Unstable Lie ZUAR 11

7/25/2019 Unstable Lie ZUAR 11

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Unstable Lie, Malpresentations,

and Malpositions

INDTRODUCTION

Near team and during labor, the fetus normally

assumes a longitudinal lie and present with the cephalic

pole to the maternal pelvis with the neck flexed and the

vertex in the lowermost part of the uterus. In

approximately 5% of labors, lie is not longitudinal. This

is usually associated with dangers to both mother and

fetus demands intervention. s with much of medicine,

the prior identification of the pregnancy at particular

risk of an unstable lie, malpresentation, or malpositioncan allow intervention in advance of a complication

developing and improve the outciome for the mother

and baby. This chapter will not consider issue relating

to fetal breech presentation as these are dealt with

elsewhere !see "hapter #$.

DEFENITIONS

Unstable Lie

This is a description generally used beyond &'

weeks( gestation when the fetal lie and presentationrepeatedly change, the lie varying from longitudinal, to

transverse, and obli)ue, and the presentation from

cephalic, to back, limbs, breech or a combination. *y

&' week the fetus usually adopts a +stable lie and a

presentation that will be unchanging until labor and

delivery. The fetal position, describing the relationship

of the fetal back to the maternal side may, however,

change.

Malpresentation Including Compound resentation

This refers to the fetus that does not present tothe maternal pelvis by the vertex alone. The presenting

part is defined as that part of the fetus that is lowermost

in the uterus. lternatives include face, brow, breech,

and shoulder, as well as compound presentations thatinvolve more than one fetal part, including a

combination of the haed or breech with a limb or limbs

or umbilical cord or a combination of limbs with or

without the umbilical cord.

Malposition

fetal malposition refers to when the fetal

vertex present to the maternal pelvis in a position other

than flexed in a accipitoanterior position. -alposotions

include occipitotranserve and occipitoposterior

positions and may involve some degree of asynclitism

!sideways tlit of the head.

igure #5/0 is an illustration of the various

positions that the vertex and brow or face may adopt

during labor.

ETIOLO!"

Unstable Lie

1nstable lie is much more common in parous

than nulliparous women, but may be caused by or

associated with a number of factors. ny situation that

discourages or prevent the fetal head or breech from

entering the maternal pelvis will predispose to an

abnormal and unstable fetal lie. igure #5/2 illustrates

some of the factors associated with an unstable fetal lie.

Maternal Factors

3I43 6IT7

Increasing muscle laxity in the maternal anterior

abdominal wall so that it fails to act as a brace and

encourage and maintain a longitudinal fetal lie is

probably the most fre)uent associated factor. In

addition, there is a commonly held view that the highly

parous urterus has reduced myometrial tone, thereby


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encouraging an unstable lie, this has not been proven

and is of doubtful relevance.

L#CENT# RE$I#

persistently changing fetal lie may be the only

clinical feature leading to the diagnosis of placenta

previa. In addition, a placenta situated in the fundus

may also predispose to an unstable lie.

EL$IC TUMORS

8varian cysts and low/lying fibroids can obstruct the

fetal head or breech entering the pelvis and may result

in a high head or breech and transverse or obli)ue lie.

UTERINE M#LFORM#TION

1terus cordiformis, subseptus, or septus may be

causative. -ore severe forms of uterine anomaly,

including uterus bicornis and uterus didelphys, are less

likely to lead to an unstable lie due to the restricted

uterine capacity9 a predisposition to fetal breech

presentation, however, result.

DISTENDED MATERNAL URINARY

BLADER

-aternal urinary retention with a distended bladder can

cause a changing fetal lie, usually only temporarily,

with resolution occurring with urinary voiding or

bladder catheteri:ation.

Fetal Factors

8;737


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unstable lie and is also potentially the most ha:ardous

for mother and fetus !see "hapter 0&.

8;I48337 6>4NN"7

The discovery of an abnormal lie during the last three

week of pregnancy may arouse suspicion of a multiple

pregnancy and lead to investigations hat result in the

diagnosis being reached9 nowadays such a diagnosis is

unlikely to have been missed until this stage of

pregnancybecause of the widespread use of routine

ultrasonography during the early weeks of gestation.

?hen the lie of one both fetuses repeatedly changes,

there is usually polyhydramnios.

>T; -"68=8-I

etal macrosomia produce the same effect as pelviccontracture and must also be considered in such cases.

>T; *N86-;ITI>=

=ignificant hydrocephaly, tumors of the fetal neck or

sacrum, fetal abdominal distension as occurs with

hydrops fetalis, and fetal neuromuscular dysfunction

!including extended legs may impede or discourage

engagement of a fetal pole in the maternal pelvis. In

cases of intrauterine death, the fetus is more likely to

present abnormally due to loss of tone, sometimes even

re)uiring delivery by cesarean section because vaginal

delivery is impossible.

