Breech presentation, which complicates
3–4% of all pregnancies, occurs when the fetal pelvis or lower extremities
engage the maternal pelvic inlet. Three types of breech are distinguished,
according to fetal attitude (Fig 21–1). In frank breech, the hips
are flexed with extended knees bilaterally. In complete breech, both
hips and knees are flexed. In footling breech, 1 (single footling
breech) or both (double footling breech) legs are extended below the level of
the buttocks.
In singleton breech presentations in which the infant
weighs less than 2500 g, 40% are frank breech, 10% complete breech, and 50%
footling breech. With birth weights of more than 2500 g, 65% are frank breech
, 10% complete breech, and 25% footling breech.
Fetal position in breech presentation is determined
by using the fetal sacrum as the point of reference to the maternal pelvis.
This is true for frank, complete, and footling breeches. Eight possible
positions are recognized: sacrum anterior (SA), sacrum posterior (SP), left
sacrum transverse (LST), right sacrum transverse (RST), left sacrum anterior
(LSA), left sacrum posterior (LSP), right sacrum anterior (RSA), and right
sacrum posterior (RSP). The station of the breech presenting part is the
location of the fetal sacrum with regard to the maternal ischial spines.
Causes
Before 28 weeks, the fetus is small
enough in relation to intrauterine volume to rotate from cephalic to breech
presentation and back again with relative ease. As gestational age and fetal
weight increase, the relative decrease in intrauterine volume makes such
changes more difficult. In most cases, the fetus spontaneously assumes the
cephalic presentation to better accommodate the bulkier breech pole in the
roomier fundal portion of the uterus.
Breech presentation occurs when
spontaneous version to cephalic presentation is prevented as term approaches or
if labor and delivery occur prematurely before cephalic version has taken
place. Some causes include oligohydramnios, hydramnios, and uterine anomalies
such as bicornuate or septate uterus, pelvic tumors obstructing the birth
canal, abnormal placentation, advanced multiparity, and a contracted maternal
pelvis.
In multiple gestations, each fetus may
prevent the other from turning, with a 25% incidence of breech in the first
twin, nearly 50% for the second twin, and higher percentages with additional
fetuses. Additionally, 6% of breech presentations are found to have congenital
malformations, which include congenital hip dislocation, hydrocephalus, anencephalus,
familial dysautonomia, spina bifida, meningomyelocele, and chromosomal
trisomies 13, 18, and 21. Thus, those conditions that alter fetal muscular tone
and mobility increase the likelihood of breech presentation.
Performance of Leopold's maneuvers and
ballottement of the uterus may confirm breech presentation. The softer, more
ill-defined breech may be felt in the lower uterine segment above the pelvic
inlet. Diagnostic error is common, however, if these maneuvers alone are used
to determine presentation.
During vaginal examination, the round,
firm, smooth head in cephalic presentation can easily be distinguished from the
soft, irregular breech presentation if the presenting part is palpable.
However, if no presenting part is discernible, further studies are necessary
(ie, ultrasound).
X-ray studies will differentiate
breech from cephalic presentations and help determine the type of breech by
locating the position of the lower extremities. X-ray studies can reveal
multiple gestation and skeletal defects. Fetal attitude may be seen, but fetal
size cannot readily be determined by x-ray film. Because of the risks of
radiation exposure to the fetus with this technique, ultrasonography is now
used instead of radiography to determine fetal presentation or malformations.
Ultrasonographic scanning by an
experienced examiner will document fetal presentation, attitude, and size;
multiple gestation; location of the placenta; and amniotic fluid volume.
Ultrasound also will reveal skeletal and soft-tissue malformations of the
fetus.
Following confirmation of breech
presentation, the mother must be closely followed to evaluate for spontaneous version
to cephalic presentation. If breech presentation persists beyond 36 weeks,
external cephalic version should be considered (see below).
In women considering a vaginal breech
delivery, radiographic pelvimetry using x-ray, computed tomography, or magnetic
resonance imaging should be performed to rule out women with a borderline or
contracted pelvis. Attempts at vaginal delivery with an inadequate pelvis are
associated with a high rate of difficulty and significant trauma to mother and
fetus. Difficult vaginal delivery may still occur in women with adequate pelvic
measurements.
