Ruptur Uteri Dan Fetal Distress
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Transcript of Ruptur Uteri Dan Fetal Distress
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UTERINE RUPTURE
Williams Obstetrics 24th Edition (HAL 617 Chapter 31)
CLASSIFICATION
Uterine rupture typically is classified as either (1) complete when all layers of the uterine
wall are separated, or (2) incomplete when the uterine muscle is separated but the viscera
peritoneum is intact !ncomplete rupture is also commonly referred to as uterine
dehiscence "s e#pected, morbidity and mortality rates are appreciably $reater when
rupture is compleat %he $reatest ris& factor for either from of rupture is prior cesarean
delivery !n a review of all uterine rupture cases in 'ova cotia between 1** and 1+,
ieser and -as&ett (2..2) reported that 2 percent were in women with a prior cesarean
birth /olm$ren and associates (2.12) described 42 cases of rupture in women with a
prior hysterotomy Of these, 0 were in labor at the time of rupture
DIAGNOSIS
ro$ress of labor in women attemptin$ 3-" is similar to re$ular labor, and there is no
specific pattern that presa$es uterine rupture (5rasec&, 2.12 6 harper, 2.12b) -efore
hypovolemic shoc& deve&ops, symptoms and physical findin$s in women with uterine
rupture may appear bi7arre unless the possibility is &ept in mind 8or e#ample,
hemoperiteoneum from a ruptured uterus may result in diaphra$matic irritation with painreferred to the chest9directin$ one to a dia$nosis of pulmonary or amnionic fluid
embolism instead of uterine rupture %he most common si$n of uterine rupture is a
nonreassurin$ fetal heart rate pattern with variable heart rate decelerations that may
evolve into late decelerations and bradycardia as shown in 8i$ure 0194 ("merican
"cademy of ediatrics and "merican ole$e of Obstetricians and 5ynecolo$ists, 2.12)
!n 0 cases of such rupture durin$ a trial of labor, there were fetal si$ns in 24, maternal in
ei$ht, and both in three (/olm$ren, 2.12) 8ew women e#perience cessation of
contractions followin$ uterine rupture, and the use of intrauterine pressure catheters has
not been shown to assist reliably in the dia$nosis (:odri$ue7, 1*)
!n some women, the appeatance of uterine rupture is indentical to that of placental
abruption !n most, however, the is remar&ably little appreciable pain or tenderness "lso,
because most women in labor are treated for discomfort with either narcotics or epidural
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anal$esia, pain and tenderness may not be readily apparent %he condition usually
becomes evident bacause of fetal distress si$n and occasionally because of maternal
hypovolemia from concealed hemorrha$e
!f the fetal presentin$ part has entered the pelvis with labor, loss of station may be
detected by pelvic e#amination !f the fetus is pattly or totally e#truded from the uterine
rupture site, abdominal palpation or va$inal e#amination may be helpful to identify the
presentin$ part, which will have moved away from the pelvic inlet " firm contracted
uterus may at times be felt alon$side the fetus
DECISION-TO-DELIVER TI!E
With rupture and e#pulsion of the fetus into the peritoneal cavity, the chances for
intact fetal survival are dismal, and reported mortality rates ran$e from ;. to +; percent
Fetal condition depends on the degree to which the placental implantation remains
intact, although this can change within minutes.With rupture the only chance of fetal
survival is afforded by immediate delivery9most often by laparotomy9otherwisse, hypo#ia
is inevitable !f rupture is followed by immediate total placental separation, then very few
intact fetuses will be salva$ed %hus, even in the best of circumstnces, fetal salva$e will
be impaired %he Utah e#periences are instructive here (/olm$ren, 2.12)
Of the 0; laborin$ patients with a uterine rupture, the decision9to9delivery time was
< 1* minutes in 1+, and none of these infants had an adverse neurolo$ical outcome Of
the 1* born = 1* minutes from decision time, the three infants with lon$9term
neurolo$ical impairments were delivered at 01,4., and 42 minutes %here were no deaths,
thus severe neonatal neurolo$ical morbidity developed in * percent of these 0; women
with uterine rupture
!n a study usin$ the wedish -irth :e$istry, ac7marc7y& and collea$ues (2..+)
found that the ris& of neonatal death followin$ uterine rupture was ; percent9a .9fold
increase in ris& compared with pre$nancies not complicated by uterine ripture !n the
'etwor& study seven of the 114 uterine rupture9 percent9associated with a trial of labor
were complicated by the development of neonatal hypo#ic ischemic encephalopathy
(pon$,2..+)
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>aternal deaths from rupture are uncommon, 8or e#ample, of 2; milion women
who $ave birt in anada between 11 and 2..1, there were 1** cases of uterine
rupture, and four of these9.2 percent9resulted in maternal death (Wen, 2..;) !n other
re$ions of the world, however, maternal motality rates associated with uterine rupture are
much hi$her !n a report from rural !ndia, for e#ample, the maternal mortality rate
associated with uterine rupture was 0. percent (hatter?ee,2..+)
HSTERECTO! VERSUS REPAIR
With complete rupture durin$ a trial of labor, hysterectomy may be re@uired !n the
reports by >c>ahon (1) and >iller (1+) and their cowor&ers, 1. to 2. percent of
such women re@uired hysterectomy for hemostasis !n selected cases, however, suture
repair with uterine preservation may be performed heth (1*) described outcomes
from a series of women in whom repair of a uterine rupture was elected rather than
hysterectomy !n 2; instances, the repair was accompanied by tubal sterili7ation %hirteen
of the 41 mothers who did not have tubal sterili7ation had a total of 21 subse@uent
pre$nancies Uterine rupture recurred in four of these9appro#imately 2; persent Usta and
associates (2..+) identified 0+ women with a prior complete uterine rupture delivered
durin$ a 2;9year period in Aebanon /ysterectomy was performed in 11, and in the
remainin$ 2 women, the rupture was repaired %welve if these women had 24
subse@uent pre$nancies, one third of which were complicated by recurrent uterine
rupture !nanother study, however, women with a uterine dehiscence were not more li&ely
to have uterine rupture with a subse@uent pre$nancy (-aron,2.10b)
CO!PLICATIONS "ITH !ULTIPLE REPEAT CESAREAN DELIVERIES
-ecause of the concerns with attemptin$ a terial of labor9even in the women with
e#cellent criteria that forecast succesfull 3-"9most women in the United tates
Under$o elective repeat cesarean delivery %his choice in not without several si$nificant
maternal complication, and rates of these increase inwomen who have multiple repeat
operations %he incidences of some common complications for women with one prior
transverse cesarean delivery who under$o an elective repeat cesarean delivery were show
