Abnormal labor:
Labor becomes abnormal when there is poor progress[ as evidenced by a delay in cervical dilatation or descent of presenting part ] and or the fetus shows signs of compromise. Also if there is a fetal malpresentation, multiple gestation, a uterine scar, or if labor has been induced, labor cannot be considered normal.Poor progress in the first stage of lobar:
It is defined as cervical dilatation of less than 2 cm in 4 hours, usually associated with failure of descent and rotation of the fetal head .
Progress in labor is dependent on three variables:
1-the passages: related to bony pelvis and the soft tissues abnormalities e.g remodeling of cervix, impacted rectum, full bladder, cervical fibroid and ovarian cyst may all lead to delay in active phase.
2-the passenger:3 m role "malpresentation, malposition, macrosomia.
3-the power: i.e. uterine contraction the only component that can truly be manipulated.
Disorders of labor:
3 major disorders of labor are characterized and include:
1-Prolonged latent phase:
during the latent phase, changes occur in the ground substance glycoprotein, collagen content and hydration state of the cervix, which result in the remodeling and effacement that may be observed during this period. Friedman described the latent phase as lasting up to (20 hours) in nulliparous( median 9 hours)& (14 hours) in multiparous ( median 5 hours).
During the latent phase, women may experience painful contractions and need a lot of support. However, it is important that unnecessary interventions to accelerate labor are not implemented at this points, as clinical studies have demonstrate that oxytocin augmentation during this phase does not result in an increased in the vaginal delivery rate, but a 10 fold increase in the incidence of caesarean delivery and a 3 folds increase in low Apgar scores. The only intervention, careful explanation and the provision of adequate analgesia before the cervical changes complete & active phase of labor is entered.
2-Primary dysfunctional labor:
PDL is define as poor progress during the active phase of labor. This affects up to (25% of nulliparous) & ( 10 % of multiparous) & whereas no single a etiology is responsible for all cases, (70% of nulliparous) & ( 80% of multiparous) will respond to oxytocin. This observation suggests that poor in coordinate uterine activity is a significant factor, although an improvement in the rate of cervical dilatation does not correlate with improved outcomes in terms of vaginal delivery, PDL may culminate in an obstructed labor & is associated with higher rates of maternal infection, uterine rupture & PPH. The women should offered hydration, good pain relief and emotional support. When poor progress is suspected it is recommended repeat vaginal examination( 2 hours rather than 4 hours)if delay confirmed the women should offered ARM, if still there is poor progress in a further 2 hours so use of oxytocin infusion to augment the labor, the infusion is started at a slow rate and then increased every (30 minutes). multiparous women are less likely to experience poor progress in labor secondary to PDL, extreme caution must be taken to make a such diagnosis because there is other explanation, such as malposition and malpresentation is more likely, if progress fails to occur despite (4-6 hours of augmentation with oxytocin, C/S is recommended.
3-Secondary arrest:
As we know the active phase of labor can be subdivided to:
1-acceleration phase: between the latent phase and the maximum slope.
2-maximum slope: linear dilatation with time.
3-decceleration phase: at the end of the active phase and prior to full dilatation.
Secondary arrest define as cessation of cervical dilatation following normal period of active phase dilatation although other factors that implicated in PDL can cause it but is most likely related to relative and absolute CPD. Although augmentation with oxytocin may be consider but the diagnosis should be sought before any intervention is taken to prevent complication that associated with absolute CPD & early treatment by C/S.
Cephalo pelvic disproportion:
it is implies anatomical disproportion between the fetal head & maternal pelvis. It can be due to large head, small pelvis or a combination of the two. Women of small stature (1.60 m) with a large baby in their first pregnancy may develop this problem, the pelvis may be unusually small because of previous fracture or metabolic bone disease, rarely a fetal anomaly will contribute to CPD, obstructive hydrocephalus may cause macrocephaly& fetal thyroid & neck tumor may cause extension at the fetal neck.
Relative CPD is suspected in labor if:
a-progress is slow or actually arrest despite efficient uterine contractions.
b-the fetal head is not engaged.
c-vaginal examination shows severe molding& caput formation.
d-the head is poorly applied to the cervix.
