HIGH-RISK PREGNANCY pps

200 HANDBOOK OF OBSTETRICS AND GYNECOLOGYT ABLE 7-1IDENTIFICA TION OF SPECIFIC OBSTETRIC RISK F ACTORS I NITIAL E V ALUATION Biologic F actors High Risk Some Risk Maternal age 15 or 35 M

7 HIGH-RISK PREGNANCY

the morbidity and mortality Some factors contributing to risk are

quite obvious, but others are very subtle Thus, care must be taken

in definitions, screening programs, and application of the toolsavailable for diagnosis and treatment The following is but one ofthe ways to approach this multifaceted set of circumstances

DEFINITION, INCIDENCE,

AND IMPORTANCE

A high-risk pregnancy is one in which the mother or perinate is or will be in jeopardy (death or complications) during gestation or in the puerperium/neonatal interval Estimates of the incidence of

high-risk pregnancy vary widely depending mainly on the criteriaused for definition and the accuracy of the data collection Never-theless, by most standards, ~20% of established pregnancies in the

United States are at some risk and ~5% are at high risk About half

can be identified antenatally and another quarter during labor

(Table 7-1) For example, the majority of perinatal deaths are

as-sociated with prematurity or congenital anomalies If these two

con-ditions are excluded, 60% of fetal and
50% of neonatal deaths are

associated with only five obstetric complications: breech

presenta-tion, premature separation of the placenta, preeclampsia-eclampsia, multiple pregnancy, and urinary tract infection Certain less com-

mon complications (e.g., cord prolapse) also cause an inordinatelyhigh proportion or perinatal losses Of course, a low-risk pregnancy(not endangered by present or foreseeable complications) can be-come high risk at any time

The early identification of risk factors is vital for both

avoid-ance of serious problems and proper treatment of complications

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200 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

T ABLE 7-1IDENTIFICA TION OF SPECIFIC OBSTETRIC

RISK F ACTORS

I NITIAL E V ALUATION

Biologic F actors

High Risk Some Risk

Maternal age 15 or 35 Maternal age 15–19

Morbid obesity
20% of standard height

Poor nutrition for weight

Maternal malignancy 20% of standard height

Ovarian neoplasms for weight

Genetic or familial Short stature (60 inches)

disorder Uterine leiomyomataIncompetent cervix Pelvic or spinal deformityCervical malformation

Birth weight
4000 g Genital tract infectionsGenetic disorder Human papillomavirusCongenital anomaly (HPV)

Isoimmunization Herpes

Eclampsia Gonorrheal

Birth damaged infant Chamydia

Special neonatal care Group B Streptococcus

Medically indicated

pregnancy termination

Molar gestation

HIGH-RISK PREGNANCY 201

Hypertension (moderate to Mild hypertension

severe) Class I heart disease

Severe renal disease Gestational diabetes

Class II–IV heart disease Recurrent urinary

Insulin-regulated diabetes infections

Endocrine ablation (thyroid) Positive serology

Abnormal cervical cytology Sickle cell trait

Sickle cell disease Epilepsy

Pulmonary disease Emotional disorders

Liver disease Smoking

Recurrent pyelonephritis Pelvic inflammatory

Collagen vascular disease disease

Malignancy Previous ectopic Gastrointestinal disease pregnancy

Substance abuse Physical abuse

Heavy smoking (
10 day)

E V ALUATION O N E ACH P RENATAL V ISIT , E ARLY P REGNANCY

(
20 WEEKS )

High Risk Some Risk

Teratic exposure Antenatal diagnosis

Failure of uterine growth indicated

Isoimmunization Unresponsive urinary

Severe anemia tract infection

(9 g Hgb) Possible ectopic gestation

Multiple gestation Missed abortion

Fetal anomalies Severe hyperemesis

Cervical incompetence gravidarum

Insulin-regulated Positive serology

diabetes Sexually transmitted

Fetal anomalies disease

Nonimmune hydrops Unresponsive anemia

Renal agenesis Vaginal bleeding

(Potter’s) Diet-regulated diabetes

T ABLE 7-1

(Continued)

Medical and Sur gical History

High Risk Some Risk

(Continued)

202 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

E V ALUATION ON E ACH P RENATAL V ISIT , L ATER

Isoimmunization Placenta previa

Oligohydramnios Premature onset of laborHydramnios (36 weeks)

Thromboembolic disease Premature rupture (38

Abruptio placentae weeks)

