dystocia (Indholdsside jumplinks)

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      <TextField Name="Abstract">Authors:
Torbjørn Moe Eggebø,Center for Fetal Medicine, Trondheim University Hospital (St Olavs Hospital), Trondheim, Norway. 
IInstitute of clinical and molecular medicine, Norwegian University of Science and Technology, Trondheim, Norway.

Hulda Hjartadottir, Department of Obstetrics and Gynecology, Landspitali University Hospital, Reykjavik, Iceland.

Sophia Brismar Wendel, Anna Sandström, Lone Krebs.</TextField>
      <HtmlField Name="PageContent"><![CDATA[<h2>Definition</h2>
<p>Labor dystocia means slow or prolonged labor and arrested labor means stop in labor progress. Other terms used equally for labor dystocia are dysfunctional labor, failure to progress, or obstructed labor. Labor dystocia can be diagnosed during the active phase of first stage of labor or in the second stage of labor including the descending (also called passive phase) and expulsive phase (also called bearing down or pushing).</p>
<h2>Occurrence</h2>
<p>Labor dystocia is the most commonly diagnosed aberration of labor and the most frequently indication for cesarean section and 15-20% of nulliparous women and 5% of parous women are affected by dystocia.</p>
<h2>Diagnosis</h2>
<p>Definition of labor dystocia should be based on objective criteria. Cervical dilation and fetal station in relation to time, is recorded graphically in the partograph, and the partograph is the most important tool in surveillance of labor progress. The partograph is used in differentiating between normal or slow progress. No general accepted upper limit of active phase duration exists, but 12 to 15 hours are suggested. WHO recommends a partograph with an alert line which follows one cm cervical dilatation / hour and an action line delayed four hours (some recommend using two or three hours delay). Dystocia is defined when the action line is crossed. An alternative partograph (Zhang) defines active labor at six centimeters for both primiparous and parous women. According to this curve absence of dilation for 4 hours may be normal in early labor but is prolonged after a dilation of 6 cm. Fetal descent can also be recorded in the partograph.</p>
<h2>Causes of dystocia</h2>
<p>Slow progress in labor may be due to abnormalities of the expulsive forces, fetalmaternal disproportions. malpresentations, or a combination of these factors. The consistence of the soft part of the birth canal (cervix) influences progress in the latent phase and first stage of labor, and the bony part is most important during the expulsive phase. A clinical examination is indicated when slow progress is diagnosed and includes assessment of cervical dilatation, fetal level and position. The clinical examination is subjective with rather low inter-observer agreement; however, training improves accuracy. Recent studies have shown that fetal position can be more precisely assessed with ultrasound, and ultrasound may be a helpful tool when dystocia is suspected. Occiput anterior position means that the occiput is directed towards the maternal abdomen as illustrated in figure? and occiput posterior position means that occiput is directed towards the maternal spine (fetal face directed upwards in figure?). Fetuses in occiput posterior positions have higher risk of labor dystocia.</p>
<h2>Insufficient forces</h2>
<p>Causes of dystocia are insufficient uterine contractions or inadequate maternal muscle effort during the second stage of labor. The maximum of the intrauterine pressure minus the baseline uterine tone between the contractions is called the active pressure or amplitude. This is the same as the strength of the contractions. An intrauterine pressure of 15 mmHg from baseline pressure is effective in producing cervical changes and is commonly experienced as painful. However, the threshold of pain varies from woman to woman and may be influenced by parity. Strength of contractions cannot be objectively assessed with external methods. Palpation is subjective and dependent on the experience of the birth provider and an external tocography can only measure the frequency of contractions and not the strength. During active labor the frequency of contractions is usually 4-5/10 minutes and duration 40-90 minutes. Longer or more frequent contractions increase the risk of fetal asphyxia. Insufficient contractions as cause of slow progress should only be supposed when other causes are excluded.</p>
<h2>Maternal-fetal- disproportions</h2>
<p>The bony pelvis has been classified into four basic types: gynecoid (55%), android (20%), anthropoid (20%) and platypoid (5%). The gynecoid pelvis is optimal for normal delivery. The android (male shaped pelvis) is triangular in shape, narrow in front and associated with dystocia due to failure of head rotation. African-Caribbean women are more at risk of having an adroid shaped pelvis. It is not possible to examine the pelvic shape neither with clinical examinations nor with ultrasound.</p>
<h3>Cardinal movements</h3>
<p>The shapes of the birth canal and the fetal head play critical roles in the outcome of labor in humans. The size of the fetal head at term is only a few centimeters smaller than the widest passage section. During descent, the presenting parts undergoes movements and rotations called the cardinal movements. The cardinal movements are flexion of the fetal neck, followed by rotation, extension and, last, rotation of the shoulders.</p>
<p>The third cardinal movement associated with an occiput posterior position is different; maximal flexion occurs first and is followed by extension of the fetal neck. The cardinal movements let the smallest diameter being presenting part and these movements are necessary for normal descent. The optimal diameter is when the occiput is the leading part. Failure of cardinal movements may cause dystocia.</p>
<p>[VIMEO=274441731]</p>
<h3>Macrosomia</h3>
<p>Macrosomia is associated with labor dystocia and macrosomia is usually defined as birth-weight over 4500 g irrespective of gestational age. Macrosomia affects 2-4% of fetuses. Diabetes mellitus or gestational diabetes are associated to higher frequencies of macrosomia. An elective cesarean section should be considered when macrosomia is suspected from ultrasound weight estimation, but the fetal size should be related to maternal height, history and eventual previous births.