in tabele 0192 8inally, half of cesarean hysterectomies done at ar&land /ospital are in
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women with one or more prior cesarean deliveries (/ernande7, 2.10)
%he 'etwor& addressed issuer of increased morbidity in a cohort .f 0.,102 women
who had from one to si# repeat cesarean deliveries (ilver, 2..) %his report addressed a
list of morbidities, most of which increased as a trend sith increasin$ number of repeat
operations %he rates of some of the more common or serious complication are depicted
in fi$ure 019; !n addition to the ones shown, rates of bowel or bladder in?ury, admission
to an intensive care unit or ventilator therapy, and maternal mortality, as well as operative
and hospitali7ation len$th, showed si$nificantly increasin$ trends imilar results have
been reported by others ('isenblat, 2..6Usta,2..;) >ore difficult to @uantify are ris&s
for bowel obstructions and pelvic pain from peritoneal adhesive disease, both of which
inctease with each successive cesarean delivery ("ndolf, 2.1.6>an&uta, 2.10)
oo& and collea$ues (2.10) from the United in$dom Obstertic urveillance system
(UO) described adverse se@uelae of women with multiple cesarean deliveries
Outcomes of those under$oin$ a fifth or $reater operation were compared with those
from women havin$ a second throu$h fourth procedure %hose havin$ five or more
cesarean deliveries had si$nificantly increased rates if morbidity compared with rates in
women havin$ fewer than five procedures pecifically, the ma?or hemorrha$e rate
increased 1*9fold6 visceral dama$e, 1+9fold6 critical care admissions, 1;.fold6 and
delivery < 0+ wee&s, si#fold >uch of this morbidity was in the 1* percent who had
placenta previa or accrete syndromes (hap41p+) " percreta may invade the bladder
or other ad?acent structures With this, difficult resection carries an inordinately hi$h ris&
of hysterectomy, massive hemorrha$e with transfusion, and maternal maotality
STATE OF VAGINAL #IRTH AFTER CESAREAN-$%1&
%he Bbest answerC for a $iven women with a prior cesarean delivery in un&nown We
a$ree with scott (2.11) re$ardin$ a Bcommon9senseC approach %hus, the women9 and her
partner if she wishes9are encoura$ed to actively participate with her health9care provider
in the final decision after appropriate counselin$ 8or women who wish %OA" despite a
factor that increases their specific ris&, additions to the consent form are recommended
("merican olle$e of Obstetricians and 5ynecolo$iss, 2.10a) -pnanno and collea$ues
(2.11) have provided such an e#ample
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Williams Obstetrics 24th Edition (hal +.9+0 section 11 D chapter 41)
RUPTURE OF THE UTERUS
Uterine rupture may be primary, defined as accurrin$ in a previously intact or
unscarred unterus, or may be secondary and associated with a pree#istin$ myometrial
incision, in?ury, or anomaly ome of the etiolo$ies associated with uterine rupture are
presented in table 4190 !mportantly, the contribution of each of these underlyin$ causes
has chan$ed remar&ably durin$ the ppast ;. years pecifically, befor 1., when the
cesarean delivery rate was much lower than it is currently and when women of $reat
parity were numerous, primary uterine rupture predominated "s the incidence of
cesarean delivery increased and especially as a subse@uent trial of labor in these women
became prevalent throu$h the 1.s, uterine rupture throu$h the cesarean hysterotomy
scar became preeminent "s discussed in detail in hapter 01 (p1+) alon$ with
diminished enthusiasm for trial of labor in women with prior cesarean delivery, the two
types of rupture li&ely now have e@uivalent incidences !ndeed, in a 2.. study of 41
cases of uterine rupture from the /ospital orporation of "merica, half were in women
with a prior cesarean delivery (orreco,2..)
PREDISPOSING FACTORS AND CAUSES
!n addition to the pprior cesarean hysterotomy incision already discussed, ris& for
uterine rupture include other previous operations or manipulations thah traumati7e the
muometrium E#amples are uterine curetta$e or perforation, endometrial ablation,
myomectomy, or hysteroscopy (ieser, 2..26 elosi, 1+) !n the study by porreco and
collea$ues (2..) cited earlier, seven of 21 women with9out a prior cesarean delivery had
under$one prior uterine sur$ery
!n developed countries, the incidence of rupture was cited by $etahun and associates
(2.12) as 1 in 4*.. deliveriies %he fre@uency of primary rupture appro#imates 1 in
1.,... to 1;,... births (>iller, 1+6orreco, 2..) One reason is a decreased incidence
of women of $reat parity (>aymim, 116>iller, 1+) "nother is that e#cessive or
inappropriate unterine stimulation eith o#ytocin9previously a fre@uent cause9has mostly
disappeared "necdotally, however, we have encountered primary unterine rupture in a
disparate number of women in whom labor was induced with prosta$landin E1
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PATHOGENESIS
:upture of the previously intact uterus durin$ labor most often involver the thinned9
out lower uterine se$ment When the rent is in the immediate vicinity of the cervi#, it
free@uently e#tends trensversely or obli@uely Where the rent is in the portion of the
uterus ad?acent to the broad li$ament, the tear is usually lon$itudinal "lthou$h these
rears develop primarily in the lower uterine se$ment, it is not unusual for them to e#tend
upward into the active se$ment or downward throu$h the cervi# and into the va$ina
(fi$41910) !n some cases, the bladder may also be lacerated (:acha$an, 11) !f the
rupture is of sufficient si7e, the uterine contents will usually escape into the peritoneal
cavity !f the presentin$ fetal part is firmly en$a$ed, however, then only a portition of the
fetus may be e#truded from the uterus 8etal pro$nosis is lar$ely dependent on the de$ree
of placental separation and ma$nitude of maternal hemorrha$e and hypovolemia !n some
cases, the overlyin$ peritoneum remains intact, and this usually is accompanied by
hemorrha$e that e#tends into the broad li$ment to cause a lar$e retroperitoneal hematoma
with e#tensive blood loss
Occasionally, there is an inherent wea&ness in the myomatrium in which the rupture
ta&es place ome e#amples include anatomical anomaalies, adenomyosis, and
connectivetissue defects such as Ehlers9anlos syndrome ("rici, 2.106'i&olaou, 2.10)
!ANAGE!ENT AND OUTCO!ES
%he varied clinical presentations of uterine rupture and its mana$ement are discussed
in detail in chapter 01 (p1+)
!n the recent maternal mortality statistics from the centers for isease ontrol and
revention, uterine rupture accounted for 14 of deaths caused by hemorrha$e (-er$,
2.1.) >aternal morbidity includes hysterectomy that may be necessary to control
hemorrha$e %here is also considerably increased perinatal morbidity and mortality
associated with uterine rupture " ma?or concern is that survivin$ infants develop severe
neurolo$ical impairment (orreco, 2..)
