Complications of labor ROBAB DAVAR M.D. Obstetrician and Gynecologist, Fellowship of Infertility Shahid sadoughi university of medical sciences

 From 1970 to 2005, the cesarean delivery rate in the United States increased from 5% to 30%. The four primary indications for cesarean delivery include dystocia, elective repeat cesarean delivery, fetal distress, and abnormal fetal presentation.  Dystocia, translated, means difficult birth‌ and includes all abnormalities that may occur in women during labor.

Labor in its simplest terms is defined as cervical change effected by regular, painful uterine contractions. In the nulliparous woman in her first labor, cervical change usually is manifest by cervical effacement, or thinning, followed by cervical dilation. Conversely, in the multiparous woman, the initial stage of labor often is characterized by cervical dilation followed by effacement.

The first stage of labor is divided into the acceleration phase, phase of maximum slope, and deceleration phase. The acceleration phase occurs when the active phase of labor starts. The cervix usually is effaced and <4 cm dilated. In the phase of maximum slope, a minimum of 1 cm of dilation per hour can be anticipated.

In the second stage of labor, from complete dilation until delivery, again one can anticipate the laboring woman gaining a minimum of 1 cm of station of the fetal head in relation to the maternal pelvis per hour.

In the simplest terms, labor is the force of uterine contractions overcoming the resistance of the female reproductive tract, including the lower uterine segment, cervix, vagina, and perineum.

In nulliparous women, more uterine force is required to overcome resistance in the reproductive tract, and the uterus tends to be less effective in maintaining effective uterine contractions. In multiparous women, less uterine force is required, and the tissues of the reproductive outlet, having been stretched by the previous delivery, have less resistance. As a result, the myometrium of the multipara usually maintains effective contractile activity.

The cardinal movements of labor usually occur in the following sequence: engagement of the fetal head, descent of the fetal head, flexion of the fetal head, internal rotation (assumption of an occiput anterior [OA] position), extension (as the fetal head progresses through the birth canal and crowns at the perineum), external rotation (or restitution to the transverse position), and then shoulder rotation after the head has delivered.

Dystocia is more common in nulliparous women than in multiparous women and is more common in the first stage of labor than in the second stage of labor. Labor abnormalities occur in approximately 25% to 30% of nulliparous women and in 10% to 15% of multiparous women. Dystocia occurs in the second stage of labor in about 5% to 10% of nulliparous women and is relatively rare in multiparas (<2%).

Etiology of Dystocia Traditionally, the causes of abnormal labor have been attributed to the (uterine contractility), the passage‌ (maternal pelvimetry), and/or the passenger‌ (position and size of the fetus). In more scientific terms, these represent a primary dysfunctional labor, cephalopelvic or fetopelvic disproportion, abnormal fetal head position, and asynclitism.

Primary Dysfunctional Labor refers to inadequate uterine contractility to maintain appropriate progress in labor. an adequate uterine contraction pattern is one in which there are four to five concerted synchronous contractions every 10 minutes.

Smooth muscle cells of the uterus are not randomly distributed but are arranged in a specific fashion such that maximal force can be generated to effect vaginal delivery. In women with uterine embryologic abnormalities such as uterus didelphys and bicornuate uterus, labor is not often successful in achieving vaginal delivery, as global, concerted uterine contractions cannot occur because of the abnormal arrangement of uterine smooth muscle cells.

If the parturient has clinical signs of intrauterine infection, then labor progress often is desultory and not remedied with oxytocin augmentation, leading to a cesarean delivery rate of approximately 30% to 35% in these cases.

Clinical signs of intrauterine infection include maternal fever (>38آ°C), fetal tachycardia (baseline fetal heart rate of >160 beats per minute), elevated maternal white cell count, uterine tenderness when the uterus is relaxed, and foul-smelling vaginal discharge.

With the diagnosis of intrauterine infection, broad-spectrum antimicrobial agents should be administered and uterine activity stimulated with oxytocin if labor is not progressing adequately.

Cephalopelvic Disproportion True cephalopelvic disproportion (CPD), or fetopelvic disproportion, commonly is diagnosed on the labor and delivery suite, although some authorities believe that CPD occurs in as few as 1 in 250 pregnancies.