Abnormal antepartum test Chronic or acute

(NST, CST, BPP) pyelonephritis

Prolonged membrane rupture Abnormal fetal positionFetal infections

I NTRAPARTUM E V ALUATION

High Risk Some Risk

High-risk factors above Mild PIH

Severe PIH or eclampsia Rupture of membranes Hydraminos or
12 h

oligohydramnios Primary dysfunctional Amnionitis labor

Prolonged membrane Secondary arrest of rupture (
24 h) dilatation

Uterine rupture Labor
20 h

Abruptio placentae Second stage
2.5 h

Placenta previa Precipitous labor Meconium in amniotic fluid Prolonged latent

Abnormal presentation phase

Multiple gestation Uterine tetany

Fetal weight 1500 g Induction of laborFetal weight
4000 g Operative forcepsFHR patterns indicating Vacuum extractioncompromise Nonreassuring FHR patterns

T ABLE 7-1

(Continued)

HIGH-RISK PREGNANCY 203

responsible for increased maternal and perinatal mortality and bidity Despite steady improvement, at least three quarters of ob-stetric deaths (9/100,000 births) and at least one half of newborndeaths (10/1000 births) in the United States are preventable

mor-PRENATAL CARE: A DIAGNOSTIC AND THERAPEUTIC PROGRAM

Good prenatal care is preventive medicine of a high order It vides an opportunity to identify the individual’s risk status and ap-propriately individualize care for each patient Moreover, it has been

pro-amply demonstrated that those gravidas who receive good prenatal

care materially improve both their own and their offspring’s chance

of successfully negotiating this most hazardous interval of life Maternal, fetal, or neonatal hazard often can be foretold by crit-ical assessment of the gravida’s history, physical examination, andantenatal course Dozens of factors during pregnancy, labor, deliv-ery, and the early puerperium suggest added risk; for example,unwanted pregnancy, ignorance, exposure to toxic products, and un-willingness or inability to obtain good early obstetric care relate tohigh-risk pregnancy Whatever the problem, prevention, early di-agnosis, and proper treatment will greatly reduce the perinatal mor-tality and morbidity rates Thus, most clinicians include these fac-tors in their plan for prenatal care (Chapter 5) and actively searchfor and treat them as the pregnancy progresses

Additionally, several risk scoring systems to predict jeopardy havebeen suggested Although risk scoring systems are not as sensitive or

Breech delivery General anesthesia

Prolapsed cord Abnormal maternal vitalFetal acidosis signs

Shoulder dystocia Fetal presentation not Maternal distress descending with labor

204 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

as specific as originally thought, they may provide a useful method

to ensure that most of the risk-producing states are screened in eachgestation

HISTORICAL SCREENING

Poverty, ignorance, substance abuse, and unwanted pregnancy are

sociologic conditions associated with high-risk pregnancy These

may take years to alleviate, and their solutions have little to do withmedicine For example, low socioeconomic and single marital sta-tus (in an adolescent) are two important obstetric high-risk factors.Although physicians cannot do much to remedy the underlyingproblem, proper diet, rest, social support, proper antenatal care, andgood patient cooperation can improve the prognosis of such an ado-lescent to approximate that of most middle-income gravidas Thus,

our purpose is to deal primarily with factors that can be influenced

by medical management and the currently available diagnostic and

therapeutic modalities

A uniform perinatal record is very useful to assist the physician

in evaluating high-risk pregnancy Some commercially availableforms may use risk lists, whereas others rate factors according totheir importance Whatever system is used, it must be applied as-siduously

MATERNAL AGE

The lowest rates of maternal and perinatal morbidity and mortalityoccur at maternal age 20–29 years Thus, younger and older womenare at greater risk

Adolescent pregnancy has a higher frequency of low birth weight infants, and in those younger than 16 years, there is increased risk

of pregnancy-induced hypertension Mothers age 35 or older are at

high risk, and those over 40 years are at extraordinary risk The

most common problems are increased chromosomal abnormalities,

chronic hypertension, pregnancy-induced hypertension, obesity, uterine leiomyomas, increased incidence of age-related medical problems (e.g., diabetes), and an increased risk of being delivered

by cesarean section The risk of trisomy is directly related to age,

rising from 0.9% at age 35–36 years to 7.8% at age 43–44 years.