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TRAU!ATIC UTERINE RUPTURE
"lthou$h the distended pre$nant uterus is surprisin$ly resistant to blunt trauma,
pre$nant women sustainin$ such trauma to the abdomen should be watched carefully, for
si$n of a ruptured uterus (hap4+, p;4) Even so, blunt trauma is more li&ely to cause
placental abruption as described subse@uently !n a study by miller and paul (1),
trauma accounted for only three cases of uterine rupture in more than 1;. women Other
causes of traumatic rupture that are uncommon today are those due to internal podalic
version and e#traction, difficult forceps delivery, breech e#traction, and unsual fetal
enlr$ement such as with hydrocephaly
TA#LE &1-3' Se *a+,e, Uter./e R+pt+re
ree#istin$ Uterine !n?ury or "nomaly Uterine in?ury or "bnormality incurred in currentre$nancy
S+r0er ./22./0 the etr.+ 4
esarean delivery or hysterotomy
reviously repaired uterine rupture
>yomectomy incision throu$h or the endometrium
eep cornual resection of interstitial fallopian tube
>etroplasty
C./*.5e/ta +ter./e tra+a 4
"bortion with instrumentation9sharp or suction
curette, sounds harp or blunt trauma9assaults, vehicular accidents,
bullets,&nives
ilent rupture in previous pre$nancy
C/0e/.ta 4
re$nancy in undeveloped uterine horn
efective tissue9>arfan or Ehlers9anlos yndrome
#ere 5e.2er 4
ersistent, !ntense, pontaneous contractions
Aabor stimulation9o#ytocin or prosta$landins
!ntraamnionic instillation9saline or prosta$landins
erforation by internal uterine pressure catheter
E#ternal trauma9sharp or blunt
E#ternal 3ersion
Uterine overdistention9hydramnios, multifetal pre$nancy
D+r./0 5e.2er 4 !nternal version second twin
ifficult forceps delivery
:apid tumultuous labor and delivery
-reech e#traction
8etal anomaly distendin$ lower se$ment
3i$orous uterine pressure durin$ delivery
ifficult manual removal of placenta
A*+.re5 4
lacental accrete syndromes
5estational trophoblastic neoplasia
"denomyosis
acculation of entrapped retroverted uterus
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REFERENCES
Williams Obstetrics F(edited bay) 85ary unnin$ham, enneth GAeveno, teven A
-loom, atherine H pon$, Godi ashe, -arbara A /offman, -rian >asey,
Geanne heffied924 th edition hal 1+ hapter 01 D hal +.9+0 section 11 D
chapter 41, 2.14)
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TA#EL 31-& Se Re*e/5at./, Pre,,./a S+*.et.e, C/*er/./0 a tr.a a ar t Attept V#AC
C+/,e./0 Fa*..t.e, Other
"merican olle$e of
obstetricians and 5ynecolo$ist
(2.10a)
ociety of
Obstetricians and $ynaeclo$ists
of canada (2..;)
:oyal olle$e of Obstetricians
and 5ynaecolo$ists (2..+)
Offter to most women with one
prior low9transverse incision6
consider for two prior low9
tranverse incisions
Offer to women with one prior
transverse low9se$ment cesarean
delivery6 with=1 prior then
3-" li&ely successful but
increased ris&s
iscuss 3-" option with women
with prior low9se$ment cesarean
delivery6 decision between
obstetrician and patient
afest with ability for
immediate cesrean delivery6
patients should be allowed to
accept increased ris& when not
available
hould deliver in hospital in
which timely cesarean delivery
is available6 appro#imate
timeframe o 0. minutes
uitable delivery suite with
continuous care and
monitorin$6immediate
cesarean delivery capability
'ot precluded6 twins,
macrosomia, prior lowvertical
or un&nown type of incision
O#ytocin or foley catheter
induction safe, but
prosta$landins should not be
used6macrosomia, diabetes,
postterm pre$nancy, twins are
not contraindications
aution with twins and
macrosomia
I cesarean delivery63-"I 3a$inal birth after cesarean
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-erief synopses of professional society $uidelines are shown in table 0194 5uidelines that tend to be more conservative are show
in table 019;
TA#LE 31-8' C/,er2at.2e G+.5e./e, t appra*h a tr.a ar 9./0 *e,area/ 5e.2er
F9 ACOG pra*t.*e 0+.5e./e,
E5+*at./ a/5 *+/,e./0
reconceptionally
rovide "O5 patient pamphletEarly durin$ prenatal care
evelop preliminary plan :evisit at least each trimester
-e willin$ to alter decision
/ave facilities availability
R.,: a,,e,,e/t
:eview previous operative note (s)
:eview relative and absolute contraindications
:econside ris& as pre$nancy pro$resses%read carefully J = 1 prior transverse , un&nown incision, twins, macrosomia
Lar a/5 5e.2er
autions for induction9unfavorable cervi#, hi$h station onsider ":O>
"void prosta$landins :espect o#ytocin9&now when to @uit-eware of abnormal labor pro$ress
:espect E8> pattern abnormalities
now when to abandon a trial of labor
"O5 I "merican olle$e of Obstetricians and 5ynecolo$ists6 ":O> I artificial rupture of membranes6 I esarean elivery 6
E8> I eleectronic fetal monitorin$
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Williams Obstetrics 24th Edition (hal 419;.. chapter 24)
FETAL DISTRESS
%he terms fetal distress and birth asphy#ia are to broad and va$ue to be applied
with any precision to clinical situations ( "merican colla$e of obstetricians and
$ynecolo$ists, 2..;) Uncertainty re$ardin$ the dia$nosis based on interpretation of
fetal hearth rate patterns has $iven rise to descriptions such as reassuring or non
rearssuring. %he terms Breassurin$ su$$ests a restoration of confidence by particular
pattern, whereas Bnonreassurin$C su$$ests inability to remove doubt %hese patterns
durin$ labor are dynamic K they can rapidly chan$e from reassurin$ to nonreassurin$
and viceversa !n this situation, obstetrician lose confidence or cannot assua$e doubts
about fetal condition These assessments are subjective clinical judgments that areinevitably subject to imperfection and must be recognized as such.
Pathph,.0
Why is the dia$nosis of fetal distress based on hearth rate patterns so tenuousL
One e#planation, is that these patterns are more a reflection of fetal physiolo$y than of
patholo$y hysiolo$ical control of hearth rate includes various interconnected
mechanisms that depend on blood flow ande o#y$enation >oreover, the activity of
these control mecanisms influenced by the pree#istin$ state of fetal o#y$enation, for
e#ample, as seen with chronic plasental insufficiency !mportantly, the fetus is
tethered by an umbilical cord, whereby blood flow is constanly in ?eopardy
>oreover, normar labor is a process of increasin$ acidemia ( ro$ers 1*) %hus,
normal labor is a process of repeated fetal hypo#ic events resultin$ inevitably in
academia
ut another way, and assumin$ that Basphy#iaC can be defined hypo#ia leadin$ to
acidemia, normal parturition is an as phy#iatin$ event for the fetus
D.a0/,.,
-ecause of the above uncertainties it follows that identifications of Bfetal
distressC based on fetal heart rate patterns is imprecise and controversial !t is well
&nown that e#perts in interpretations of these patterns of ten dissa$re with each order
!n fact, parer (1+), a stron$ advocate of electronic fetal heart rate monitorin$ and an
or$ani7er of the 1+ '!/ fetal monitorin$ wor&shop, li$ht heartedly compared
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the e#perts in attendance to marine i$uanas of the 5alapa$os !slands, to witJ Ball on
the same beach but facin$ different direntions and spittin$ at one another constantlyMC
"yres9de9ampos and collea$ues (1) investi$ated interobserver a$reement of
fetal heart rate pattern interpretation and found that a$reement Kor conversely,
disa$reementNwas related to whether the pattern was normal, suspicious, or
patholo$ical pecifically, e#perts a$reed on 2 percent of normal patterns, 42 percent
of suspicious patterns, and only 2; percent of patholo$ical pattens eith and
cowor&ers (1;) as&ed each of 1+ e#perts to review ;. tracin$s on two occasions, at
least 1 month apart "ppro#imately 2. percent chan$ed their own interpratations, and
appro#imately 2; percent did not a$ree with the interpretations of their colla$ues "nd
althou$h >urphy and associates (2..0) conclude that at least part of the interpretation
problem is due to a lac& of formali7ed education in "merica trainin$ pro$ram, this is
obviously only on a small modifier ut another way, how can the teacher enli$hten
the student if the teacher is uncertainL
Nat./a I/,t.t+te, Heat "r:,hp, Three-T.er Ca,,..*at./ S,te
%he '!/ (1+) held a succession of wor&shops in 1; and 1 to develop
standardi7ed and unambi$uous defitions of fetal heart rate (8/:) tarcin$s and
published recommendations for interpretin$ these patterns !n 2..*, a second
wor&shops was convened to reevaluate the 1+ recommendations and to clarify
terminolo$y (see table 2491) (>acones,2..*) " ma?or result was the recommendation
of a three9tier system for classification of 8/: patterns (table 2492) %he "merican
olle$e of Obstetricians and 5ynecolo$ist (2.10b) subse@uently recommended use of
this tiered system
" few studies have been done to assets the three9tiered systems Gac&son and
cowo&ers (2.11) studied 4*,444 women in labor and found that cate$ory ! (normal
8/:) patterns were observed durin$ labor in ; percent of tracin$s ate$ory !!