Oxytocin can be given carefully to primigravida with mild to moderate CPD as long as CTG is reactive.
Relative disproportion may be overcome if the malposition is corrected. Oxytocin must never be used in a multiparous women where CPD is suspected.
Malpresentation:
vital to good progress in labor is the tight application of the fetal presenting part on to the cervix.
Face presentation may apply poorly to cervix leading to poor progress although vaginal delivery is still possible.
Brow presentations are associated with the mento-vertical diameter which is too large to fit through the bony pelvis unless flexion occurs or hyper extension to face presentation so the brow present as a poor progress in first stage & often in multiparous women.
Shoulder presentation cannot deliver vaginally. all mal presentation are common in multiparous & carry risk of uterine rupture.
Abnormalities of birth canal (the passages):
abnormal pelvis & abnormalities of the uterus & cervix can cause delay labor, fibroid or ovarian cyst can prevent descend of fetal head. Cervical dystocia term used to described a non-complaint cervix which efface & fail to dilate because of severe scarring for e.g due to cone biopsy & treated by C/S.
Poor progress in the second stage of lobar:
birth of baby is expected to take place within 3 hours of the start of the active second stage (pushing) in nulliparous women, & 2 hours in parous women, delay in the second stage is diagnosed if delivery is not imminent after 2 hours of pushing in nulliparous labor (1 hour for parous women).
The causes of second stage delay can again be classified as abnormalities of the powers, the passenger & the passages
secondary uterine inertia is common cause of second stage delay, & may be exacerbated by epidural analgesia. Having achieved full dilatation, the uterine contractions become weak & ineffectual & this sometimes associated with maternal dehydration & ketosis. If no mechanical problem is anticipated, the treatment is with rehydration & IV oxytocin if the women primiparous . delay can also be occur due to persistent OP position of the fetal head, in this case, the head will either have to undergo a long rotation to OA or be delivered in the OP position, i.e face to pubes. Delay in the second stage can also occur because of a narrow mid- pelvis ( android pelvis) which prevents internal rotation of the fetal head this may result in arrest of the descent of fetal head at the level of the ischial spines in the transverse position, a condition called deep transverse arrest.
Instrumental birth should be considered for prolonged second stage it safely performed in the labor room, or may be more safely carried out in the theatre with easy recourse to C/S if the attempt is failed.
Obstructed lobar:
It is a condition in which failure or no progress in spite of strong uterine contraction ie failure of cervix to dilate or failure of presenting part to descend through the pelvic canal, it is most dangerous condition if untreated & can be fatal to both mother & fetus.
Clinical feature:
It is more important for early detection of possible obstructed lobar because if lobar is allow to progress to point of obstruction, death of fetus will occur & the life of mother in danger.
If there is signs of deterioration, the general condition of the mother is important to examine she may look pale, anxious, dehydrated, exhausted & uncooperative. The women PR, temp, is increased & UOP is reduce there is ketonuria & acetonic breathing .
On pelvic examination there is hot dry vagina with edematous cervix, the presenting part is high, the membrane is ruptured early in lobar & there may be caput succedaneum.
The possibility of obstructed lobar should be suspected when there is failure to progress in the 1st stage of lobar when the cervix fail to dilate progressively.
The partogram will give an early warning sign that progress has been ceases & the descend is not continue to occur in the 2nd stage of lobar. Any failure in the progress of lobar require carful abdominal & vaginal examination to exclude any possible causes of obstruction.
In neglected cases of obstruction, uterine contraction continue lead to progressive retraction causing abnormal stretching & thinning of the lower segment become very evident & known as "retraction ring of Bandl " & can be seen or felt on abdominal examination.
excessive retraction of the uterus should never be allowed to develop, The cause of obstructed lobar should discovered during pregnancy or early in lobar & the treatment than applied.
The aim of treatment is to deliver the mother immediately by the safest method, intrauterine manipulation best avoided to prevent rupture of abnormal thin lower segment & C/S it is usually less hazardous ( antibiotics, blood transfusion has been confirm to reduce the risk of C/S in this case .
This lecture by Dr-Nadia AL-Assady
CABOG - FIBOG