Prenatal diagnosis screening questions (Table 7-2) should be asked

of each older gravida and the follow-up documented Starting thescreening as early as maternal age 32 has merit Women with a lowlevel of serum alpha-fetoprotein (AFP), regardless of age, should

HIGH-RISK PREGNANCY 205

T ABLE 7-2PRENA T AL DIAGNOSIS SCREENING QUESTIONS

Circle Appropriate

1 Will you be age 35 or older Yes No when the baby is due?

2 Have you or the baby’s father

or anyone in either of your

families ever had

a Down syndrome? Yes No

b Spina bifida or Yes Nomeningomyelocele

(open spine)?

(blood will not clot)?

d Muscular dystrophy? Yes No

3 Have you or the baby’s father Yes Nohad a child born dead or alive

with a birth defect not listed

in Question 2?

If yes, describe:

4 Do you or the baby’s father Yes Nohave any close relatives who

are mentally retarded?

If yes, list cause if known:

5 Do you or the baby’s father Yes No

or close relative in either of

your families have any

inherited genetic or

chromosomal disease or

disorder not listed above?

6 Have you or the spouse of Yes Nothis baby’s father in a

previous marriage had three

or more spontaneous

pregnancy losses?

7 Do you or the baby’s father Yes Nohave any close relatives

descended from Jewish

people who lived in Eastern

(Continued)

206 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

T ABLE 7-2

(Continued)

Circle Appropriate

Europe (Ashkenazi Jews)?

If yes, have either you or the Yes Nobaby’s father been screened for

Tay-Sachs disease?

If yes, indicate results and who screened:

8 If patient or spouse is African Yes No American: Have you or the

baby’s father or any close

relative been screened for

sickle cell trait and found to

be positive?

I have discussed with my doctor the above questionswhich are answered yes and understand that I am at

increased risk for:

and that it is usually possible to diagnose an affected fetus

by testing amniotic fluid at about 16 weeks of pregnancy orplacental tissue at an earlier time in pregnancy and I DONOT want the test

(Patient Signature) (Date)Patient wants amniocentesis and fetal diagnoses for:

Patient referred for further testing or counseling

In summary, it is important to ascertain the following Does the

patient, her husband, or their family have heritable disorders (seeTable 7-2)? What is the health of first-degree relatives (siblings,parents, and offspring), second-degree relatives (uncles, aunts,nephews, nieces, and grandparents), and third-degree relatives

(first cousins)? What are the probable reproductive outcomes? Isthere drug exposure (both husband and wife)? What are theparental ages (paternal risk 55)? What is the ethnic origin (be-

cause of enhanced risk of several disease states, e.g., Tay-Sachsdisease in Ashkenazi Jews,
-thalassemia in Italians and Greeks,

sickle cell anemia in African Americans, and -thalassemia in

Southeast Asians)?

OBSTETRIC HISTORY

The number of previous pregnancies is important To para 5, there

is increased chance of successful pregnancy However, after 5, therisk from uterine inertia, postpartum hemorrhage, placenta previa,and abruptio placenta begins an almost exponential increase A his-tory of infertility places a patient at increased risk because of agreater incidence of fetal wastage There is a correlation betweenthe outcome of previous pregnancies and what may happen to thecurrent pregnancy

Thus, the following obstetric historical findings signal risk:

in-duced hypertension, baby with known or suspected genetic der or congenital anomaly, and birth-damaged infant or infant re-quiring special neonatal care Other historical risk factors includeoperative deliveries (cesarean section, midforceps or breech ex-traction), prolonged labor or dystocia, severe psychiatric distur-bances associated with pregnancy, and closely spaced pregnancies(3 months)

disor-REPRODUCTIVE TRACT DISORDERS

Abnormalities of the reproductive tract cause at least 25% of

re-cidive reproductive losses Thus, a history of incompetent cervix,

septate uterus, bicornuate uterus, or uterine leiomyomas may warn

of pregnancy risk Other reproductive tract aberrations that may

place the pregnancy at risk because they can require therapy

dur-ing pregnancy include cervical dysplasia and ovarian tumors.

Should intervention be necessary, the safest time to perform gery is during the second trimester, when both post surgical abor-tion and preterm labor have the lowest incidence

sur-EXPOSURE TO FETOTOXIC AGENT

For discussion of the topic, see Chapter 5

208 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

MEDICAL COMPLICATIONS

OF PREGNANCY

Some of the systemic diseases creating risk in pregnancy include:

blood disorders (e.g., coagulopathy, sickle cell disease), cancer,

cere-bral aneurysms or tumors, chronic hypertension, connective tissue disease (e.g., systemic lupus erythematosus), diabetes mellitus, en- docrine ablation, epilepsy, gastrointestinal and liver disease, heart disease, pulmonary disease, renal disease (e.g., glomerulonephritis),

and thyroid disorders (both hyperthyroidism and hypothyroidism).

