Occipito posterior position

Abnormal labour

To define abnormal labor, a definition of normal labor must be understood and accepted. Normal labor is defined as uterine contractions that result in progressive dilation and effacement of the cervix. Any deviation from definition of normal labour is called abnormal labour. An abnormal labor may be referred to as dystocia, which simply means difficult labor or childbirth. The fetus is in an abnormal position or presentation that may result in prolonged or obstructed labour. Malpresentation and malposition may increase the duration of labor, may pose risks to maternal-fetal well-being and may necessitate operative vaginal delivery, cesarean section, or other interventions to accomplish delivery.The abnormal labour includes:

Malposition: Occipito-posterior position,Occipitotransverse position and oblique or acnclytic positions

Malpresentation:Breech presentation, transverse presentation, compound presentation, shoulder presentation, face presentation, brow presentation and Cord presentation.

Multiple pregnancy

Unstable lie

Pre-mature labour

Post-mature labour

Malposition

Fetal malposition refers to a position other than an occipitoanterior position. Or Malpositions are abnormal positions of the vertex of the fetal head (with the occiput as the reference point) relative to the maternal pelvis. Fetal malpositions are assessed during labour.

Malpresentation

Malpresentation refers to a fetal presenting part other than the vertex and includes breech, transverse, compound, shoulder, face, and brow presentation. Or malpresentations are those in which the baby's head does not present at the cervix first. Malpresentation is where the baby is in a difficult position for the birth process. It may be identified late in pregnancy or may not be discovered until the initial assessment during labour.

Signs Suggestive of Malpresentations

Pendulous abdomen.

Nonengagement of the presenting part in the last 3-4 weeks in primigravida.

Premature rupture of membranes or its rupture early in labour.

Delay in the descent of the presenting part during labour. Vaginal examination, X-ray or ultrasonography are more conclusiveCauses of Malpresentations and Malpositions

Defects in the powers:

Pendulous abdomen: laxity of the abdominal muscles.

Dextro-rotation of the uterus: rotation of the uterus in anti-clock wise favours occipito-posterior in right occipito-anterior position.

Defects in the passages:

Contracted pelvis/CPD

Android pelvis.

Pelvic tumours.

Uterine anomalies as bicornuate, septate or fibroid uterus.

Placenta praevia.

Pelvic fractures

Defects in the passenger:

Preterm foetus.

Intrauterine foetal death.

Macrosomia.

Multiple pregnancies.

Congenital anomalies as anencephaly and hydrocephalus.

Polyhydramnios.

Coils of the cord around the neck favours face presentation.

Complications of Malpresentations and Malpositions

Premature rupture of membranes or its rupture early in labour.

Cord presentation and prolapse.

Prolonged labour due to hypotonic or hypertonic inertia.

Obstructed labour with higher incidence of rupture uterus.

Increased incidence of instrumental and operative delivery.

Increased incidence of trauma to the genital tract.

Increased incidence of postpartum haemorrhage and puerperal infection.

Increased incidence of perinatal mortality.

OCCIPITO-POSTERIOR POSITION

Definition:

It is a vertex presentation with foetal back directed posteriorly.

It is abnormal fetal position with occiput at maternal sacrum. Fetal face towards maternal symphysis pubis.

In vertex presentation where the occiput is placed posteriorly over the sacroiliac joint or directly over the sacrum, it is called an occipito-posterior position. When the occiput is placed over the right sacro-illiac joint, the position is called right occipito posterior (ROP), traditionally called 3rd position of the vertex and when placed over the left sacro-illiac joint, is called left occipito-posterior (LOP), traditionally called 4rt position of the vertex and when it points towards the sacrum , is called direct occipito- posterior. Right occipito-posterior (ROP) is 5 times more common than left occipito-posterior (LOP) because:

The left oblique diameter is reduced by the presence of sigmoid colon.

The right oblique diameter is slightly longer than the left one.