Patients with singleton breech
presentations are admitted to the hospital with the onset of labor or when
spontaneous rupture of membranes occurs because of the increased risk of
umbilical cord complications. Upon admission, a repeat ultrasound is obtained
to confirm the type of breech presentation and to ascertain head flexion. The
fetus is again screened for lethal congenital malformations, such as
anencephaly, which would preclude cesarean delivery for fetal indications. A
thorough history is taken, and a physical examination is performed to evaluate
the status of mother and fetus. Based on these findings, a decision must be
made regarding the route of delivery (see below).
Continuous electronic fetal heart rate
monitoring is essential during labor. If a fetal electrocardiographic electrode
is needed, care should be taken to avoid injury to the fetal anus, perineum, and
genitalia when attaching the electrode to the breech presenting part. An
intrauterine pressure catheter can be used to assess the frequency, strength,
and duration of uterine contractions. With the catheter in place, fetal
distress or dysfunctional labor can easily be identified and the decision to
proceed with a cesarean section made expeditiously to optimize fetal outcome.
The use of oxytocin in the management
of breech labor is controversial. Although some obstetricians condemn its use,
others use oxytocin with benefit and without complications. Generally, oxytocin
should be administered only if uterine contractions are insufficient to sustain
normal progress in labor. Continuous fetal and uterine monitoring should be
used whenever oxytocin is administered.
The decision regarding route of
delivery must be made carefully on an individual basis. Criteria for vaginal or
cesarean delivery are outlined in Table.
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Cesarean Delivery
The type of incision chosen is
extremely important. If the lower uterine segment is well developed, as is
usually the case in women at term in labor, a transverse "lower
segment" incision is adequate for easy delivery. In premature gestations,
in an unlabored uterus, or in many cases of malpresentation, the lower uterine
segment may be quite narrow, and a low vertical incision is almost always
required for atraumatic delivery.
Obstetricians who contemplate
performing a vaginal breech delivery should be experienced in the maneuver and
should be assisted by 3 physicians: (1) an experienced obstetrician who will
assist with delivery; (2) a pediatrician capable of providing total
resuscitation of the newborn; and (3) an anesthesiologist, to ensure that the
mother is comfortable and cooperative during labor and delivery. The type of
anesthesia required depends on the type of breech delivery. Multiparous women
undergoing spontaneous breech delivery may require no anesthesia or only
intravenous analgesia for pain relief during labor and a pudendal anesthetic
during delivery. Epidural anesthesia may also be administered during labor or
in anticipation of partial breech extraction, including application of Piper
forceps to the aftercoming head. In emergency circumstances, complete
relaxation of the perineum and uterus is essential for a successful outcome.
This is accomplished by immediate induction of inhalation anesthesia or by
administration of intravenous nitroglycerin.
During spontaneous delivery of an
infant in the frank breech position, delivery occurs without assistance, and no
obstetric maneuvers are applied to the body. The fetus negotiates the maternal
pelvis as outlined below, while the operator simply supports the body as it
delivers.
Engagement occurs when the
bitrochanteric diameter of the fetus has passed the plane of the pelvic inlet.
As the fetus descends into the pelvis (Fig 21–2), the buttocks reach the
levator ani muscles of the maternal pelvis. At this point, internal rotation
occurs, whereby the anterior hip rotates beneath the pubic symphysis, resulting
in a sacrum transverse position. The bitrochanteric diameter of the fetal
pelvis is now in an anteroposterior position within the maternal pelvis. The
breech then presents at the pelvic outlet and, upon emerging, rotates from
sacrum transverse to sacrum anterior. Crowning occurs when the bitrochanteric
diameter passes under the pubic symphysis. As this occurs, the shoulders enter
the pelvic inlet with the bisacromial diameter in the transverse position. As
descent occurs, the bisacromial diameter rotates to an oblique or
anteroposterior diameter, until the anterior shoulder rests beneath the pubic
symphysis. Delivery of the anterior shoulder occurs as it slips beneath the
pubic symphysis. Upward flexion of the body allows for easy delivery of the
posterior shoulder over the perineum.