dis-WEIGHT

Ideal weight is necessarily predicated on height and body habitus,

and abnormalities of weight must be individualized Both

under-weight and overunder-weight signal risk for the perinate Moreover, the

maternal prepregnancy weight and gain during pregnancy are lated directly to birth weight The woman who weighs 100 pounds

re-(45 kg) when not pregnant has an increased chance of having anSGA infant Women who are obese for height have a greater chance

of gestational diabetes as well as pregnancy complicated by LGAbirth, dysfunctional labor, shoulder dystocia, and birth trauma Mor-bidly obese gravidas increase their risk even further

BLOOD PRESSURE

Hypertension poses risk to pregnancy and requires evaluation

(Chapter 13) Although occasional hypotension from orthostasis or

from the supine hypotensive syndrome is of concern, it is easilymanaged symptomatically.

BREASTS

When a mass is found, the usual breast cancer workup cannot be

delayed by the pregnancy.

HEART

Diastolic murmurs, systolic murmurs grade 3, and arrhythmias

al-ways require a medical evaluation

VASCULAR SYSTEM

Severe varicosities tend to thrombose during pregnancy (p 441).

PELVIC EVALUATION

Pelvic problems relating to risk include genital prolapse, fixation

of a retroflexed and retroverted uterus, uterine anomalies, uterineleiomyomata, cervical tumors, cervical laceration, cervical incom-petence, genital condylomata accuminata (which may cause neona-tal laryngeal papillomas), genital herpes, group B streptococcal in-fections, abnormalities of the ovaries, abnormalities of the uterinetubes, and abnormalities of the bony pelvis or pelvic capacity

A diagnosis and a plan of management for each of the

condi-tions placing the patient at risk may assist in enhancing outcome

COURSE OF PREGNANCY

ANTENATAL VISITS

Antenatal visits must be more frequent for high-risk than for

nor-mal obstetric patients to accurately appraise the pregnancy and tify and correct problems Antenatal visits also provide an oppor-tunity for education about problems, their solution, and counseling.The etiologies of many serious problems that develop duringpregnancy are reviewed elsewhere Thus, only the major categoriesare summarized here

iden-ABNORMAL VITAL SIGNS

The most frequent aberrations of vital signs signaling risk during nancy are abnormal weight or blood pressure As noted previously,

210 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

failure to gain weight during pregnancy often is associated with an SGA perinate, and excessive weight gain is associated with an LGA perinate Fever can trigger preterm labor and can injure the fetal

CNS Pregnancy-induced hypertension (PIH) is most often

indi-cated by a 140/90 blood pressure or a 30 mm Hg systolic or a

15 mm Hg diastolic rise Other symptoms of PIH include

pro-teinuria and significant edema (Chapter 13)

COMMON LABORATORY

ABNORMALITIES

The most common abnormal laboratory values during pregnancy

are urinary (bacteria, protein, or glucose) or hematologic cant bacteriuria (
100,000 bacteria/mL) places the patient at risk

Signifi-for pyelonephritis, premature rupture of membranes, and premature

onset of labor Diabetes mellitus (even if only gestational) is related

to a number of pregnancy risks (p 464) Moreover, gestational abetic mothers require follow-up after delivery because they are at

di-increased risk of developing chemical diabetes Hematologic risks, the most common being anemia and isoimmunization, are detailed

in Chapter 14

PROBLEMATIC SYMPTOMS

OR SIGNS

Symptoms or signs of greatest concern during the course of pregnancy

include vaginal bleeding, uterine growth out of proportion to dates,

and the untimely termination of pregnancy Uterine bleeding in early

or late pregnancy warns of jeopardy to the pregnancy (Chapters 10and 11) A discrepancy in uterine size for dates requires ultrasonic

scanning for explanation If the size is less than reasonable for dates,

it is due most frequently to an error in dates, an SGA fetus, a genital anomaly, or oligohydraminos If the uterus is larger than expected for dates, it most commonly indicates hydramnios, multiple gestation, fetal anomaly, an LGA fetus, or an error in dates Preterm

con-termination of pregnancy, with or without rupture of membranes, issecond only to congenital anomalies as a cause of morbidity and mor-tality Postterm pregnancy termination poses risks of uteroplacentalinsufficiency, meconium-containing amniotic fluid, and complicatedlabor or trauma during labor and delivery (from excessive size)

SURGERY DURING PREGNANCY

Although not increased by pregnancy, acute appendicitis is the most

common surgical emergency during gestation The major pregnancy

complications of acute appendicitis (similar to all abdominal

sur-gery) include premature delivery and peritonitis.