Dextro-rotation of the uterus favours occipito-posterior in right occipito-anterior position.

Occipito posterior positions are the most common type malposition of the occiput and occur in approximately 10% of labours. The fetal head is usually incompletely flexed (or deflexed )and larger diameter ( the occipitofrontal ) of fetal skull present.

Aetiology:

The shape of the pelvic inlet: the shape of the inlet significantly determines the position of the head at the onset of labour. Anthropoid and android pelvises are the most common (more than 50%) cause of occipito-posterior due to narrow fore-pelvis.

Uterine factor: Abnormal uterine contraction, which may be the cause or effect, leads to persistent deflexion and occipitoposterior position.

Maternal kyphosis: The convexity of the foetal back fits with the concavity of the lumbar kyphosis.

Fetal factors: Marked deflection of the fetal head, too often favours posterior position of the vertex. The causes of deflexion are:

High pelvic inclination

Anterior insertion of the placenta: the foetus usually faces the placenta. This favours the well-flexed fetal ovoid looking towards the anterior wall of the uterus i.e. remains in dorso- posterior position. Thus, the convexities of the fetal and maternal spines are appose, leading to tendency of extension of the fetal spines with persistent deflexed attitude of the head.

Primary brachy-cepaly: This shortens the length of the lever from the frontal to atlanto-occipital joint, and there by diminishes the effective movement of flexion.Risk factors for OP position at delivery include

Nulliparity

Maternal age greater than 35 years

Obesity

African-American race

Previous OP delivery

Decreased pelvic outlet capacity

Birthweight 4000 g

Diagnosis

(On abdominal examination, the lower part of the abdomen is flattened, fetal limbs are palpable anteriourly and the fetal heart may be heard in the flank.

On vaginal examination, the posterior fontanelle is towards the sacrum and the anterior fontanelle may be easily felt if the head is deflexed.)

Landmarks of the fetal skull

Occiput transverse positions

During pregnancy

Inspection:

The abdomen looks flattened below the umbilicus due to absence of round contour of the foetal back.

A groove may be seen below the umbilicus corresponding to the neck.

Foetal movement may be detected near the middle line.

Palpation:

Fundal grip:

The breech is felt as a soft, bulky, irregular non-ballotable mass.

Umbilical grip:

The back felt with difficulty in the flank away from the middle line.

The anterior shoulder is at least 3 inches from the middle line.

The limbs are easily felt near, or on both sides, of the middle line.

First pelvic grip:

The head is usually not engaged due to deflexion.

The head is felt smaller and escapes easily from the palpating fingers as they catch the bitemporal diameter instead of the biparietal diameter in occipito-anterior.

Second pelvic grip:

The head is usually deflexed.

Auscultation:

FHS are heard in the flank away from the middle line.

In major degree of deflexion, the FHS may be heard in middle line.

Ultrasonography or lateral view x-ray.

During labour

In addition to the previous findings vaginal examination reveals:

The direction of the occiput.

The degree of deflexion.

-Elongated bag of membranes, which is likely to rupture during examination

-The sagital suture occupies any of the oblique diameters of the pelvis.

-Posterior fontanelle is felt near the sacro iliac joint. The anterior fontanelle is felt more easily because of deflexion of the head.

-In later labour, The diagnosis is often difficult because of caput formation, which obliterates the sutures and fontanelles.

Mechanism of right occipitoposterior position

The lie is longitudinal.

The attitude of the head is deflexed.

The presentation is vertex.

The position is right occipitoposterior.

The denominator is the occiput

The presenting part is the middle or anterior area of the left parietal bone.

Engagement: The head is engages through the right oblique diameter in ROP (and left oblique diameter in LOP). The engaging transverse diameter of the head is biparital (9.5) and either suboccipito- frontal(10cm) or occipito- frontal (11.5cm), lies in the right oblique diameter of the pelvic brim. The occiput points to the right sacroiliac joint and the sinciput to the left iliopectineal eminence.