(indeterminate 8/:) patterns were found in *41 percent of tracin$s, and cate$ory !!!
(abnormal 8/:) patterns were seen in .1 percent (;4 women) >ost K*4 percent of
women Khad a mi# of cate$ories durin$ labor ahill and collea$ues (2.12)
retrospectively studied the incidence of umbilical cord academia (h +1.)
correlated with fetal heart rate characteristics durin$ the 0. minutes precedin$
delivery 'one of the three cate$ories demonstrated a si$nificant association with cord
blood academia %he "merican olle$e of Obstetricians and 5ynecolo$ist and the
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"merican "cademy of ediatrics (2.14) concluded that a cate$ory ! or !! tracin$ with
a ;9minutes "p$ar score = + or normal arterial blodd acid9base values was not
consistent with an acute hypo#ic9ischemic event
holapur&ar (2.12) also challen$ed the validity of the three tier system because
most abnormal fetal rate patterns fall into the inderterminate cate$ory !!, that is, one
for which no definite mana$ement recommendations can be made !t was further
su$$ested that this resulted from most fetal heart rate decelerations bein$
inappropriately classified as variable decelerations due to cord compression
aree and in$ (2.1.) compared the current situation in the United tates with
that of other countries in which a consensus on classification and mana$ement has
been reached by a number of professional societies ome of these include the :oyal
olle$e of Obstetricians and 5ynecolo$ist, the ociety of Obstetricians and
5ynecolo$ists of anada, the :oyal "ustralian and 'ew Pealand olle$e of
Obstetricians and 5ynecolo$ists and the Gapan ociety of Obstetricians and
5ynecolo$y arer and in$ (2.1.) further comment that the '!/ three9tier
system is inadfe@uate because cate$ory !!Ninderteminate 8/:Nconsist of a Bvast
hetero$enous mi#ture of patternsC that prevent development of a mana$ement
strate$y eter and !&eda (2..+) had previously proposed a color9coded five9tier
system for both 8/: interpretation and mana$ement %here have been two reports
comparin$ the five9tier and three9tier systems -annerman and associates (2.11)
found that the two system were similar in fetal heart rate interpretations for tracin$
that were either very normal or very abnormal oletta and cowo&ers (2.12) found
that the five9tier system had better sensitivity than the three9tier system !t is apparent
that, after ;. years of continuous electronic fetal heart rate monitorin$ use, there is not
a consensus on interpretation and mana$ement recommendations for 8/: patterns
(arer,2.11)
Tae $&'$ Three-t.er eta heart rate ./terpretat./ ,,te
Cate0r I-NOR!AL
!nclude all of the followin$J
• -aseline rate J 11. K 1. bpm
• -aseline 8/: variability J moderate
• Aate or variable decelerations J absent
•Early decelerations J present or absent
• "ccelerations J present or absent
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ate$ory !! K !'E%E:>!'"%E
!nclude all 8/: tracin$s not cate$ori7ed as cate$ory ! or !!!
ate$ory !! tracin$s may represent an appreciable fraction of those encountered in
clinical care E#amples include any of the followin$J
-aseline rate• -radycardia not accompanied by absent baseline variability
• %achycardia
-aseline 8/: 3":!"-!A!%H
• >inimal baseline variability
• "bsent baseline variability not accompanied by recurrent decelerations
• >ar&ed baseline variability
"EAE%"%!O'
• "bsence of induced accelerations after fetal stimulation periodic or episodic
decelerations
• :ecurrent variable decelerations accompanied by minimal moderate baseline
variability
• rolon$ed deceleration Q min 2 but < 1. min
• :ecurrent late decelerations with moderate baseline variability
• 3ariable decelerations with other characterististic, such as slow return to
baseline, Bovershoot,C or BshouldersC
ate$ory !!!
