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OCCIPITO-POSTERIOR POSITIONDR. S.N. BERA & M. DASH

M.K.C.G MEDICAL COLLEGE ORISSA

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An abnormal position of the vertex rather than an abnormal presentation.In a vertex presentation when occiput is placed posteriorly over the sacro -illiac joint or directly over sacrum, it is called occipito -posterior position.

When the occiput is placed over right sacro-illiac joint , Right occipito-posterior(ROP)/3RD position of vertex.When the occiput is placed over left sacroilliac joint, Left occipito -posterior(LOP).also called 4th position of vertex. when it points towards sacrum, is called Direct occipito-posterior .

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INCIDENCEAt the onset of labour ,the incidence of O-P is about 10% & is much less in late second stage of labour. ROP is 5 times more common than LOP Presence of sigmoid colon on the left & dextro-rotation of the uterus favours ROP.

CAUSES

MATERNAL- shape of inlet- Anthropoid/android pelvis more than 50% cases because the wide occiput can be comfortably placed in wider posterior segment of pelvis.

FETAL-Marked deflection of head favours posterior position. It occurs due toHigh pelvic inclination. placenta previa pelvic tumoursPrimary brachycephalyUTERINE Abnormal uterine contraction

Diagnosis:

Inspection :-Abdomen looks flat below the umbilicus.

Palpation :-Fundal height :- corresponds with period of amenorrhoea.Fundal grip :- breech.

Inspection- infra umbilical flattening

Inspection- infra umbilical flattening12

Lateral grip :-Foetal back is felt on rt. Flank of mother in ROP & in left flank, in LOP.Fetal limbs are felt easily as knob like structure anteriorly.

Pelvic grip :-Head is not engaged. -Cephalic prominance (sinciput) is not felt so prominent as found in well flexed occipito anterior. -In direct occipito posterior the small sinciput is confused with breech.

-Auscultation : FHS is best heard in flank in direct occipito posterior / R.O.P. -but difficult in L.O.P.

Vaginal examination :- Finding depends upon degree of flexion of head.Confirmation made during 2nd stage of labour:- a. Sagittal suture:- occupies any of the oblique diameter of pelvis. b. posterior fontanelle :-felt near the sacro-iliac joint. c. anterior fontanelle :- felt near the ilio-pectineal eminence.

Sometimes the position is not recognized until there is delay in the second stage of labour.The diagnosis by vaginal examination may be difficult due to the formation of caput succedaneum over the presenting part.

In this case the fingers may be passed higher to feel the free margin of the ear which will point to the occiput.

MECHANISM OF LABOURThe head engages through right oblique diameter in ROP & left oblique diameter in LOP.The engaging transverse diameter of head is biparietal (9.5cm)Anterior-posterior diameter is either suboccipitofrontal (1ocm) or occipitofrontal (11.5cm).

IN FAVOURABLE CASES(90%)

Good uterine contraction results in good flexion of head. normal descent occur up to pelvic floor.Occiput rotates 3/8th of a circle(135degree) anteriorly to lie behind symphysis pubis. shoulders rotate about 2/8th of circle to occupy oblique diameter.Rest of the mechanism is like that of right occipitoanterior in ROP & left occipitotanterior in LOP.

In favourable case

UNFAVOURABLE CASES(10%)non rotation or malrotationCertain cases occiput fails to rotate-Deflexion of the headWeak uterine contractionFlat sacrumProminent ischial spineConvergent side wallsWeak pelvic floor musclesBig babyEarly drainage of liquor

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3 types resultsIncomplete forward rotation occiput rotates 1/8th of circle sagital suture comes to lie in bispinous diameter results in Deep transverse arrest. It occurs in mild deflexion of head.Nonrotation both sinciput & occiput reaches pelvic floor at same time & sagital suture lies in oblique diameter results in Oblique posterior arrest. It occurs inmoderate deflexion of head.

Malrotation - the sinciput touches pelvic floor first resulting in anterior rotation of sinciput 1/8th of circle putting occiput to sacral hollow called Persistent Occiput -posterior Position of vertex. It occurs in extreme deflexion. Also called occipito -sacral position.

In favourable circumstances in persistent occipitoposterior position, spontaneous delivery occurs as face to pubis. Descend of head occurs until root of nose hinges under symphysis pubis. Delivery of brow, vertex, occiput lastly face is born by extension .Restitution ,external rotation &delivery of trunk occurs normally.

