‫المرحلة الرابعة‬
‫جامعة بابل‬⁄ ‫كلية الطب‬
‫نسرين مالك‬-‫د‬
Obstetrics
Malposition :-This refers to the relationship between the denominator and the pelvis that makes
the spontaneous delivery unfavourable .Examples include occipito-posterior in vertex presentation;
sacro-posterior with a breech presentat; mento-posterior with face presentation.
Malposition of the fetal head (malposition of vertex presentation) :In vertex presentation, the normal position is the occipito-anterior(OA)-(right, Left or direct
occipito-anterior) in about 90 persent ,more often left occipito-anterior (LOA) rather than right, and then
undergoes a short rotation to be direct occipito-anterior in the mid-cavity. Malpositions are abnormal
positions of the vertex of the fetal head relative to the maternal pelvis,malpositions are occipito-posterior
positions.
Occipito-posterior position of the fetal head:It is a vertex presentation with fetal back directed posteriorly , mean the head inters the pelvis in one
of the oblique diameters , the occiput lies in the posterior half of the pelvis ,and directed posteriorly.
Incidence at onset of labour is 10٪
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Right occipito-posterior (ROP) is 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.
Right occipito-posterior position ROP (the occiput directed to the right sacro-iliac joint).
left occipito-posterior position LOP (the occiput directed to the left sacro-iliac joint).
The causes of occipito-posterior position:1-Android pelvis
2-Anterior placenta
3-Idiopathic .
Diagnosis:During pregnancy:1-It can be a cause of non-engagement of the fetal head before the onset of labor (in primigravida).
2-There is flattening of the lower abdomen .
3-The limbs are easily felt anteriorly .
4-Difficulty in defining the back which felt far in the flank .
5-Difficulty to hear the fetal heart sound which is heard in one of the flanks .
During labor:-In addition to the previous findings vaginal examination reveals:A-First stage of labor:1-Early rupture of membranes is common.
2-High presenting part.
3-The position can be determined from the direction of the anterior fontanelle, which can be
easily felt behind the pubis .
4-The head is poorly applied to the cervix.
The degree of flexion of the head can be determined from the fontanelles also:■-If only the anterior fontanelle can be felt the head is poorly flexed .
■-If both the anterior and posterior fontanelles can be felt the head is less poorly flexed .
■-If only the posterior fontanelle felt the head is well flexed. .
A well flexed head is more likely to rotate anteriorly.
B-Second stage of labor:Sometimes the position is not recognized until there is delay in the second stage of labor.
In the other hand the diagnosis by vaginal examination may be difficult due to the formation of
caput succedaneum over the presenting part , and some time sever moulding..In this case the fingers may
be passed higher to feel the free margin of the ear which will point to the occiput.
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Mechanism of Labour:In OPP a certain degree of deflexion is present due to opposition of the two convexities of the fetal
and maternal spines prevents flexion and promotes deflexion.As a result of deflexion, the occipito-frontal
diameter 11.5 cm enters the pelvis leading to delayed engagement.
Taking in consideration the rule that the part of the fetus that meets the pelvic floor first will rotate
anteriorly, the degree of deflexion determines the mechanism of labour as following:-
1-Normal mechanism (90%):-If the head is well flexed, the occiput will be at a lower level than
the sinciput. It will hit the pelvic floor first,undergoing long anterior rotation through 3/8 of a circle to lie
behind the symphysis pubis.The rest of the mechanism is the same as the occipito-anterior position.
2-Abnormal mechanism (10%):-This is include :■ Deep transverse arrest (1%):In mild deflexion, the occiput rotates 1/8 circle anteriorly and the head is arrested in the transverse
diameter.
Deep transverse arrest
■ Persistent occipito-posterior(right or left OPP) (3%):In moderate deflexion, the occiput and sinciput meet the pelvic floor simultaneously, no internal
rotation and the head persists in the oblique diameter.