!nclude either J
• "bsent baseline 8/: variability and any of the followin$ recurrent late
decelerations, recurrent variable decelerations, bradycardia
• inuisoidal pattern
-pm I beats per minute 6 8/: I fetal heart rate
8rom >acones, 2..*, with permission
!e*/.+ ./ the a/.t.* +.5
Obstetrical teachin$ throu$hout the past century has included the concept that
meconium passa$e is a potential warnin$ of fetal asphy#ia !n 1.0, G Whitrid$e
Williams observed and attributed meconium passa$e to Brela#ation of the sphincter
ani muscle induced by faulty aeration of the (fetal) bloodC Even so, obstetricians have
also lon$ reali7ed that the detection of meconium durin$ labor is problematic in the
prediction of fetal distress or asphy#ia !n their review, at7 and -owes (12)
emphasi7ed the pro$nostic uncertainty of meconium by referrin$ to the topic as a
Bmur&y sub?ectC !ndeed, althou$h 12 tp 22 percent of labors are complicated by
meconium, only a few are lin&ed to infant mortality !n an investi$ation from ar&land
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/ospital, meconium was found to be a Blow9ris&C obstetrical ha7ard because the
perinatal mortality rate attribubutable to meconium was ! death per 1... live births
('athan,14)
%he theories have been su$$ested to e#plain fetal passa$e of meconium and in
part may e#plain the tenuous conection between its detection and infant mortality
8irst, the phatolo$ical e#planation proposes that fetuses pass meconium in response to
hypo#ia and that meconium therefore si$nals fetal crompomise (wal&er, 1;0)
econd, the physiolo$ical e#planation is that in utero passa$e of meconium represents
normal $astrointestinal tract maturation under neural control (>athews, 1+) " final
theory posits that meconium passa$e follows va$al stimulation from common but
transient umbilical cord entrapment with resultant increased bowel peristalsis
(/on,11) %hus, meconium release may represent physiolo$ical processes
:amin and associates (1) studied almost *... pre$nancies with meconium
stained amniotic fluid delivered at ar&land /ospital >econium aspiration ayndrome
was si$nificantly associated with fetal academia at birth Other si$nificant correlates
of aspiration included cesarean delivery, forceps to e#pedite delivery, intrapartum
heart rate abnormalities, depressed ap$ar scores, and need for assisted ventilation at
delivery "nalysis of the type of fetal academia based on umbilical blood $ases
su$$ested that the fetal compromise associated with meconium aspiration syndrome
was an acute event %his is because most academic fetuses had abnormally increased
O2 values rather than a pure metabolic academia
awes and cowor&ers (1+2) observed that such hypercarbia in fetal lambs
induces $aspin$ and resultant increased amnionis fluid inhalation Govanovic and
'$uyen (1*) observed that meconium $asped into the fetal lun$s caused aspiration
syndrome only in asphy#iated animals :amin and collea$ues (1) hypothesi7ed
that the pathophysiolo$y of meconium aspiration syndrome includes, but is not
limited to, fetal hypercarbia, which stimulates fetal respiration leadin$ to aspiration of
meconium into alveoli Aun$ parenchymal in?ury is secondary to academia K induced
alveolar cell dama$e !n this phatophysiolo$ical scenario, meconium in amniotic fluid
is a fetal environmental ha7ard rather than a mar&er of pree#istent compromise %his
proposed pathophysiolo$ical se@uence is not all inclusive, because is does not account
for appro#imately half of the cases of meconium aspiration syndrome in which the
fetus was not academic at birth
%hus, it was concluded that the hi$h incidence of meconium observed in the
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amniotic fluid durin$ labor often represents fetal passa$e of $astrointestinal contents
in con?unction with normal physiolo$ical processes "lthou$th normal, such
meconium becomes an environmental ha7ard when fetal academia supervenes
!mportantly, such academia occurs acutely, and therefore meconium aspiration is
unpredictable and li&ely unpreventable >oreover, 5reenwood and collea$ues (2..0)
showed that clear amniotic fluid was also a poor predictor !n a prospective study of
*04 women with clear amniotic fluid, they found that clear fluid was an unreliable
si$n of fetal well9bein$
5rowin$ evidence indicates that many infants with meconium aspiration
syndrome have suffered chronic hypo#ia before birth (5hidini,2..1) -lac&well and
associates (2..1) found that .R of infants dia$nosed with meconium aspiration
syndrome had umbilical artery blood / Q +,2., implyin$ that the syndrome was
unrelated to the neonatal condition at delivery imilary, mar&ers of cronic hypo#ia,
such as fetal arythropoietin levels and nucleated red blood cell counts in newborn
infants, su$$est that chronic hypo#ia is involved in many meconium aspiration
syondrome case (ollber$, 2..1J Ga7ayeri,2...)
!n the recent past, routine obstetrical mana$ement of a newborn with meconium9
stained amniotic fluid included intrapartum suctionin$ of the oropharyn# and
nasopharyn# 5uidelines from the "merican "cademia of ediatric and the "merican
olle$e of Obstetricians and 5ynecolo$ists, however, recommend that such infants no
lon$er routinely receive intrapartum suctionin$ because it does not prevent meconium
aspiration syndrome (eelman,2.1.) "s discusses in chapter 02 (2), if the infant is
depressed, the trachea is intubated, and meconium suctioned from beneath the $lottis
!f the newborn is vi$orous, defined as havin$ stron$ respiratory efforts, $ood muscle
tone, and a heart rate = 1.. bpm, then tracheal suction is not necessary and may in?ure
the vocal cords
!ANAGE!ENT OPTIONS
%he principal mana$ement options for si$nificantly variable fetal heart rate
patterns consist of correctin$ any fetal insult, if possible >easure su$$ested by the
"merican olla$e of Obstetritians and 5ynecolo$ists (2.10b,c) are listed in table 249
0 >ovin$ the mother to the lateral position, correctin$ maternal hypotension caused
by re$ional anal$esia, and discontinuin$ o#ytocin serve to improve uteroplasental
paerfusion E#amination is done to e#clude prolapsed cord or impendin$ delivery
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impson and ?ames (2..;) assessed benefits of three maneuvers in ;2 women with
fetal o#y$en saturation sensors already in place %he used intravenous hydration K ;..
to 1... ml of lactated :in$er solution $iven over 2. minutes J lateral versus supine
position J and usin$ a nonrebreathin$ mas& that administered supplemental o#y$en at
1. AFmin Each of these maneuvers si$nificantly increased fetal o#y$en saturation
levels, althou$h the increments were small
TOCOLSIS
" sin$le intravenous or subcutaneous in?ection of .,2; m$ of terbutaline sulfate
$iven to rela# the uterus has been described as a tempori7in$ maneuver in the
mana$ement of nonreassurin$ fetal heart rate patterns durin$ labor %he rationale is
that inhibition of uterine contractions mi$ht improve fetal o#y$enation, thus achievin$
in utero resuscitation oo& and spinnato (14) described their e#perience durin$ 1.