Compound resentation

"ompound presentation are most usually associated

with polyhydramnios and high parity and are more

common during the early weeks of the third trimester.

-ultiple pregnancies especially those that are

monoamniotic, represent a particular risk. elvic

tumors, including uterine fibroids low in the uterine

body or an ovarian cyst situated in the pouch of


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determining the position and attitude of the fetal head.

s well as uterine contraction strength being important,

there is now good evidence that the tone of the pelvic

floor is also relevant. 1se the regional anesthesia for

the management of pain relief during labor has been

implicated as a mechanism for the increased rates of

malposition in late labor although this is disputed.

6egional anesthesia provides an extremely effective

method of reducing the distress of labor, distress that is

more common with a preexisting occipitoposteriorposition. The issue of cause and effect thus comes into

play. The experience reported from


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examination when the maternal pelvis is large and the

interloping limb with the head or breech does not delay

engagement of the presenting part.

"ompound presentations involving the umbilical cord

are usually classified according to Neagele, who

distinguished between +presentation before membrane

rupture and +prolapse after membrane rupture.

diagnosis of cord presentation will not usually be made

prior to the onset of labor except in those cases of anunstable lie when a vaginal examination is performed

as part of the assessment of the strategy for continued

management. lthough some have documented

reaching the diagnosis with ultrasound, this is not a

widely reported observation.

Face resentation

8lder texts report that abdominal palpation allows the

diagnosis of a fetal face presentation to be made by the

recognition of a much broader lower pole presenting to

the pelvis than usual and the palpation of a marked

depression between the fetal back and occiput !ig. #5/

&. This is more easily demonstrated if the fetus is lying

in a dorsoanterior, or mentoposterior presentation this is

less common than a mentoanterior presentation. It is

also said that the fertal heart sound are very easily

heard when listened to over the fetal chest, especially

with a mentoanterior position9 this potentially valuable

clinical sign is lost if hand/held


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rupture is high if labor in a parous woman is notprogressing and is left to continue for too long.

Malpositions

ew risk are associated with a fetal malposition prior to

labor. s already stated, there is a belief that prelabor

rupture of the membrane is more common with an

occipitoposterior position. =ince the head usually not

engaged and may not be well settled into the pelvis, the

risk of cord prolapsed is increased.

8nce in labor, progress may be slower than

with an anterior position, and maternal distress is often

increased, with discomfort felt particularly in the back.s well as a protracted first stage of labor, there is often

a delay during a second stage with the need for

augmentation of contractions with exytocin, or

assistance with manual rotation, forceps delivery with

or without rotation, or assistance with the ventouse.

?ith a current reluctance to engage in rotational

procedures, especially if fetal distress is suspected,

there is an increased risk of cesarean section.

It as recently been shown by one group that the

occipitoposterior position that persist to the time ofvaginal delivery present a significant risk of anal

sphincter damage for both nulliparae and multiparae.

M#N#!EMENT

Unstable Lie and Compound resentation

Antenatal

6G>NTI8N

8nce an unstable lie is identified, no specific action is

taken in anticipation that the lie will become

longitudinal before the membranes rupture or labor

starts9 this is likely to occur in more than CA% of cases.

-anipulation to a longitudinal lie at an antenatal

examination can sometimes be performed. >very

attempt should be made to identify any obvious

mechanical cause for the unstable lie, especially if it

likely to result in obstructed labor, thus re)uiring

elective cesarean section. The patient should be advised

of the risk associated with an unstable lie and the need

for urgent attention should labor start or the membranes

rupture. If the women lives very far from the delivery

unit, it may be necessary to admit her from about &'

weeks to await the onset of labor to ensure prompt

attention at the onset of labor.

number of physical exercises, such as the women

adopting the knee/elbow position for short periods on a

number of occasions each day, have been advocated to

promote spontaneous version, generally from a breechto chepalic presentation. =uch maneuvers possibly

improve the chances of a longitudinal lie by 5% to

0A%, but there is no established evidence base for this

proposition.

INTER$ENTION

dmission may be advised from &' to &D weeks

gestation onward. this enables daily observation of fetal

lie and presentation to be made9 provides to opportunity

for active treatment to correct the lie if necessary9

allows for immediate clinical assistant upon membrane

rupture or the onset of labor9 and facilitates urgent

management if the lie is not longitudinal, fetal distress

occur,, or the cord is presenting or prolapsed.


