OCCIPITOPOSTERIOR

DEFINITION:

It is a malposition in which the presenting part is the vertex , and the denominator which is the occiput is directed posteriorly.

INCIDENCE: 20% [R.O.P 18% & L.O.P 2%. why?]

DENOMINATOR & POSITIONS:...............

AETIOLOGY:.........................

DIAGNOSIS: *During Pregnancy

*During labor

MECHANISM OF LABOR:

1.Occurence of long anterior rotation (90%):

-Descent-->engagment-->increased flexion{occiput meets PF}

-Internal rotation 3/8 of a circle--->DOP

-Delivery as O.A(extention-->restitution-->external rotation...)

2.Failure of long anterior rotation (10%):

As the head is deflexed the mechanism of labor depends on the degree of deflexion:

a)Mild deflexion(1%):

-Descent-->Occiput meets the PF, rotates 1/8 of a circle-->Sinciput meets the PF = arrest of rotation = Deep transverse arrest[D.T.A]-->no mechnism.

b)Moderate deflexion(3%):

-Descent-->Occiput & Sinciput meet the pelvic floor-->no internal rotation = Persistent occipitoposterior[P.O.P]-->no mechanism.

c)Marked deflexion(6%):

-Descent-->Sinciput meets the PF-->rotates 1/8 of a circle anteriorly

-->Direct occipitoposterior[D.O.P]:

--->50% no mechnism.

--->50% deliver as face to pubis.(nose fixed below S.P -->occiput delivered by flexion & the face delivered by extension).

Summary:

MECHANISM OF LABOR

.Descent

2.Engagement Engaging diameter occipitofrontal (why?)

Occurence of long anterior rotation (90%)

Failure of long anterior rotation (10%):

.Increased flexion

Mild deflexion

Moderate deflexion

Marked deflexion

occiput rotates 3/8 of a circle anteriorly

Occiput rotates 1/8 of a circle

Occiput & Sinciput meet the P.F together

Sinciput rotates 1/8 of a circle anteriorly

D.O.A

D.T.A

P.O.P

D.O.P

continue delivery as normal

No mechanism

Face to pubis delivery

Causes of failure of long anterior rotation:

1.Passage: Contracted pelvis - Soft tissue obstruction - Lax PF.

2.Passenger: Deflexed head - Large head - Drained liquor.

3.Powers: Inefficient uterine contractions.

Causes of deflxion of the head in O.P :

1.The Biparietal diameter(9.5cm)engages in the sacrocotyloid diameter(9.5cm),while the small bitemporal(8.5cm) diameter descends in the wide oblique diameter(12.5cm)-->arrest of occiput & descent of the forehead.

2.Apposition of fetal & maternal spines.

3.PROM(commoly occurs)-->straightening of fetal spines.

N.B There is delayed engagment in cases of deflexion as the A.P diameter becomes the occipito-frontal(11.5cm).

Causes of vulval & perineal tears in face to pubis delivery:

1.Diameter distending the vulva is the occipitofrontal.

2.Bulky occiput distends the perineum

MANAGMENT:

I.During pregnancy:

1.Postural ttt.

2.Exclusion of CFMF , & CPD.

II.During Labor:

1.During the first stage:............

2.During the second stage:

-Wait for the long anterior rotation to occur:2hrs in PG,1hr in MG:

1.Long anterior rotation occured-->allow Sp.V.D

2.D.O.P: 50% will deliver spontaneously,

50% need forceps or CS

3.P.O.P or D.T.A:

-->Head not engaged = C.S

-->Head is engaged:

-Manual rotation + Forceps extraction or :

-Forceps rotation +Forceps extraction or:

-Ventouse rotation +Ventouse extraction

-->Dead fetus--->craniotomy

-Technique of Manual rotation:

Anesthesia , catheterzation , sterilization , towelling -->

1.Disimpaction(why?) 2.Increased flexion(why?) 3.Rotation of the head to D.O.A position. 4.Push the anterior shoulder to opposite side by the abdominal hand to untwist the neck.

Extraction by forceps is then done.

Technique of forceps rotation & extraction:

-Double application of curved forceps [Sconzoni method]

-Single application of killand forceps.

Indications of C.S : [in addition to other obstetric indications]

1-Cervical dilatation exceeds the action line in the first stage.

2-Head not engaged in the 2nd stage .

3-Head engaged but rotational technique failed.

Complications of O.P position:...................