years with tertabuline tocolysis for fetal resuscitation in 0* pre$nancies uch
resuscitation improved fetal scalp blood p/ values, althou$h all fetuses underwent
cesarean delivery %hese investi$ators concluded that althou$h the studies were small
and rarely randomi7ed, most reported favorable results with terbutaline tocolysis for
nonreasurin$ patterns mall intravenous doses of nitro$lycerin K . to 1*. S$ K also
have been reported to be beneficial ( mercier, 1+) %he "merican olla$e of
Obstetricians and 5yneclolo$ist (2.10b) has concluded that there is insufficient
evidence to recommend tocolysis for noreassurin$ fetal heart rate patterns
A!NIOINFUSION
5abbe and cowor&ers (1+) showed in mon&eys that removal of amniotic fluid
produced variable decelerations and that decelerations and that replenishment of fluid
with saline reliaeved the decelerations >iya7a&i and taylor (1*0) infused saline
throu$h an intrauterine pressure catcheter in laborin$ women who had either variable
decelerations or prolon$ed decelarations attributed to cord entrapment uch therapy
improved the harth rate pattern in half of the women who had either variable
decelerations or prolon$ed decelerations attributed to cord entrapment uch theraphy
improved the heart rate pattern in half of the women studied Aater, >iya7a&i and
'evare7 (1*;) randomly assi$ned nulliparous women in labor with cord
compression patterns and found that those who werw treated with amnioinfusion
re@uired cesarean delivery for fetal distress less often
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-ased on many of these early reports, transva$inal amnioinfusion has been
e#tended into three clinical areas %hese include J (1) treatment of variable or
prolon$ed decelerations, (2) prophyla#is for women with oli$ohydramnions, as with
prolon$ed ruptured membranes, and (0) attempts to dilute or wash out thic&
meconium (hap00,p0*)
>any different amnioinfusion protocols have been reported, but most include a
;.. K to *.. >l bolus of warmed normal saline followed by a continuous infusion of
a appro#imately 0 >l per minute (Owen, 1. Jressman, 1) !n another study,
:inehart and collea$ues (2...) randomly $ave a ;.. >l bolus of normal saline at
room temperature alone or ;.. >l bolus plus continuous infusion of 0 >l per minute
%heir study included ; women with variable decelerations, and the investi$ators
found neither method to be superior Wenstrom and associates (1;) surveyed use of
amnioinfusion in teachin$ hospitals in the 1* centers surveyed, and it was estimated
that 0 to 4 percent of all women delivered at these centers received such infusion
otential complications of amnioinfusion are summari7ed in table 2494
Tae $&-& Cp.*at./, A,,*.ate5 ".th A/../+,./ Fr a S+r2e 1;6
O,tetr.*a U/.t,'
CO!PLICATION CENTERS N'(
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and 5ynecolo$ists (2.10a) recommends considerations of amnioinfusion with
persistent variable decelerations
PROPHLACTIC A!NIOINFUSION FOR OLIOGOHDRA!NIOS
"mnioinfusion in women with oli$ohydramnios has been used prophylactically
to avoid intrapartum fetal heart rate pattern from cord occlusion 'a$eotte and
cowo&ers (11) found that this resulted in si$nificantly decreased fre@uency and
severity of variable decelarations in labor /owefer, the cesarean delivery rate or
condition of term infants was not improved !n a randomi7ed investi$ation, >acri and
collea$ues (12) studied prophylactic amnioinfusion in 1+. term and postterm
pre$nancies complicated by both thic& meconium and oli$ohydramnios
"mnioinfusion si$nificantly reduced cesarean delivery rates for fetal distress and
meconium aspiration syndrome !n contrast, O$undipe and associates (14)
randomly assi$ned 11 term pre$nancies with an amnionic fluid inde# < ; cm to
receive prophylactic amnioinfusion or standard obstetrical care %here were no
si$nificant differences in overall cesarean delivery rates, delivery rates for fetal
distress, or umbilical cord acid Kbase studies
A!NIOINFUSION FOR !ECONICU! =STAINED A!NIONIC FLUID
ierce and associates (2...) summari7ed the result of 10 prospective trials of
intrapartum amnioinfusion in 124 women with moderate to thic& meconium9stained
fluid !nfants born to women treated by amnioinfusion were si$nificantly less li&ely to
have meconium below the vocal cords and were lessli&ely to develop meconium
aspiration syndrome than infants born to women not under$oin$ amnioinfusion %he
cesarean delivery rate was also lower in the amnioinfusion $oup imilar result were
reported by :athore and cowo&ers (2..2) !n contrast, several investi$ators were not
supportive of amnioinfusion for meconium stainin$ 8or e#ample, Usta and associates
(1;) reported that amnioinfusion was not feasible in half of women with moderate
or thic& meconium who were randomi7ed to this treatment %hese investi$ators were
unable to demonstrate any improvement in neonatal outcomes pon$ and cowo&ers
(14) also concluded that althou$h prophylactic amnioinfusion did dilute meconium,
it did not improve perinatal outcome Aast, 8raser and collea$ues (2..;) randomi7ed
amnioinfusion in 1* women with thic& meconium stainin$ of the amnionic fluid in
labor and found no benefits -ecause of these findin$s, the "mericans olle$e of
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Obstetricians and 5ynecolists (2.12a,2.10c) does not recommended amnioinfusion to
dilute meconium9stained amnionic fluid "ccordin$ to Tu and cowo&ers (2..+), in
areas lac&in$ continuous monitorin$, amnioinfusion may be used to lower the
incidence of meconium aspiration syndrome
FETAL HEART RATE PATTERNS AND #RAIN DA!AGE
"ttemps to correlate fetal heart rate patterns with brain dam$e have been based
primarily on studies of infants identified as a result of medicole$al actions helan and
"hn (14) reported that amon$ 4* fetuses later found to be neurolo$ically impaired,
a persistent nonreactive fetal heart rate tracin$ was already present at the time of
admission in +. percent %hey concluded that fetal neurolo$ical in?ury occurred
predominately before arrival to the hospital When they loo&ed retrospectively at heart
rate patterns in 2. brain9dama$ed infants, they concluded that there was not a sin$le
uni@ue pattern associated with fetal neurolo$ical in?ury ("hn, 1) 5raham and
associated (2..) reviewed the world literature published between 1 and 2.. on
the effect of fetal heart rate monitorin$ to prevent perinatal brain in?ury and found no
benefit
E>PERI!ENTAL EVIDENCE
8etal heart rate patterns necessary for perinatal brain dama$e have been studied in
e#perimental animals >yers (1+2) describe the effects of complete and partial
asphy#ia omplete asphy#ia was produced by total occlusion of umbilical blood flow
that led to prolon$ed deceleration (fi$ 24901) 8etal arterial h did not drop to +.
until appro#imately *minutes after complete cessation of o#y$enation and umbilical
flow "t least 1. minutes of such prolon$ed deceleration was re@uired before these
was evidence of brain dama$e in survivin$ fetuses
>yers (1+2) also produced partial asphy#ia in rhesus mon&eys by impedin$
maternal aortic blood flow %his resulted in late decelerations due to uterine and
placental hypoperfusion /e observed that several hours of these late decelerations did
not dama$e the fetal brain unless the h fell bellow +. !nded, "damsons and >yers
(1++) reported subse@uently that late decelerations were a mar&er of partial asphy#ia
lon$ before brain dama$e occurred
%he most common fetal heart rate pattern durin$ laborNdue to umbilical cord
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electronic monitorin$ were bein$ voiced from the Office O8 %echnolo$y "ssesment,
the United tates on$ress, and the enters for isease ontrol and revention
-anta and %hac&er (2..2) reviewed 2; years of the controversy on the benefits, or
lac& thereof, of electronic fetal monitorin$ Usin$ the ochrane atabase, "lfirevic
and collea$ues (2.10) reviewed 10 randomi7ed trials involvin$ more than 0+,...
women %hey concluded that electronic fetal monitorin$ in increased the rate of
cesarean and operative va$inal deliveries but produced no declines in rates of
perinatal mortality, neonatal, sei7ures, or cerebral palsy 5rimes and eipert (2.1.)