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In the event of continuing unstable lie, a

stabili:ing induction may be performed, either

immediately following admission or when an

appropriate gestation !usually &C/&D weeks has been

reached during the following days or weeks. ollowing

transfer to the labor suite an external cephalic version is

performed converting the fetal lie to longitudinal. 8nce

in position, regular abdominal palpations are performed

to confirm the longitudinal lie ismaintained and atitrated intravenous infusion of oxytocin is commenced

to stimulate uterine contractility. s soon contractions

are occuring at 0A minute intervals or more fre)uently,

a low amniotomy is performed, having ensured the lie

is still longitudinal and the presentation is not

compound and in particular that the cord is not

presenting. If the cord presents, an emergency cesarean

section is necessary. 8nce low amniotomy is

performed, a reasonable volume of amniotic fluid

should be released, followed by confirmation that thecord is not presenting and the presenting part is fixed in

the pelvic brim. Thereafter, once labor is established,

management continues as for an uncomplicated labor.

hindwater amniotomy using a


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succesfull, delivery should be achieved b cesarean

section9 attempts at version should only be performed

when immediate resort to section is available.

ALREADY RUPTURED MEMBRANES AT

FULL DILATATION

If the fetus is in a transverse or obli)ue lie or there is a

compound presentation, delivery should be performed

as urgently as possible, using the classical cesarean

section incision unless an attempt at external version

can be successfully made on opening the abdominal

wall and immediately before the uterine is incised.

transverse incision in the lower uterine segment is

likely to be inade)uate for fetal extraction because the

loss of amniotic fluid reduces the surgeon(s ability to

manipulate the fetus within the uterus. =truggling to

deliver the fetus through a lower segment incision can

cause serious trauma to the fetus, uterus, or both9 or the

uterine incision will need to be extended as an inverted

T or as a 1/shape incision. =uch incision extensions

may result in compromised healing and a vulnerable

area of scar integrity, which may predispose to uterine

rupture in future labors.


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Malpresentation

#ntenatal

8nce an identifiable specific causefor the

malpresentation has been diagnosed, treatment of the

precipitating condition may be incated !see relevant

chapter. or those cases without identifiable cause,

there are no recogni:ed and universally accepted

managements to adopt for correcting a fetal brow orface presentation. In view of the increased risk of cord

presentation and thus cord prolapse, the patient should

be advised of early admission when labor starts or

membrane rupture occurs.

s with an unstable lie, admission from &D

weeks( gestation shouldbe considered for this reason. If

delivery is indicated for other reasons, planned cesarean

section without recourse to labor may be a safer option

that inducing labor if there is a high presenting fetal

part. The alternative is labor induction with either localprostaglandins or intravenous oxytocin and low

amniotomy once contractions are established and the

fetal head fixed or engaged in the pelvic brim.

reparation should have been made to allow for rapid

cesarean section should cord presentation or prolapse

be diagnosed, with the patient forewarned of this

possibility.

Intrapartum

;abor management should be the same as for a vertex

presentation, assuming routine maternal and fetalobservation are satisfactory and good progress is

maintained E many brow presentations convert to a face

or vertex and the ma@ority of face presentations present

as mentoanterior. 8xytocin augmentation is acceptable

if uterine contractions are inade)uate, but caution

should always be shown since labor may become

obstructed with dire conse)uences if left unattended. If

progress in labor is slow, resort to cesarean section may

be a wiser option. igure #5/D illustrates the

management options

8nce full dilatation is reached with a

brow presentation, spontaneous delivery will

not folllow unless the fetus is very small or the

pelvis is unusually capacious. roviding the

assessment of the pelvis indicates that there is

no evidence of absolute disproportion, the

presentation can be converted with rotational

forceps to face or vertex, whichever proves to

be the easier, and then delivered. =ome have

advised the use of the ventouse in this situation

but thid re)uires the cup to be applied behindthe bregma and this is unlikely to be possible in

the ma@ority of cases. The current ma@ority

view is that unless the head is engaged in the

pelvis at the start of vaginal manipulations,

delivery by cesarean section is recommended.

?ith a face presentation, vaginal delivery

should be anticipated if the head is engaged, with the

delivery occuring spontaneously or assisted with

forceps. The head should be a mentoanterior position at

the delivery, achieved by forceps rotation if necessary

!see chapter '$. The ventouse has no place in the ...

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management of a face presentation. Thus cesarean sec

tion complete the delivery may be necessary if the

obstetrician dose not have the necessary skills to

conduct a rotational forceps procedure.