As the shoulders descend, the head engages the pelvic
inlet in a transverse or oblique position. Rotation of the head to the occiput
anterior position occurs as it enters the midpelvis. The occiput then slips
beneath the pubic symphysis, and the remainder of the head is delivered by
flexion as the chin, mouth, nose, and forehead slip over the maternal perineum.
As delivery of the breech occurs,
increasingly larger diameters (bitrochanteric, bisacromial, biparietal) of the
body enter the pelvis, whereas in cephalic presentation, the largest diameter
(biparietal diameter) enters the pelvis first. Particularly in preterm labors,
the head is considerably larger than the body and provides a better
"dilating wedge" as it passes through the cervix and into the pelvis.
The smaller bitrochanteric and bisacromial diameters may descend into the
pelvis through a partially dilated cervix, but the larger biparietal diameter
may be trapped. Delivery in these cases is described in the following.
Partial breech extraction (assisted
breech extraction) is used when the operator discerns that spontaneous delivery
will not occur or that expeditious delivery is indicated for fetal or maternal
reasons. The body is allowed to deliver spontaneously up to the level of the
umbilicus. The operator then assists in delivery of the legs, shoulders, arms,
and head.
As the umbilicus appears at the
maternal perineum, the operator places a finger medial to 1 thigh and then the
other thigh, pressing laterally as the fetal pelvis is rotated away from that
side by an assistant. Thus, the thigh is externally rotated at the hip and
results in flexion of the knee and delivery of one, then the other, leg. The
fetal trunk is then wrapped in a towel to support the body. When both scapulae
are visible, the body is rotated counterclockwise. The operator locates the
right humerus and laterally sweeps the arm across the chest and out the
perineum (Fig 21–3). In a similar fashion, the body is rotated clockwise to
deliver the left arm. The head then spontaneously delivers by gently lifting
the body upward and applying fundal pressure to maintain flexion of the fetal
head (Fig 21–4). During partial breech extraction, the anterior shoulder may be
difficult to deliver if it is impacted behind the pubic symphysis. In this
event, the body is gently lifted upward toward the pubic symphysis, and the
operator inserts 1 hand along the hollow of the maternal pelvis and identifies
the posterior humerus of the fetus. By gentle downward traction on the humerus,
the posterior arm can be easily delivered, thus allowing for easier delivery of
the anterior shoulder and arm.
Complications of Breech Delivery
Umbilical cord compression and
prolapse may be associated with breech delivery, particularly in complete (5%)
and footling (15%) presentations. This is due to the inability of the
presenting part to fill the maternal pelvis, either because of prematurity or
poor application of the presenting part to the cervix so that the umbilical
cord is allowed to prolapse below the level of the breech (see below). Frank
breech presentation offers a contoured presenting part, which is better
accommodated to the maternal pelvis and is usually well applied to the cervix.
The incidence of cord prolapse in frank breech is only 0.5% (the same as for
cephalic presentations).
Compression of the prolapsed cord may
occur during uterine contractions, causing moderate to severe variable
decelerations in the fetal heart rate and leading to fetal anoxia or death.
Continuous electronic monitoring is mandatory during labor in these cases to
detect ominous decelerations. If they occur, immediate cesarean delivery must
be performed.
The incidence of birth trauma during
vaginal breech delivery is 6.7%, 13 times that of cephalic presentations
(0.51%). Only high forceps and internal version and extraction procedures have
higher rates of birth injury than do vaginal breech deliveries. The types of
perinatal injuries reported in breech delivery include tears in the tentorium
cerebellum, cephalohematomas, disruption of the spinal cord, brachial palsy,
fracture of long bones, and rupture of the sternocleidomastoid muscles. Vaginal
breech delivery is the main cause of injuries to the fetal adrenal glands,
liver, anus, genitalia, spine, hip joint, sciatic nerve, and musculature of the
arms, legs, and back.
Factors contributing to difficult
vaginal breech delivery include a partially dilated cervix, unilateral or
bilateral nuchal arms, and deflexion of the head. The type of procedure used
may affect the neonatal outcome.
Delivery of a breech fetus may progress
even though the cervix is only partially dilated because the bitrochanteric and
bisacromial diameters are smaller than the biparietal diameter. This is true
especially in prematurity. The hips and shoulders may negotiate the cervix, but
the aftercoming head becomes entrapped, resulting in difficult delivery and
birth injury.