If all physical trauma (e.g., assault, motor vehicle accidents, and

falls) were categorized as surgical emergencies, trauma would headthe list The patient with significant physical trauma during preg-

nancy has a marked risk of abruptio placenta.

IMMUNIZATIONS DURING PREGNANCY

Current recommendations concerning immunizations during nancy are summarized in Table 7-3

preg-COURSE OF LABOR

Common problems during the course of labor include dystocia, tal distress, and meconium-stained amniotic fluid

fe-DYSTOCIA

Dystocia is abnormal or difficult labor It occurs in 10% of

nul-liparas and is less common in multiparas The etiology of dystocia

is typically ascribed to one or a combination of the 4 Ps (pelvis,passenger, powers, and placenta)

The most common pelvic abnormalities associated with

dysto-cia include bony size or configuration, birth canal soft tissue ration (e.g., congenital anomalies, scarring of the birth canal, con-

aber-glutination of the external cervix os, or massive condylomata

accuminata), and other reproductive organ neoplasia (e.g., cervical carcinoma, ovarian cyst, or uterine leiomyoma), including a dis-

tended bladder or bowel.

Uterine dystocia (i.e., uterine activity that does not elicit the normal

progress of labor) is referred to as an abnormality of the powers.

212 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

T ABLE 7-3RECOMMENDA TIONS FOR IMMUNIZA TIONS

DURING PREGNANCY

Cholera Comply only to meet

international travel requirements Hepatitis A Imunize gravida after

exposure Newborns of mothers who are incubating or ill shouldreceive 1 dose after birth Hepatitis B Newborn should receive

hyperimmune globulin soonafter delivery, followed byvaccination

Influenza Immunize gravida following

criteria recommended forgeneral population Measles Live virus vaccine during

pregnancy contraindicated ontheoretical grounds Pooled immune globulins forpostexposure prophylaxis Mumps Theoretically contraindicated

during pregnancy Plague Immunize only if there is

substantial infection risk Poliomyelitis Not routinely recommended but

mandatory in epidemics orwhen traveling to epidemicareas

Rabies Same as nonpregnant

Rubella Contraindicated (although

teratogenicity negligible infollow-up of thoseinadvertently given thevaccine)

Tetanus and diphtheria Give toxoid if no primary series

or no booster in 10 years Postexposure prophylaxis in unvaccinated with tetanusimmune globulin plus toxoid

Commonly, uterine dystocia includes hypertonic, hypotonic, or

dis-coordinate uterine activity, although lack of voluntary expulsive fort during the second stage of labor also may delay delivery

ef-ABNORMAL PLACENTAL

LOCATION

Abnormal placental location (e.g., placenta previa or low-lying

pos-terior implantation) decreases pelvic capacity by lying over thesacral promentory

PELVIC TYPES

As noted in Chapter 1, the female pelvis is classified into four majortypes, although various combinations may occur (Fig 7-1, Table 7-4)

The gynecoid pelvis is the most favorable for vaginal delivery

and is seen in
50% of women in the United States It is

charac-terized by oval inlet (transverse diameter slightly exceeds the teroposterior diameter), straight sidewalls, nonprominent ischialspines, a wide subpubic arch, and a concave sacrum

an-The android (male-like) pelvis is found in
33% of Caucasian

and 15% of African American women The android inlet is shaped, the pelvic sidewalls are convergent, the ischial spines areprominent, the subpubic arch is narrow, and the sacrum is inclinedanteriorly in its lower one third It is likely to be associated withpersistent occiput posterior position and deep transverse arrestdystocia

Typhoid Recommended if traveling to

endemic area Varicella Varicella-zoster immune

globulin for exposure Indicated for newborns whose mothers developed varicellawithin 4 days before or

2 days after delivery Yellow fever Postpone travel if possible but

immunize before travel tohigh-risk areas

T ABLE 7-3

(Continued)

Curved, averagelength

Medium width

Straight, divergent,

or convergent

Wedge-shaped or rounded trianglePosterior segmentwide, flat;

anterior narrow,pointed

Straight withforwardinclinationNarrow

Usually convergent

Anteroposterior ovoid with length

of anterior andposteriorsegmentsincreased Transverse diameterreducedNormally curvedbut long andnerrowWide, shallow

Straight

Transverse ovoid; increased transverse

AP diameter of bothsegments

Curved, short

Slightly narrowed

Straight or slightly divergent

TA BLE 7-4

PEL VIC TYPES a

Often straight

Shortened

Slightly curvedNarrowOften shortened

Straight or divergent

Increased

CurvedWideWide

aAfter Caldwell and Moloy.