COURSE OF LABOUR

Avg duration of both 1st& 2nd stage of labour is increased.FIRST STAGE-engagement is delayed persistence of deflexion of headDriving force transmitted through the fetal axis is not alignment with axis of inlet.

Early rupture of membrane occur.Abnormal uterine contractionSECOND STAGE-delayed due to long internal rotation or malrotation , with at times, arrest of head THIRD STAGE-increased incidence of postpartum hemorrhage & trauma to genital tract

MODE OF DELIVERY Long anterior rotation of occiput -spontaneous or assisted vaginal delivery occurs.(90%)Short posterior rotation-spontaneous or assisted vaginal delivery may occur as face to pubis. but there is more chance of perineal tear

Non-rotation or short anterior rotation-spontaneous vaginal delivery highly unlikely . May progress to prolonged or obstructed labour.

MANAGEMENT OF LABOUREarly diagnosisStrict vigilance with watchful expectancy hoping for descent &anterior rotation of occiputJudicious & timely interference if needed Early caeserean section

Management of the first stage of labour:The 1st stage is managed as in a normal case.Nothing can be done to correct the Malposition or to influence the rotation of the head at this stage.A partogram is done to monitor the :1.Uterine contraction (frequency, duration and strength ).2.Fetal heart.3.Dilatation of the cervix.

If progressive cervical dilatation does not occur augmentation with an oxytocin drip may be tried.If still no progress obtained in a few hours caesarian section (C/S) is performed.Also if there is fetal distress C/S is done

Management of the 2nd stage of labour:

1.In most cases (70% ) provided that the uterine contractions are strong and the woman is able to make good expulsive efforts the occiput rotates forward and normal delivery takes place.

2.In other cases (10% ) the baby may be delivered face-to-pubes with out difficulty but there is a great risk of a perineal tear.

3.In about 20% of cases there is failure of the presenting part to rotate and descend and such cases delivered by C/S or rotation can be enhanced by assistance .

Arrest In occipito-transverse or oblique positionVentouse- It is suitable in cases where the pelvis is adequete & non-rotation of the occiput due to weak contraction or lack of tone of pelvic floor .

Fate of OPPOPPEngaging diameter :- occipito-frontal 11.5cm or sub-occipitofrontal 10cm.Favorable (90%)Unfavorable (10%)3/8th rotationocciput comes under symphysis pubis (rt/lt occipito anterior)Normal vaginal deliveryMild deflexionModerate deflexionSevere deflexionOcciput rotate by 1/8th circleDeep transverse arrest Non-rotationOblique posterior arrestOcciput rotate posteriorly by 1/8th POPP/ occipito-sacral positionFace to pubis deliveryArrest

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Alternative methods-Manual rotation followed by forceps extractionForceps rotation & extractionCaesarean sectioncraniotomy

Half hand method

Full hand method

Manual rotation & forcep extractionFirst head is rotated manually till the occiput is placed behind symphysis . It is done with either by whole hand method or half hand method. Then forceps blades are applied.The pelvis should be adequate,Baby is of average sizeThere is good amount of liquor

Manual rotation and forceps delivery:Should be done under pudendal block or general anaesthesia.The head is rotated with the fingers to a direct anterior position.

The shoulder girdle of the fetus should be rotated at the same time as the head by pressure through the abdominal wall by external hand.

After rotation completed an obstetric forceps are applied to complete the delivery.

Difficulties are-Failure to grip head adequately due to lack of space.Failure to dislodge head from impacted positionInadequate anaesthesiaWrong case selectionComplications-Accidental slippage of headProlapse of cord

Forceps rotation&extractionIt is done by experts Kiellands forceps used.Advantage over manual rotationNo chance of displacement of headNo accidental cord prolapseRotation can be done above or below the level of obstruction

Caeserean section-if there is midpelvic contraction,I t is much safer than rotationCraniotomy- it is done in case of dead baby

Occipito sacral arrestBelow the spine

Station of headAbove the level of ischial spineC/SVentouse or forceps with deep episiotomy

Deep transverse arrest:Means arrest of labour when the fetal head has descended to the level of the ischial spines and the sagittal suture lies in the transverse diameter of the pelvis.The occiput lies on one side of the pelvis and the sinciput on the other side and the head is badly flexed.

It is only diagnosed during the 2nd stage of labour.

If the head is firmly fixed in the transverse position obstructed labour will occur

Management of DTADTA or oblique posterior arrestAssisted delivery Pelvis adequateInadequate pelvis-Manual rotation of occiput to anterior position followed by forceps extraction- vacuum delivery- forceps rotation

Dead babyCraniotomy C/S