During partial breech extraction and
more often in total breech extraction, excessive downward traction on the body
results in a single or double nuchal arm. This occurs because of the rapid
descent of the body, leading to extension of 1 or both arms, which become
lodged behind the neck. When delivery of the shoulder is difficult to
accomplish, a nuchal arm should be suspected. To dislodge the arm, the operator
rotates the body 180 degrees to bring the elbow toward the face. The humerus
can then be identified and delivered by gentle downward traction. In cases of
double nuchal arm, the fetus is rotated counterclockwise to dislodge and
deliver the right arm and rotated clockwise to deliver the left arm. If this
action is unsuccessful, the operator must insert a finger into the pelvis,
identify the humerus, and possibly extract the arm, resulting in fracture of
the humerus or clavicle. Nuchal arms cause a delay in delivery and increase the
incidence of birth asphyxia.
Hyperextension of the head is
defined as deflexion or extension of the head posteriorly beyond the
longitudinal axis of the fetus (5% of all breech deliveries). Causes of
hyperextension include neck cysts, spasm of the neck musculature, and uterine
anomalies, but over 75% have no known cause. Although deflexion may be
documented by ultrasonographic or x-ray studies weeks before delivery, there is
little apparent risk to the fetus until vaginal delivery is attempted. At that
time, deflexion causes impaction of the occipital portion of the head behind
the pubic symphysis, which may lead to fractures of the cervical vertebrae,
lacerations of the spinal cord, epidural and medullary hemorrhages, and
perinatal death. If head deflexion is diagnosed prior to delivery, cesarean
section should be performed to avert injury. Cesarean section cannot prevent
injuries such as minor meningeal hemorrhage or dislocation of the cervical
vertebrae, which may develop in utero secondary to longstanding head deflexion.
More complex delivery procedures have
a higher rate of birth trauma. Whereas few infants are injured during
spontaneous breech births, as many as 6% are injured during partial breech
extraction and 20% during total breech extraction. Injuries associated with
total breech extraction usually are extensive and severe, and this procedure
should never be attempted unless fetal survival is in jeopardy and cesarean
section cannot be immediately performed.
An additional important factor in
breech injury and perinatal outcome is the experience of the operator.
Inexperience may lead to hasty performance of obstetric maneuvers. Delay in
delivery may result in birth asphyxia due to umbilical cord compression, but
haste in the management of breech delivery results in application of excessive
pressure on the fetal body, causing soft-tissue damage and fracture of long
bones. Too-rapid extraction of the body from the birth canal causes the arms to
extend above the head, resulting in unilateral or bilateral nuchal arms and
difficult delivery of the aftercoming head. All breech deliveries should be
performed slowly and methodically by experienced obstetricians who execute the
maneuvers with gentleness and skill—not speed.
The incidence of cesarean section for
breech delivery has been steadily increasing, from approximately 30% in 1970 to
85% in 1999. A recent review of breech deliveries in California revealed an 88%
cesarean section rate, with more vaginal deliveries performed in public
teaching hospitals and far fewer in private facilities. A decreased number of
practitioners currently are skilled in vaginal breech delivery, and although
academic faculty support its teaching, there are insufficient numbers of
vaginal breech deliveries to properly teach this procedure at most institutions.
It should be noted that cesarean section for the immature or malformed fetus
does not improve chances for perinatal survival; vaginal delivery should be
performed in these cases.
The Term Breech Trial Collaborative
Group recently conducted a randomized controlled trial to compare planned
cesarean section with vaginal birth for selected breech presentation
pregnancies. They found that fetuses of women who underwent planned cesarean
sections were less likely to die or to experience poor outcomes in the immediate
neonatal period than were fetuses of women who underwent vaginal birth. There
was no difference in the 2 groups in terms of maternal mortality or serious
morbidity. They concluded that a policy of planned cesarean section will result
in 7 cesarean births to avoid 1 infant death or serious morbidity. Because of
the results of this trial, the American College of Obstetricians and
Gynecologists recommends planned cesarean delivery for persistent breech
presentations at term.
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