FIGURE 7-1. Pelvic types White lines in the diagrams at right show the greatest diameters of the pelves at left.

216 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

The anthropoid pelvis is found in
20% of Caucasian women and

85% of African American women It is marked by an oval inlet (but

the anteroposterior diameter exceeds the transverse), the pelvic sidewalls diverge, and the sacrum is inclined posteriorly This type pelvis

is most likely to be associated with occiput posterior dystocia

The platypelloid pelvis is rare (3% of all women) and is

char-acterized by a wide transverse diameter of the inlet Inlet dystocia

is common because the fetal head cannot enter the true pelvis verse arrest may occur in the midpelvis because internal rotation iscompromised by unfavorable pelvic diameters

Trans-CRITICAL PELVIC MEASUREMENTS

Critical pelvic dimensions (for average-sized fetuses) include a agonal conjugate 12.5 cm, an obstetric conjugate (anteroposterior

di-of the inlet) 10 cm, and a transverse of the midpelvis of 9.5 cm (Table 7-5).

INLET CONTRACTURE

Inlet contracture can be expected if the anteroposterior is 10 cm

or the transverse is 12 cm (or both) This is suggested clinically

T ABLE 7-5MEASUREMENTS IN CLINICAL PEL VIMETR Y

Abnor mal

Va lue Nor mal (PossiblyMeasurement V alue Inadequate)

Biischial diameter (BI) 8 cm 8 cm

Posterior sagittal diameter 8–9.5 cm 8 cm

218 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

by one or more of the following: a floating vertex presentation atterm or in early labor, an inability to perform the Muller-Hillis ma-neuver (manually pushing the fetal head into the pelvis with gen-tle fundal pressure), presenting part not well applied to the cervix

in labor, an abnormal presentation (e.g., breech, transverse lie), cordprolapse, poor progress in labor, uterine dystocia, excessive mold-

ing of the fetal head, or caput succedaneum formation

Complica-tions include prolonged labor, prolonged rupture of the membranes,

and pathologic retraction ring at the junction of the lower uterinesegment and fundus (Bandl’s retraction ring, signifying impendinguterine rupture) Cesarean section usually is necessary for the trueinlet contracture

OUTLET CONTRACTURE

Isolated outlet dystocia is very rare, but this occurs if the

inter-tuberous diameter is not 8 cm or the sum of the intertuberous and the posterior sagittal diameter of the outlet is 15 cm.

com-verse malpositions Whereas these positions may occur normally,

their persistence is abnormal Occiput posterior is associated with

partial deflection of the fetal head and presentation of the largerposterior portion of the head (as opposed to the smaller anteriorportion) to the transverse of the midpelvis The diagnosis is made

by vaginal examination (confirmed by palpating the fetal ear) sistent occiput transverse is associated with pelvic dystocia, platy-pelloid or android pelves, or uterine dystocia Deep transverse arrestoccurs in the midpelvis and usually is due to an inadequate mid-pelvic diameter, as in an android pelvis

Per-Selection of proper treatment that will be the least traumatic tomother and perinate requires clinical acumen

Sinciput or brow presentations usually are transient fetal

pre-sentations with various degrees of deflection of the fetal head, whichhopefully convert to face or vertex as labor proceeds Thus, expec-tant management is the first recommendation Of course, fetopelvicdisproportion, uterine inertia and arrested progress, prematurity, andgrand multiparity may mandate intervention

Face presentation occurs in
0.2% of deliveries and is most

commonly associated with congenital malformations (e.g., cephaly), fetopelvic disproportion, prematurity, or grand multipar-ity Mentum posterior position, in all but very small prematures, isnot safely deliverable vaginally Delivery of some mentum anteriorpresentations is possible, but most require cesarean section

anen-Abnormal fetal lie is most commonly transverse or oblique and

occurs in
0.33% of deliveries (six times more frequent in

prema-ture births) Other causative associations include grand multiparity,

pelvic contracture, and abnormal placental implantation External

cephalic version during the third trimester is most useful in

con-version to a vertex One of the major risks is a 20 times increase in

cord prolapse with rupture of the membranes A compound

presen-tation occurs when the presenting part is accompanied by a

pro-lapsed extremity Gentle pinching of the digits may cause the fetus

to retract the extremity Should this and spontaneous restitution fail

to occur or if dystocia is also a problem, consider cesarean section

MACROSOMIA

Macrosomia, defined as fetal size 4500 g, occurs in 5%–6% of term deliveries, but is more frequent in pregnancies complicated by

diabetes (some 10%–23% of offspring are macrosomic)

Macroso-mia is associated with increased incidences of labor induction,

pro-longed labor, traumatic delivery, and shoulder dystocia.