</p>
<h2>Lie, presentation and position</h2>
<p>Fetal lie can be longitudinal, oblique or transverse. Fetal presentation describes the lowermost part of the fetus in the birth canal and can be breech, occiput, sinciput (forhead), brow or face and position describes rotation of the fetal head. Position is usually described like a clock with twelve hourly divisions.&nbsp; Most fetuses enter the birth canal in an occiput anterior or occiput transverse position, but around 25% of fetuses enter the birth canal in occiput posterior position, but the majority rotates spontaneously. Only 5-8% of fetuses are delivered in occiput posterior position. Occiput posterior position is associated with dystocia and even arrested labor. These women are more likely to undergo interventions like artificial rupture of membranes, augmentation with oxytocin (Syntocinon) and operative deliveries. Occiput posterior positon at delivery is also associated with higher risk of anal sphincher rupture. Regarding neonatal outcome, it has been shown that vaginal delivery in occiput posterior position is associated to a higher risk of low 5 minutes Apgar, low umbilical artery pH and admission to neonatal intensive care unit.&nbsp;&nbsp;</p>
<h2>Attitude</h2>
<p>Deflexion in the neck occurs in less than one percent of births and is usually combined with occiput posterior position. Brow presentations is incompatible with vaginal birth, but this presentation may change to face presentation and a vaginal delivery is only possible if the chin is upward.</p>
<h2>Ascynclitism</h2>
<p>Ascynclitism means that the anterior of posterior parietal bone is the leading part in the birth canal. Anterior ascynclitism is normal at early stages of labor, but may restrict head rotation and cause dystocia at lower stages. Posterior ascynclitism is rare, but incompatible with vaginal birth.&nbsp;</p>
<h2>Maternal factors associated with labor dystocia</h2>
<p>Labor dystocia is more common among nulliparous than parous women. Parous women without a previous vaginal delivery also have an increased risk of dystocia compared to other parous women. The risk of recurrence of labor dystocia in second delivery is dependent on several factors, but is overall about 10 %.&nbsp;<br />
A prolonged latent phase increases the risk of labor dystocia during active labor. Increasing gestational length and post-term pregnancy are also risk factors for labor dystocia. There is no consensus regarding the association between induction of labor and dystocia.&nbsp;</p>
<h2>Risks associated to dystocia</h2>
<p>Prolonged latency phase and prolonged first stage have increased risk of operative<br />
vaginal birth (vacuum extraction or forceps), cesarean sections, chorioamnionitt, postpartum haemorrhage and negative birth experience causing request for cesarean section in subsequent births. Dystocia is the most common indication for a primary caesarean section. Since many repeat caesareans are the result of previous caesarean for dystocia, prolonged labor leads to a great number of caesareans.&nbsp;<br />
A prolonged second stage is associated with urinary retention, third-and fourth degree lacerations, episiotomy and operative vaginal deliveries.&nbsp;<br />
Additional but rare complications that are associated with prolonged labor are uterine rupture, especially among parous women with previous caesarean section. In low-income countries, fistulas can be seen as a secondary effect of pressure necrosis after a very prolonged second stage.&nbsp;<br />
There is evidence that a prolonged second stage of labor is associated with adverse neonatal outcomes as low 5-minute Apgar score, asphyxia and admission to neonatal intensive care unit.<br />
<br />
</p>
<h2>Actions when slow progress is suspected</h2>
<p>All women in the latent phase should be offered a meal. Eating and drinking is also important in the active phase and might affect the duration of labor.<br />
The urinary bladder should be empty and change in maternal position is recommended. Activity may also be beneficial. One to one supervision increases the likelihood of an uncomplicated vaginal delivery. Amniotomy can be used for induction of labor, to prevent prolonged duration or therapeuthically when slow progress is already established. Amniotomy shortens duration of labor, but routinely amniotomy is not recommended. The combination of amniotomy and augmentation with oxytocin is more effective than the use of the factors alone. Amniotomy should be performed before oxytocin augmentation is started.</p>
<h2>Acceleration with oxytocin (syntocinon)&nbsp;</h2>
