Dr S khazardoost
Associate professor of OB&GYN
Perinatalogy Department TUMS

• The most common indication for primary cesarean delivery
• Highest in nulliparous women with term pregnancies

Two phases of labor
• Latent phase —begins when the mother perceives regular contractions, which are typically mild and infrequent . it can be difficult to determine the time of onset of contractions and the time of transition to active phase.
• Active phase —painful contractions of increasing frequency, intensity, and duration accompanied by more rapid cervical change (at least 1 cm/hour).

• Assessment of the onset of latent phase difficult
• Patient has entered latent phase is primarily based upon the woman's history and the judgment of the attending provider

• Regular uterine contractions
• Gradually soften, efface, and begin to dilate the cervix
• Irregular contractile activity beginning in the midtrimester , with gradual alterations in the size, shape, and consistency of the cervix occurring over the remaining months of the pregnancy

• The definitions of a prolonged latent phase are still based on data from Friedman and modern investigators have not particularly focused on the latent phase of labor

Prolonged latent phase (eg,>20 hours in nulliparous women and >14 hours in multiparous women) should not be an indication for cesarean delivery

• 500 primigravidas
• The first stage of labor was further divided into the latent phase, acceleration phase, phase of maximum slope, and a deceleration phase
• Transition from the latent phase to the acceleration phase appeared to occur at 3 to 4 cm
• Minimum rate of acceptable cervical dilation during the active phase of labor was 1.2 cm/hour for nulliparous patients and 1.5 cm/hour for multiparous patients

• Active-phase arrest traditionally has been defined as the absence of cervical change for
2 hours in the presence of adequate uterine contractions and cervical dilation of at least 4 cm.

• Change in patient characteristics
• Anesthesia practices
• Obstetrical practices
• Friedman's database on 500 case
• In the retrospective study conducted at 19 US hospitals, the duration of labor was analyzed in 62,415 parturient women, each of whom delivered a singleton vertex fetus vaginally and had a normal perinatal outcome

Greater than 50 percent of patients do not dilate at a rate of >1 cm/hour until 5 to 6 cm dilation
Abrupt change in the rate of cervical dilation indicating a clear transition from latent phase to active phase
No deceleration phase at the end of first stage

• Cervical change between 3-6 cm
• More than 6h from 4-5cm
• More than 3h from 5-6cm
• Clinically practical to consider all women to be in active phase once reached to 6cm

• The duration of the first stage of labor was significantly longer in induced labor
• From 4-6 cm, nulliparous and multiparous women dilated at essentially the same rate , and more slowly than historically described
• Beyond 6 cm , multiparous women dilated more rapidly

• According to Friedman the mean
(95th percentile) duration of the active phase in nulliparous and parous women was 4.6 hours (11.7) and 2.4 hours (5.2) , respectively
• Zhang found that the median (95th percentile) duration of time for the cervix to dilate from 4 to 10 cm in nulliparas and multiparas was 5.3 hours (16.4) and 3.8 hours (15.7
), respectively

Cervical dilation of 6 cm should be considered the threshold for the active phase of most women in labor

• labor may take more than six hours to progress from 4 to 5 cm and more than three hours to progress from 5 to 6 cm , regardless of parity
• Labor accelerates much faster after 6 cm, and is significantly faster in multiparas compared to nulliparas at this dilation.

• Change in Definition:
Arrest of labor
Cervical dilation ≥6 cm with ruptured membranes and:
No cervical change for ≥4 hours despite adequate contractions
No cervical change for ≥6 hours with inadequate contractions

• One or more abnormalities of the cervix, uterus, maternal pelvis, or fetus (ie, power, passenger, or pelvis)
• Very long cervicx in mid-pregnancy are more likely to experience poor progress during labor and cesarean delivery
• Genetic component

• Hypocontractile uterine activity is the most common couse of protraction and arrest
• Monitored by palpation, external tocodynamometry, or internal uterine pressure catheters
• 91 percent of women in spontaneous active labor achieved contractile activity greater than 200
Montevideo units and 40 percent reached 300
Montevideo units
• Neuraxial is not associated with a significant increase in duration of the first of labor or cesarean delivery
Increases in the second stage of labor and use of oxytocin and operative vaginal delivery

• This diagnosis is often based upon observation of protracted or arrested labor during the active phase
• It is often due to fetal malposition (eg, extended or asynclitic fetal head) or malpresentation (mentum posterior, brow) rather than a true disparity between fetal size and maternal pelvic dimensions

Clinical and radiologic assessment of the maternal pelvis and fetal size are inexact with poor predictive value
abnormal progress of labor and certain physical findings protracted or arrested descent with increased molding, especially overlap of the parietal bones at the sagittal suture, is suggestive of CPD

• The final centimeter of cervix anteriorly between the pelvic brim and the fetal head
• Greater than 30 minutes may be a variation of normal or may indicate a labor abnormality or malposition, such as occiput posterior
• An abnormality or malposition is more likely if the lip becomes edematous
• Repositioning the parturient
• Manual reduction to avoid prolonged labor and the risk of cervical laceration, cervical necrosis, or detachment of the lip
• Not advise routine manual reduction of an anterior lip because of the risk of cervical injury and hemorrhage

Manual reduction of an anterior cervical lip
• Place your fingers on the anterior lip where it touches the fetal head
• During a contraction, use your fingers to push the cervical lip backwards until it slips over the fetal head and above the interior border of the symphysis pubis
• Hold the cervical lip in this position while waiting for the next contraction.
• Allow your fingers, but not the cervix, to be pushed downwards and out as the fetal head descends with contractions and maternal pushing
• Remove your fingers when the cervix reduces or if the procedure is unsuccessful or poorly tolerated

• Associated with longer duration of active labor and the second stage
• Higher risk of arrest of descent requiring operative delivery
• The length of the second stage correlate with the degree of rotation away from occiput anterior

• Rare pregnancy complication associated with obstructed labor
• It is not clear if it is the cause or the result of the associated dystocia
• May also occur between delivery of the first and second twin

Neuraxial anesthesia was not associated increase in first stage duration
Maternal obesity

First stage latent phase
• Longer in induced labor
• Difffernt from false labor
• Theraputic rest opioid analgesics
• Oxytocin
• Amniotomy

Patients with protracted active phase
• to confirm that the patient is in the active phase
• administer oxytocin , and wait four hours

If the maternal and fetal status allow, cesarean deliveries for failed induction of labor in the latent phase can be avoided by allowing longer durations of the latent phase (up to 24 hours) and requiring that oxytocin be administered for at least 12-18 hours after membrane rupture before the induction a failure

• Membrane rupture and oxytocin administration , except in rare circumstances, should be considered prerequisites to any definition of failed labor induction

First stage active phase
• Confirm the active phase( cervix is at least 6 cm)
• Traditionally two hours of adequate contraction
• Oxytocin augmentation and evaluating cervical change after 4 hours of adequate contraction and 6 hours of inadequate contraction

• Oxytocin and amniotomy
• Misoprostol
• Ambulation and continuous labor support

Good neonatal outcome after protracted first stage

• Amniotomy with or without oxytocin not shorten the first stage ,possible reduction in cs
• Volume replacement
• Avoidance of op position
• Pelvic floor muscle exercises

• labor that lasts no more than three hours from onset of contractions to delivery
• This occurs in approximately 2% of all deliveries
• Not usually associated with significant maternal or infant morbidity and mortality
• Short labors can be associated with placental abruption, uterine tachysystole and recent maternal cocaine use

precipitous second stage is the most common labor abnormality associated with shoulder dystocia , although the rates of permanent injury did not increase