Planned caesarean section versus planned vaginal birth for breech presentation at term: a randomised multicentre trial Lancet 2000;356(9239):

1375 – 83.

[9] Collea JV, Chein C, Quilligan EJ The randomized management of term frank breech presentation: a study of 208 cases Am J Obstet Gynecol 1980;137(2):235 – 44.

[10] American College of Obstetricians and Gynecologists Mode of term singleton breech delivery: committee opinion number 265 Washington, DC7 American College of Obstetricians and Gynecologists; 2001.

[11] Macedonia CR, Gherman RB, Satin AJ Simulation laboratories for training in obstetrics and gynecology Obstet Gynecol 2003;102(2):388 – 92.

[12] Cruikshank DP, White CA Obstetric malpresentations: twenty years’ experience Am J Obstet Gynecol 1973;116(8):1097 – 104.

[13] Phelan JP, Boucher M, Mueller E, et al The nonlaboring transverse lie A management dilemma.

[18] Gardberg M, Laakkonen E, Salevaara M Intrapartum sonography and persistent occiput posterior position: a study of 408 deliveries Obstet Gynecol 1998;91(5 Pt 1):746 – 9 [19] Yancey MK, Zhang J, Schweitzer DL, et al Epidural analgesia and fetal head malposition

at vaginal delivery Obstet Gynecol 2001;96(4):608 – 12.

[20] Phillips RD, Freeman M The management of the persistent occiput posterior position:

a review of 552 consecutive cases Obstet Gynecol 1974;43(2):171 – 7.

[21] Fitzpatrick M, McQuillan K, O’Herlihy C Influence of persistent occiput posterior position

on delivery outcome Obstet Gynecol 2001;98(6):1027 – 31.

Induction of Labor Luis Sanchez-Ramos, MDDepartment of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, University of Florida Health Science Center, 653-1 West 8thStreet, Jacksonville, FL 32209, USA

Induction of labor is one of the most common procedures in obstetricsand one of the fastest growing medical procedures in the United States The rate

of labor induction in the United States continues to rise significantly for allgestational ages Final data for the year 2003 from the National Center forHealth Statistics indicated that the rate was 20.6% for the year 2002, more than

it may partly reflect a growing use of labor induction for postterm pregnanciesand an increasing trend toward elective induction of labor

Indications and contraindications

Generally, labor induction is indicated when the benefits of delivery to themother or fetus outweigh the potential risks of continuing the pregnancy Themost appropriate timing for labor induction is the point at which the maternal

or perinatal benefits are greater if the pregnancy is interrupted than if thepregnancy is continued Ideally, most pregnancies should be allowed to reachterm, with the onset of spontaneous labor being the sign of physiologictermination of pregnancy Occasionally, however, a woman must deliver beforethe spontaneous onset of labor Commonly accepted indications for labor in-

pregnancy-induced hypertension and postterm pregnancies are among themost common, accounting for more than 80% of reported inductions Unlessthere is evidence of fetal compromise, it is often imperative that pregnancy be atterm or fetal maturity documented Whenever there is evidence of fetal lung

0889-8545/05/$ – see front matter D 2005 Elsevier Inc All rights reserved.

E-mail address: luis.sanchez@jax.uf l.edu

32 (2005) 181 – 200

maturity, the decision to induce labor is not difficult The decision to inducelabor before term is far more difficult, however In such cases, there should beclear benefits to the fetus of premature delivery that far outweigh the potentialproblems associated with preterm birth Although elective induction of labor(without medical or obstetric indications) is generally not recommended, logisticfactors such as distance from the hospital or a history of rapid labor and deliverymay be reasonable indications for elective induction.

Generally recognized relative and absolute contraindications to labor

in-duction, because there may be certain clinical situations in which exceptions

Box 1 Common indications for labor induction

Box 2 Contraindications to labor induction

Absolute