<p>The use of oxytocin acceleration is discussed. Oxytocin can be administrated for induction of labor, for augmentation in the first and second stages of labor and for prophylaxis or treatment of bleedings in the third stage of labor. It is recommended in women with ineffective contractions. A huge variation in the use of oxytocin acceleration is published, 32-60% among nulliparous women and 14-27% in parous women. Acceleration with oxytocin shortens birth outcomes, but an eventual reduction in instrumental delivery is not documented, although the drug has been used for this indication in over 40 years. Oxytocin is a drug with side effects and misuse may cause serious damage to the mother and fetus. The sensitivity of the drug is individual, and the acceleration should be individualised. Hyperstimulation might affect the placental circulation causing fetal distress, Hyperstimulation is one of the main causes of birth asphyxia. The use of oxytocin is also associated with uterine rupture, especially in women with a previous scar in uterus.</p>
<h2>Active management of labor</h2>
<p>The concept of &ldquo;active management of labor&rdquo; was first advocated in Ireland by O&rsquo;Driscoll and colleagues in the 1970ies. The purpose of this protocol for low-risk nulliparous women, was to reduce the length of labor and later on, additionally the caesarean section rates. Since then, the concept has been adopted in modified forms world-wide. A prolonged labor was defined as more than 12 hours, a maximum duration of 10 hours for the first stage and 2 hours for the second stage.</p>
<p>The original concept included:</p>
<ul>
    <li>One-to-one support in labor (continual support by nurse/midwife during labor)</li>
    <li>Routinely amniotomy early</li>
    <li>Use of oxytocin, early if slow progress</li>
    <li>Strict criteria for the diagnosis of labor</li>
    <li>Strict criteria for identifying progress in labor (using the partogram)</li>
    <li>Strict criteria for identifying slow progress and fetal compromise</li>
    <li>Peer review of assited deliveries</li>
</ul>
<p>Compared to routine care, active management decrease the risk of prolonged first stage of labor while the second stage is not significantly influenced. Continuous support alone, compared to routine care, significantly reduce the duration of labor and the risk of having a caesarean section.&nbsp;</p>
<h2>Shoulder dystocia&nbsp;</h2>
Shoulder dystocia is an obstructed labor whereby the anterior shoulder of the infant cannot pass below the pubic symphysis and significant manipulation is needed to deliver the fetus. It is an obstetric emergency, and fetal demise can occur due to compression of the umbilical cord. Shoulder dystocia occurs in around 0.5-1% of vaginal births and the frequency increases with increasing fetal weight; five to seven percent of infants weighing 4000 to 4500 g, 14% for those 4500 to 4750 g. and more than 20% percent of those weighing 4750 to 5000 g. Despite the additional risks related to increasing fetal weight, over 50% of casesof shoulder dystocia occur in the normal birth weight fetus and are usually unanticipated.
<h3>Antenatal risk factors</h3>
<ul>
    <li>Prior delivery with should dystocia</li>
    <li>Diabetes mellitus or gestational diabetes</li>
    <li>Macrosomia</li>
    <li>Maternal obestity</li>
    <li>Short stature&nbsp;</li>
    <li>Post-date pregnancy</li>
</ul>
<h3>Labor risk factors</h3>
<ul>
    <li>Use of oxytocin augmentation</li>
    <li>Prolonged first or second stage of labor</li>
    <li>Instrumental delivery</li>
</ul>
<h2>Procedures</h2>
<h3>Ask immediately for help (pediatrician, experienced midwife and obstetrician)</h3>
<ul>
    <li>Hyperflex the maternal hips to her abdomen</li>
    <li>Apply a suprapubid pressure (not a fundal pressure)&nbsp;</li>
    <li>Enter the vagina, push on the shoulders and try to rotate the fetus.&nbsp;</li>
    <li>Deliver the posterior arm</li>
    <li>Move the mother to an all fours position&nbsp;</li>
    <li>The last option is to push the fetal head back and do a cesarean, but this is a difficult procedure with high risk of fetal and maternal complications.</li>
</ul>
<h2>Complications</h2>
<p>The upper part of the brachial plexus may be stretched leading to dysfunction of the arm. The dysfunction may resolve spontaneously over a period of 2-3 months, but if the nerve roots are teared out of the spinal cord, the damage is permanent. Delivery of the posterior arm leads to a significant reduction in delivery force and nerve stretch.&nbsp;</p>
<h2>Asfyxia</h2>
<p>The umbilical circulation will usually be compressed in this situation and severe fetal hypoxia will occur after few minutes. The consequence may be cerebral palsy or in worst cases fetal death.</p>]]></HtmlField>
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