Risk factors for macrosomia can be divided into four major

cate-gories: maternal diabetes (a 2- to 5-fold increase compared to abetic women), constitutional, postdates pregnancy (
41 weeks as-

nondi-sociated with 2- to 4 increase over 38–40 weeks), and nondiabetic,

220 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

nonconstitutional The constitutional risks (and amount of increased

risk) associated with macrosomia include: maternal weight
90 kg

(198 lb) at onset of pregnancy (11), previous macrosomic fetus

(10), maternal birth weight
8 lb (3), maternal weight gain of

20 kg during pregnancy (2)

Only recently has the importance of factors other than insulinand hyperglycemia in the creation of fetal somatic overgrowth be-come apparent Factors currently being investigated to explain fe-tal macrosomia in offspring of nondiabetic gravidas without con-stitutional factors include the following

Insulin-lik e Gr o wth F actors. These Include IGF-I, IGF-II, andinsulin growth factor binding protein-3 (IGFBP3) IGF-I is statisti-cally higher in the cord blood of large for gestational age (LGA)neonates when compared to average for gestational age (AGA) andappears to be an in utero growth promoter in infants of nondiabeticwomen IGF-II expression is associated with fetal somatic over-growth only when biallelic Cord blood IGFBP-3 is significantlyhigher in LGA compared to AGA Placental lactogen expresses ac-tion through regulation of the maternal and fetal beta-cell mass andfunction Elevated leptin is observed in asymmetric macrosomic in-fants of nondiabetic mothers

Syndr omes Associated with F etal Ov er gr o wth. In the somia associated with the Beckwith-Wiedemann syndrome, bial-lelic expression of IGF-II may be responsible However, causation

macro-in the majority of syndromes with somatic overgrowth remamacro-ins known The Sotos and Weaver syndromes are two examples, al-though they may be different only by locus or allele hetogeneity.These syndromes are characterized by macrosomia, advanced skele-tal age, characteristic patterns of facial and radiographic anomalies,and contractures Sotos syndrome is associated with a higher inci-dence of cancers The Simpson-Golabi-Behmel syndrome occurs inmales and is associated with macrosomia, a “coarse” face, and ahigh incidence of cardiac abnormalities Perlman syndrome is char-acterized by macrosomia, nephromegaly with renal dysplasia,Wilms’ tumor, crytorchidism, multiple facial anomalies, hydram-nios, and hypoglycemia The combination of congenital hypertri-chosis, osteochondrodysplasia, and cardiomegaly is emerging as anew genetic syndrome, and includes macrosomia as a portion of theclinical profile The combination of Sturge-Weber-Krabbe and Kippel-Trenaunay syndromes have been expressed by fetal macro-somia and hydramnios

un-Prediction of macrosomia for a given patient is difficult torical correlations are less than accurate in predictive value The

His-physical examination and fundal measurements may be influenced

by maternal habitus, imprecise calculations of gestational duration,multiple pregnancy, hydramnios, or uterine tumor Ultrasonographicmeasurements of both general obstetric patients and those at riskfor macrosomia are no more precise than clinical estimates.

The pregnancy suspected (or known) to be complicated by macrosomia is at risk Treatment involves both short- and long-term

active intervention in several groups Diabetics and gestational abetic women will have less macrosomia with rigorously controlledblood sugar levels and carefully timed deliveries (particularly inthose with fetus
90th percentile for age, but 4250 g) In glucose

di-intolerant patients with macrosomia (perhaps
4000, but decidedly

in
4250 g) an elective cesarean may be considered Earlier

de-livery in potential postterm pregnancies may prove useful Thosepatients who have previously had a large baby may have the birthweights decreased by elective labor induction, but this may not de-crease cesarean rates, shoulder dystocia, or brachial plexus injury

There is significant recurrence risk for gravidas who have had prior shoulder dystocia (14 , 1% increased to 14%) and traumatic birth

(3-fold increase) Should cesarean not be employed, patients in the

latter two categories should be aware of their increased risk withattempting vaginal birth