wrote a urrent ommentary on electronic fetal monitorin$ in Obstetrics and
5ynecolo$y %hey summari7ed that such monitorin$, althou$ht it has been used in *;
percent of the almost 4 million annual births in the United tates, has failed as a
public health screenin$ pro$ram %hey noted that the positive predictive value of
electronic fetal monitorin$ for fetal death in labor or cerebral palsy is near 7eroN
meanin$ that Balmost every positive test result is wron$C
%here have been two recent attempts to study the epidemiolo$ical effect of fetal
monitorin$ in the United tates, each usin$ national vital statistics of births lin&ed to
infant deaths hen and cowo&ers (2.11) used 2..4 data on 1,+02,211 sin$leton live
births, * percent of which underwent electronic fetal monitorin$ %hey reported that
monitorin$ increased operative delivery rates but decrease early neonatal mortality
rates %his benefits was $estational a$e dependent, however, and the hi$hest impact
was seen in peterm fetuses >ost recently, "nanth and collea$ues (2.10) reported a
similar but lar$er epidemiolo$ical study usin$ United tates birth certificate data
lin&ed with infant death certificate %hey studied ;+,*0,2; nonanomalous sin$leton
livebirths born between 1. and 2..4 %he temporal increase in fetal monitorin$ use
between 1. and 2..4 was associated with a decline in neonatal mortality rates,
especially in peterm $estations !n an accompanyin$ editorial, :esni& (2.10)
cautioned that an eoidemiolo$ical association between fetal monitorin$ and reduced
neonatal death does not establish causation /e su$$ested that the limitations of the
study by "nanth Bshould ma&e the reader s&eptical of the findin$sC /e opined that
the electronical fetal monitorin$ debate Boes on and on and onC "nd it does
indeed
PAR?LAND HOSPITAL E>PERIENCE4 SELECTIVE VERSUS UNIVERSAL
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!ONITORING
!n ?uly 1*2, an investi$ation be$an at ar&land /ospital to ascertain whether all
women in labor should under$o electronic monitorin$ (Aevono, 1*) !n alternatin$
months, universal electronic monitorin$ was rotated with selective heart rate mo
nitorin$, which was the prevailin$ practice urin$ the 0 years investi$ation, 1+, 41.
labor were mana$ed usin$ universal electronic monitorin$, and these outcomes were
compared with a similar9si7ed cohort of women selectively monitored electronically
'o si$nificant differences were found in any perinatal outcomes %here was a small
but si$nificant increase in the cesarean delivery rate for fetal distress associated with
universal monitorin$ %hus increase application of electronic monitorin$ at par&lamd
hospital did not improve perinatal results, but it sli$htly increased the fre@uency of
cesarean delivery for fetal distress
CURRENT RECO!!ENDATIONS
%he methods most commonly used for intrapartum fetal heart monitorin$ include
auscultation with a fetal stethoscope or a oppler ultrasound device, or continuous
electronic monitorin$ of the heart and uterine contractions 'o scientific evidence has
identified the most effective method, includin$ the fre@uency or duration of fetal
surveillance that ensures optimum result ummari7ed in %able 249; are the
recommendations of the "merica "cademy of ediatrics and the "merican olle$e of
obstetricians and 5ynecolo$ists (2.12) !ntermittent auscultation or continuous
electronic monitorin$ is considered an acceptable method of intrapartum surveillance
in both low9 and hi$h9 ris& pre$nancies %he recommended interval between chec&in$
the heart rate, however, is lon$er in the uncomplicated pre$nancy When auscultation
and for . seconds !t also recommended that a 19to1 nurse9patient ratio be used if
auscultation is employed %he position ta&en by the "merican olle$e of
Obstetricians and 5ynecolo$ists (2.10b) in their ractice -ulletin, however, is
somewhat different While ac&nowled$in$ that the available data do not show a clear
benefit for the use of electronic monitorin$ over intermittent auscultation, the
commite recommends limitin$ use of auscultation to low ris& pre$nancies and further
recommends recordin$ the fetal heart rate every 1; minutes in active first sta$e labor
and every ; minutes in the second sta$e
S+r2e.a/*e L9 r.,: pre0/a/*.e, H.0h r.,: pre0/a/*.e,
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A**eptae eth5,
!ntermitten auscultation
ontinuous electronic
monitorin$ (internal or
e#ternal)
Hes
Hes
Hes a
Hes b
E2a+at./ ./ter2a,
8irst9sta$e labor (active)
econd9sta$e labor
0. min
1; min
1; min a,b
; min a,c
a9 predurin$, ferably before, and after a uterine contraction
b9 includes tracin$ evaluation and chartin$ at least every 1; min
c9 tracin$ should be evaluated at least every ; min
form the "merican "cademy of ediatrics and the "merican olla$e of Obtetricians
and $ynecolo$ist, 2.12
INTRAPARTU! SURVEILLANCE OF UTERINE ACTIVIT
"nalysis of electronically measured uterine activity permits some $eneralities
concernin$ the relationship of certain contraction patterns to labor outcome %here is
considerable normal variation, however, and caution must be e#ercised before ?ud$in$
true labor or its absence solely from a monitor tracin$ Uterine muscle effiociency to
effect delivery varies $reatly %o use an analo$y, 1..9meter sprinters all have the same
muscle $roups yet cross the finish line at different times
INTERNAL UTERINE PRESSURE !ONITORING
"mniotic fluid pressure is measured between and durin$ contraction by a fluid K
filled plastic catheter with its distal tiplocated above the presentin$ part (8i$24902)
%he chateter is connected to a strain K $au$e pressure sensor ad?usted to the same
level as the chateter tip in uterus %he amplified electrical si$nal produced in the strain
$au$e by variation in pressure within the fluid system is recored on a calibrated
movin$ paper strip simultaneously with the fetal heart rate recordin$ ( see fi$249)
!ntrauterine pressure chateters are now avaible that have the pressure sensor in the
chatete tip, which obviates the need for the fluid column
E>TERNAL !ONITORING
Uterine contraction can be measured by a displacement transducer in which the
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transducer button, or J Bplun$erC, is held a$ainst the abdominal wall "s the uterus
contracts, the button moves in proportion to the stren$th of the contraction %his
movement is convered into a measurable electrical si$nal that indicated the relative
intensity of the contraction !t has $enerally been accepted to not $ive an accurate
measure of intensity -a&&er and associates (2.1.) performed a randomi7ed trial
comparin$ internal versus e#ternal monitorin$ of uterine contractions in 14; women
%he two methods were e@uivalent in terms of operative deliveries and neonatal
outcomes
PATTERNS OF UTERINE ACTIVIT
aldeyro9barcia and oseiro (1.), from >ontevideo, Uru$uay, were pioneers
who have done much to elucidate the pattern of spontaneous uterine activity
throu$hout pre$nancy ontractile waves of uterine activity werw usually measured
usin$ intraamniotic pressure catheters -ut early in their studies, as many four
simultaneous intramiometrial microballons were also used to record uterine pressure
%hese investi$ators also introduced the concept of >ontevideo units to define uterine
activity (hap 20,pJ 4;*) -y this definition, uterine performance is the product of the
intensity K increased uterine pressure above baseline tone of a contraction in mm/$
multiplied by contraction fre@uency per 1. minutes 8or e#ample, three contractions
in 1. minutes, each of ;. nn /$ intensity, would e@ual 1;. >ontevideo units
urin$ the first 0. wee&s of pre$nancy,uterine activity is comparatively
@uiescent ontraction are seldom $reater than 2. mm /$ "nd these have been
e@uated with those first described in 1*+2 by Gohn -ra#ton /ic&s Uterine activity
increase $radually after 0. wee&s, and it is noteworthy that these -ra#ton /ic&s
ontractions also increase in intensity and fre@uency 8urther increases in uterine
activity are typical of the last wee&s of pre$nancy, termed prelabor urin$ this phase
%he cervi# ripens (hap21J41.)