Flexion and descent: Good uterine contraction result in good flexion of the head. Descent occurs until the head reaches the pelvic floor.

Internal rotation of head: The occiput reaches the pelvic floor first and rotates forwards 3/8 of a circle along the right side of the pelvis to lie under the symphysis pubis. The shoulders follow, turning 2/8 of a circle from the left to the right oblique diameter.

Crowning: The occiput escapes under the symphysis pubis and the head is crowned.

Extension: The sinciput, face and chin sweep the perineum and the head is born by a movement of extension.

Restitution: In restitution the occiput turns 1/8 of a circle to the right and the head realigns itself with the shoulders.

Internal rotation of the shoulders: The shoulders enter the pelvic in the right oblique diameter; the anterior shoulder reaches the pelvic floor first and rotates 1/8 of a circle to lie under the symphysis pubis.

External rotation of the head: At the same time the occiput turns a further 1/8 of circle to the right.

Lateral flexion: The anterior shoulder escapes under the symphysis pubis, the posterior shoulder sweeps the perineum and the body is born by a movement of lateral flexion.

Management of Labour

Spontaneous rotation to the anterior position occurs in 90% of cases. Arrested labour may occur when the head does not rotate and/or descend. Delivery may be complicated by perineal tears or extension of an episiotomy.

First stage

Exclude contracted pelvis.

Exclude presentation or prolapse of the cord.

Inertia and prolonged labour are expected so oxytocin may be indicated unless there is contraindication.

Contractions are sustained, irregular and accompanied by marked backache, which needs analgesia as pethidine or epidural analgesia, continue support must be given to mother.

Fluid should be given orally to prevent dehydration.

Carefully watch for progress of labour by abdominal and vaginal examination.

Avoid premature rupture of membranes by: -

Rest in bed,

No straining,

Avoid high enema,

Minimize vaginal examinations.

The other management and observations as in normal labour.

Second stage

Wait for 60-90 minutes.

During this period:

Observe the mother and foetus carefully.

If there are signs of obstruction but the fetal heart rate is normal allow women to walk around or change position to encourage spontaneous rotation.

If there are signs of obstruction or the fetal heart rate is abnormal (less than 100 or more than 180 beats per minute) at any stage, deliver by caesarean section.

If the membranes are intact, rupture the membranes with an amniotic hook or a Kocher clamp.

If the cervix is not fully dilated and there are no signs of obstruction, augment labour with oxytocin.

If the cervix is fully dilated but there is no descent in the expulsive phase, assess for signs of obstruction

If there are no signs of obstruction, augment labour with oxytocin.

If the cervix is fully dilated and if:

- The fetal head is more than 3/5 palpable above the symphysis pubis or the leading bony edge of the head is above -2 station, perform caesarean section;

The fetal head is between 1/5 and 3/5 above the symphysis pubis or the leading bony edge of the head is between 0 station and -2 station: Delivery by vacuum extraction and symphysiotomy;

If the operator is not proficient in symphysiotomy, perform caesarean section;

The head is not more than 1/5 above the symphysis pubis or the leading bony edge of the fetal head is at 0 station, deliver by vacuum extraction or forceps.

Third stage

PPH may occur because of prolonged labour so prophylactic intravenous ergometrine 0.2mg should be given, if there is no contraindicated for ergometrine otherwise syntocinon can be used.

Once the vaginal operative delivery is completed, meticulous inspection of the cervix and lower genital tract should be made to detect any injury.

Complication

Mother:

Prolapse cord due to ill fitness of presentinh part

Deep transverse arrest

Obstructed labour

Prolonged labour

Maternal trauma: cervix and birth canal

Retention of urine due to over stretching of urethra and bladder.

Fetus

Intrauterine hypoxia

Excessive moulding cause intracranial damage and cerebral haemorrhage

Fetal asphyxia

Neonatal trauma due to instrumentation

Increase perinetal morbidity and mortality.