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Malposition

#ntenatal

There is probably little benefit from trying to alter an

occipitoposterior position diagnosed during the

antenatal period because the ma@ority of cases correct

themselves once labor starts. There may be some virtue

in advising the patient that her membranes may rupture

prior to the onset of contractions, that labor may be

more uncomportable and possibly more prolonged, and

that there is a greater chance of re)uiring assistance

with a vaginal delivery and need for delivery by

cesarean section, when compared with a more optimal

position. =ome women say that they find difficult labor

easier to cope with if forewarned, and they may be

more inclined to choose an epidural early in labor. 8n

the other hand, many occipitoposterior positions will

correct spontaneously to occipitoanterior during labor,

in which case anxiety will have been generated to no

purpose, and it may increase the likelihood of maternal

re)uest for delivery by elective cesarean section. =ome

have sugested the patient adopts a variety of positions

to encourage rotation of the fetus. n analysis of the

literature, concetranting on the use of the maternal

handskness position during the antenatal andintrapartum periods, concluded that this position

compared with others resulted in a short/term reversion


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to an anterior position. There was no indication that this

maneuver enhanced labor outcome, however.

Intrapartum

?hen the diagnosis of malposition is made early labor,

as much information as possible should be gathered at

this time about the fetal position, including the amountof head palpable per abdomen, the degree of deflexion

and asynclitism, the amount of molding and caput

formation, the level of the presenting part in relation to

the ischial spines, and maternal pelvis si:e and shape.

Issues relating to fetal well/being including fetal heart

rate patern and the color of the li)uor should also be

taken into account as with any labor.

8ption at thispoint are as illustrated in the algorithm

!see fig. #5/D and include

No specific action if acceptable progress is

being made.

rovide oxytocin augmentation if uterine

contractions are incoordinate, infre)uent, or of

poor )uality.

bandoning labor in favor of cesarean section.

>ncouraging the patient to lie on the same side

as the fetal back.

8nce the second stage of labor has been reached,

spontaneous delivery in the occipitoposterior

position may occur, or spontaneous rotation may

still occur with spontaneous delivery asoccipitoanterior. lternatively, delivery may be

delayed by a persistence of the occipitoposterior

position or the evolution of a deep transverse arrest.

It has been suggested that vaginal manipulation to

rotate the fetus to an occipitoanterior position

should be avoided if fetal distress is suspected at

that time, with resort instead to delivery by

cesarean section. The decision on management at

this stage should be determined by assessing which

method of delivery is most likely to result in earlier

delivery.

UNST#%LE LIE #ND COMOUND

RESENT#TIONS

fetal or uterine abnormality can be responsible

for the changing lie and compound presentation.

The risk of complications such as cord prolapse and

uterine rupture exists whwn the membranes rupture

or once contractions begin.

=ome of the risks can be reduced by antenatal

admission with action to correct the lie or deliver

by cesarean section before labor.

The most significant risk when the membranes

rupture or labor starts is umbilical cord prolapsed.This usually mandates delivery by cesarean

section , but replacement of the cord is sometimes

possible and should be considered.

>xternal or internal version at full dilatation should

be considered if the lie is transverse or obli)ue and

the membranes are intact.

If there is a compound presentation with ruptured

membranes, cesarean section is usually necessary,

and a classical incision may be needed.

MALPRESENTATION AND MALPOSITION

primary face precentation may indicate a fetalabnormality and warrants appropriate investigation.


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In general,a fetus with a persistent brow

presentation cannot be delivered vaginally, but

conversion to vertex or face at full dilatation should

be considered unless pelvic disproportion is

anticipated.

etuses with a face presentation can deliver

vaginally in a mentoanterior position.

etuses with a face occipitoposterior position at full

dilatation may deliver spontaneously

occipitoanterior or posterior, re)uire an assisted

delivery occipitoposterior, or be rotated and

delivered occipitoanterior , or may need to be

delivered by cesarean section.

deep transverse arrest can usually be delivered

vaginally by rotation and assisteddelivery.


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UNST#%LE LIE #ND COMOUND RESENT#TIONS

fetal or uterine abnormality can be responsible for the changing lie and compound presentation.

The risk of complications such as cord prolapse and uterine rupture exists whwn the membranes

rupture or once contractions begin.

=ome of the risks can be reduced by antenatal admission with action to correct the lie or deliver

by cesarean section before labor.

The most significant risk when the membranes rupture or labor starts is umbilical cord prolapsed.

This usually mandates delivery by cesarean section , but replacement of the cord is sometimes

possible and should be considered.

>xternal or internal version at full dilatation should be considered if the lie is transverse or

obli)ue and the membranes are intact.

If there is a compound presentation with ruptured membranes, cesarean section is usually

necessary, and a classical incision may be needed.

M#LRESENT#TION #ND M#LOSITION

primary face precentation may indicate a fetal abnormality and warrants appropriate

investigation.

Unstable Lie ZUAR 11

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