"ccordin$ %o aldeyro K -arcia and oseiro (1.), clinical labor usually
commences when uterine activity reaches values between *. ande 12. >ontevideo
units %his translates into appro#imately three contractions of 4. mm /$ every 1.
minutes !mportantly, there is not clear K cut division between prelabor and labor, but
rather a $radual and pro$ressive transition
urin$ first9sta$e labor, uterine contarctions increase pro$ressively in intensity
from appro#imately 2; mm /$ at commencement of labor to ;. mm /$ at the end Et
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the same time, fre@uency increases from there to five contractions per 1. minutes, and
uterine baseline tone from * to 2. mm /$ Uterine activity further increases durin$
second K sta$e labor, aided by maternal pushin$ !ndeed, contractions .f *. to 1..
mm/$ are typical and occur as fre@uently as five to si# per 1. minutes !nterestin$ly,
the duration of uterine contractions K . to *. second K does not increase appreciably
from early active labor throu$h the second sta$e (-a&&er,2..+J ontonnier,1+;)
resumably, this duration constanly serves fetal repiratory $as e#chan$e urin$ a
uterine contarctions, as the intrauterine pressure e#ceeds that of the intervillous space,
respiratory $as e#chan$e is halted %his leads to functional fetal Jbreath holdin$C
Which has a . K to *. K second limit that remains relatively constant
aldeyro K -arcia and oseiro (1.) also observed empirically that uterine
contarctions are clinically palpable only after their intensity e#ceeds 1. mm /$
>oreover, until the intensity of contarctions reaches 4. mm /$, the uterine wall can
readily be depressed by the fin$er "t $reater intensity, the uterine wall then becomes
so hard that is resist easy depression Uterine contarctions usually are not associated
with pain until their intensity e#ceeds 1; mm /$, presumably because this is the
minimum pressure re@uired for distendin$ the lower uterine se$ment and servi&s !t
follows that -ra#ton /ic&s contractions e#ceedin$ 1; mm /$ may be perceived as
uncomfortable because distension of the uterus, cervi#, and birth canal is $enerally
thou$ht to produce discomfort
/endric&s (1*) observed that Bthe clinican ma&es $reat demands upon the
uterusC %he uterus is e#pected to remain well rela#ed durin$ pre$nancy, to contract
effectively but intermittently durin$ labor, and then to remain in a state of almost
constant contaction for severa hours postpartum 8i$ure 24 K 00 demonstates an
e#ample of normal uterine activity durin$ labor Uterine activity pro$ressively and
$radually increases from prelabor throu$h late labor !nterestin$ly, as shown in 8i$ure
24 K 00, uterine contraction after birth are identical to those resultin$ in delivery of
the infant !t is there identical to those resultin$ in delivery of the infant !t is therefore
not suprisin$ that the uterus that performs poorly before delivery is also prone to
atony and puerperal hemorrha$e
ORIGIN AND PROPAGATION OF CONTACTIONS
%he uterus has not been studied e#tensively in term of its nonhormonal
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physiolo$ical mechanisms of function %he normal contractile wave of labor
ori$inates near the uterine and of one of the fallopian tubes %hus, these areas act as
Bpacema&ersC (8i$20904) %he ri$ht pacema&er usually predominates over the left
and starts most contractile waves ontractions spreds from the pacema&er area
throu$htout the uterus at 2 cmFsec, depolari7in$ the whole or$an within 1; seconds
%his depolari7in$ wave propa$ates downward toward the cervi& !ntensity is $reatest
in the fundus, and it diminishes in the lower uterus %his phenomenon is thou$ht to
reflect reductions in myometrial thic&ness from to the cervi# resumably, this
descendin$ $radient of pressure serves to direct fetal descent toward the cervi# and to
efface the cervi# !mportantly, all parts of the uterus are synchroni7ed and reach their
pea& pressure almost simultaneously, $ivin$ rise to the curvilinear waveform shown
in 8i$ure 24904 Houn$ and Phan$ (2..4) have shown that the initiation of each
contarctions is tri$$ered by a tissue9level bioelectric event
%he pacema&er theory also serves to e#plain the varyin$ intensity of ad?acent
coupled contarctions shown in panels " and - of 8i$ure 24900 uch couplin$ was
termed incoordination by aldeyro K -arcia and oseiro (1.) " contractile wave
be$ins in one corneal K re$ion pacema&er, but does not synchronously depolari7e the
entire uterus "s a result, another contraction be$ins in the contralateral pacema&er
and produces the second contractile wave of the couplet %hese small contactions
alternatin$ with lar$er ones appear to be typical of early labor !ndeed, labor may
pro$ress with such uterine activity, albeit at a slower pace %hese authors also
observed that labor would pro$ress slowly if re$ular contractions were hypotonic K
that is, contarctions with intensity less than 2; mm /$ or fre@uenly less than 2 per 1.
minutes
/auth and cowor&ers (1*) @uantified uterine contraction pressures in 1.
women at term who received o#ytocin for labor induction or au$mentation >ost of
these women achieved 2.. to effect delivery %he authors su$$ested that these levels
of uterine activity should be sou$ht before consideration of cesarean delivelry for
presumed dystocia
NE" TER!INOLOG FOR UTERINE CONTRACTIONS
%his has been recommended by the "merican olle$e of Obstetricians and
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5ynecolo$ists (2.10b), for the description and @uantification of uterine contarctions
'ormal uterine activity is defined as five or fewer contactions in 1. minutes, avera$e
over a 0. K minutes window Tachysystole was defined as more than five contarctions
in 1. minutes, avera$ed over 0. minutes %achysystole can be applied to spontaneous
or induced labor (hap2,p;2+) the term hyperstimulation was a abandoned
tewart and associates (2.12) prospectively studied uterine tachysystole in ;*4
women under$oin$ labor induction with misoprostol at ar&land /ospital %here was
no association of adverse infant outcomes with increasin$ number of contarctions per
1. minutes or per 0. minutes i# or more contractions in 1. minutes, however, werw
si$nificantly associated with fetal heart rate decelerations
CO!PLICALTIONS OF ELECTRONIC FETAL !ONITORING
Electrodes for fetal heart rate evaluation and catheters for uterine contraction
measurement are both associated with infre@uent but potentially serious
complications :arely, an intrauterine pressure catheter durin$ placement may lacerate
a fetal vessel in the placenta "lso with insertion, placental and possibly uterine
perforation can cause hemorrha$e, serious morbidity, and spurious recordin$s that
have resulted in inappropriate mana$ement evere cord compression has been
described from entan$lement with the pressure catheter !n?ury to the fetal scalp or
breech by a heart rate electrode is rarely severe /owever, application at some other
site K such as the eye in face presentations K can be serious
-oth the fetus and the mother may be at increased ris& of infection from internal
monitorin$ (8aro, 1.) calp wounds from the electrode may become infected, and
subse@uent cranial osteomyelitis has been reported (-roo&, 2..;6 E$$in&s, 2..46
>c5re$or, 1*) the "merican olle$e of Obstetricians and 5ynecolo$ists (2.12)
have recommended that certain maternal infections, includin$ human
immunodeficiency virus (/!3), herpes simple# virus, and hepatitis - and virus, are
relative contraindications to internal fetal monitorin$