Those gravidas with uncomplicated history and prenatal coursebut with suspected macrosomic fetuses, have an increased incidence

of labor abnormalities and cesarean associated with elective tions Thus, the wisdom of elective induction for a 4000–4500 g fetushas been questioned Likewise, the suspicion of macrosomia may notwarrant cesarean delivery Alternatively, with macrosomia, theprogress of labor (measured both by contractions and cervical dilata-tion vs time) should be monitored closely Labor abnormalities (see

induc-p 223), a lengthened second stage (nullipara
2 h, multipara
1 h),

and arrest of descent (3+) should signal consideration for cesarean

ABNORMAL LABOR (POWERS)

Consider two components in evaluating labor: the contractions per

se and the cumulative effect of the contractions as determined by

the progress of labor

The evaluation of contractions requires an affirmative answer

to the following five questions

● Is there fundal dominance? The relative intensity of

contrac-tion normally is greater in the fundus than in the midporcontrac-tion

or lower uterine segment Absence of fundal dominance mayindicate lack of a uterine synchrony (as occurs with falselabor)

222 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

● Does the uterus relax between contractions? Normal

rest-ing tone is 12–15 mm Hg When it is increased without tocin stimulation, suspect abruptio placenta

oxy-● Is the average value of the intensity of contractions 24 mm Hg? In the active phase of labor, intrauterine pressure often

increases to 40–60 mm Hg

● Is the frequency of contractions about 3–5 min? With

nor-mal labor, the frequency of contractions progresses from oneevery 3–5 min to one every 2–3 min during the active phase

● Do the contractions last longer than 30 sec? The duration

of effective contractions is abnormal if they exceed 60 sec

ABNORMAL CONTRACTIONS

Hypotonic Dysfunction

Hypotonic dysfunction is characterized by contractions with

insuffi-cient force ( 25 mm Hg) or an irregular or infrequent rhythm or

both Hypotonic dysfunction is more common in nulligravidas during

FIGURE 7-2. Normal and dysfunctional uterine contraction types (After Jeffcoate.) Black, strong contraction; shaded, slight contraction; white, atonic areas.

the active phase of labor but may be associated with excessive dation, early administration of conduction anesthesia, and uterineoverdistention (e.g., multiple gestation, hydramnios) If there is nocontraindication (e.g., fetopelvic disproportion, multiple gestation,malpresentation, or allergy), hypotonic dysfunction responds well

se-to oxyse-tocin Figure 7-2 graphically depicts dysfunctional labor tractions

con-Hypertonic Dysfunction

Hypertonic and uncoordinated dysfunction often occur together and

may be accompanied by elevation of uterine resting tone, lack of

fundal dominance, and increased uterine pain Hypertonic

dysfunc-tion generally is associated with overzealous oxytocin use, abruptioplacenta, or fetopelvic disproportion Fetal compromise may be anassociation Hypertonic dysfunction may result in precipitate deliv-ery Treatment is problematic but often includes tocolysis, amylnitrate, cessation of oxytocin, or cesarean section (if indicated formalpresentation, fetopelvic disproportion, or fetal compromise) Thefetus subjected to hypertonic dysfunction is at increased risk of fetalcompromise, intracranial hemorrhage, or perinatal injury Lacera-tions of the birth canal also may result from rapid delivery

EVALUATION OF LABOR

Usually, dystocia is heralded by an abnormal labor pattern

Fig-ures 6-4 and 6-5 detail one method of assessment and describe thenormal course of labor Decreasing perinatal risk requires the recog-nition of aberrations of labor and proper intervention

Abnormal patterns of labor (Fig 6-6) include a prolonged latent

phase, a protracted active phase (dilatation), protracted descent, a prolonged deceleration phase, the secondary arrest of dilatation, or the arrest of descent In contrast, precipitate labor may also occur.

ABNORMAL LABOR PATTERNS

The prolonged latent phase begins with the onset of regular tions and ends at the beginning of the active phase of labor (3–4 cm

contrac-cervical dilatation) The average latent phase is
6 h for nulliparas

and
5 h for multiparas, with the upper limit of normal at 20 h for

nulliparas and 14 h for multiparas The usual causes of a prolonged

latent phase include excessive analgesics or analgesics tered too early in labor, conduction anesthesia performed before the active phase, an unfavorable cervix (e.g., a low Bishop score or scar-

adminis-ring), uterine dysfunction (e.g., weak, irregular, uncoordinated, or