CPD occurs when the fetal birth weight or the fetal head is of sufficient size or orientation to preclude entry into the maternal pelvic inlet. This diagnosis often is made in retrospect after the birth weight is known and the positioning of the fetal head has been determined at the time of cesarean delivery. However, in the United States, the term cephalopelvic disproportion is used to describe almost any unsuccessful attempt at vaginal delivery.

Another important contribution to the fetopelvic relationship is the size of the fetus. Pregnancies with macrosomic fetuses (>4,000 g birth weight) have a greater risk of cesarean delivery for dystocia as a result of true CPD.

Abnormal Position of the Fetal Head include occiput posterior (OP), deep transverse arrest, and deflexion abnormalities such as face and brow presentations.

Fetal Abnormalities fetal conditions such as hydrocephalus, hydrops fetalis, and tumors of the head or sacrum can lead to mechanical obstruction of the birth canal and hence cause dystocia.

Prolonged Latent Phase In nulliparous women, the definition of a prolonged latent phase is a period of uterine activity without cervical change for more than 20 hours, and in multiparas this time period is 14 hours.

The management of a prolonged latent phase is controversial, and there are two commonly used approaches. Some obstetricians believe that should be managed aggressively with amniotomy and oxytocin. The other approach is to provide supportive measures including intravenous hydration and narcotic pain relief.

Arrest of Dilation An arrest of dilation occurs when there is no cervical change after 2 hours in the active phase of labor. In any case, prompt medical therapy with oxytocin usually corrects the underlying problem. In those rare cases where CPD is evident on evaluation of the patient, prompt cesarean delivery is indicated and oxytocin administration should be avoided.

Arrest of Descent If the patient does not gain station of 1 cm after an hour of adequate pushing efforts, an arrest of descent is diagnosed. The cause of this arrest disorder including inadequate uterine contractions, CPD, abnormal fetal position, and asynclitism. the obstetrician has several options including the use of oxytocin, operative vaginal delivery, or cesarean delivery.

Protracted Active Phase When cervical change continues with adequate uterine contractions in the active phase of labor but over a longer time period than anticipated, then a prolonged active phase is the diagnosis. In nulliparous patients, cervical change is <1.2 cm per hour, whereas in multiparous patients cervical change is occurring at <1.5 cm per hour.

Prolonged Second Stage. A prolonged second stage is diagnosed when the fetal head descends <1 cm per hour. A second stage lasting longer than 2 hours traditionally has been considered abnormal and an indication for operative vaginal delivery or cesarean delivery.

Artificial rupture of membranes has been used in the management of slow or desultory labor for decades. This intervention has been deplored by some obstetricians as needless intervention and recommended by others as a useful adjunct. Retrospective studies suggested that amniotomy could speed normal labor and stimulate abnormal labor to again meet normal milestones. Amniotomy

Recent studies do not support the routine use of amniotomy in the management of dystocia. Normal labor is accelerated modestly, particularly in multiparous women. There is a modest increase in the rate of intrauterine infection in women who underwent amniotomy early in the course of labor (e.g., <4 cm dilation). Rupture of the membranes also is associated with variable decelerations of the fetal heart rate as a result of umbilical cord constriction.

Conversely, amniotomy is an excellent method for labor induction if the cervix is favorable and the fetal head is well applied to the cervix. Amniotomy after 5 cm does accelerate labor in the multiparous woman but less so in the nullipara. Oxytocin tends to work more efficiently if the membranes have been ruptured.

Disruption of the membranes is required for internal monitoring of the fetal heart rate tracing or of uterine activity. Rupturing of the membranes will detect meconium staining of the amniotic fluid

Cervical examinations should be minimized after the membranes have been ruptured to decrease the chance of infection.

Operative Vaginal Delivery Operative vaginal delivery should be performed only if the following criteria are met: complete cervical dilation, engagement of the fetal head known position of the fetal head, and sufficient operator experience.

Cesarean Delivery If all the previously mentioned measures are not successful, then cesarean delivery likely is needed to obtain a good maternal and neonatal outcome. Delay in moving to cesarean delivery when indicated can potentially lead to adverse maternal and neonatal outcomes such as postpartum hemorrhage, uterine rupture, and birth injury.