■ Direct occipito-posterior (face to pubis) (6%):In marked deflexion, the sinciput meets the pelvic floor first, rotates 1/8 circle anteriorly and occiput
rotate backward by 1/8 of the circle to lie in the hallow of the sacrum.
In deep transverse arrest and persistent occipito-posterior(right or left OPP), no further progress
occurs and labour is obstructed, as the head cannot be delivered spontaneously.
In direct occipito-posterior, the head can be delivered by flexion supposing that the uterine
contractions are strong and there is no contracted pelvis.The head may now be born with the face towards
the posterior surface of the symphysis pubis (face to pubis).The root of the nose is pressed against the
bone.The vertex is born by flexion and followed by the occiput,then the head extends, so the face and chin
emerging from under the pubic arch. The vulval orifice is stretched by the occipito-frontal(11.5 cm)
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instead of the sub-occipito-frontal(10-10.5 cm) diameter with a difference in size of 1.5 cm and a severe
perineal tear may result.
Mechanism of direct occipito-posterior position delivery
The course of labor in occipito-posterior position(right or left OPP):Prolongation of the 1st and 2nd stages of labor is common.
Ineffective uterine contraction is common because the poorly flexed head fails to press down upon
the cervix.
In the case of persistant occipito-posterior position(right or left), assisted rotation will be required
Management of the first stage of labor:1-Exclude contracted pelvis.
2-Exclude presentation or prolapse of the cord.
3-Inertia and prolonged labour are expected .Contractions are sustained, irregular and accompanied
by marked backache which needs analgesia as pethidine or epidural analgesia, oxytocin may be
indicated unless there is contraindication.
4-Avoid premature rupture of membranes by rest in bed, no straining, avoid high enema, minimize
vaginal examinations.
5-The other management and observations as in normal labour. 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( in
case of inefficient uterine contractions). If still no progress obtained after 4-6 hours, caesarian section
(C/S) is performed. Also if there is fetal distress C/S is done.
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Management of the 2nd stage of labor:-During this period
1-Observe the mother and fetus carefully.
2-Combat inertia by oxytocin unless it is contraindicated like disproportion ,uterine scar( e.g.
previous C.S, hysterotomy, myomectomy, metroplasty or previous perforation),grand multipara
,Fetal distress.
3-Give the optimal time of second stage unless there is fetal distress( 2 hours for primigravida, and 1
hour for multipara,and extra 1 hour for both if the patient has epidural anesthesia).
4- Episiotomy is done to avoid perineal laceration.
During this stage one of the following will occur:1-Long internal rotation 3/8 circle occurs in about 90% of cases and delivery is completed as in
normal labour.
2-Direct occipito-posterior (face to pubis),occurs in about 6% of cases,the head can be delivered
spontaneously or by aid of outlet forceps.
3-Deep transverse arrest (1%) and persistent occipito-posterior (3%).
Persistent right or left occipito-posterior:The labour is obstructed and one of the following should be done:Vacuum extraction (ventouse):Proper application as near as possible to the occiput will promote flexion of the head.
Traction will guide the head into the pelvis till it meets the pelvic floor where it will rotate.
Manual rotation and extraction by forceps:The head should be engaged for manual or forceps rotation to be done. This should be done under
pudendal block or general anesthesia. The following steps are done:1-Disimpaction: the head is grasped bitemporally and pushed slightly upwards.
2-Flexion of the head.
3-Rotation of the occiput anteriorly by the right hand vaginally aided by rotation of the anterior
shoulder abdominally towards the middle line by the left hand or an assistant.
4-Fix the head abdominally by an assistant, apply forceps and extract it.
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Kielland’s forceps:- Rotation and extraction by a forceps.
Single application for rotation and extraction of the head, as this forceps has a minimal pelvic curve.
Caesarean section:-It is indicated in :- 1-Failure of the above methods.
2-Other indications for C.S. as contracted pelvis, placenta praevia, prolapsed pulsating cord before
full cervical dilatation, and elderly primigravida.
Usually the methods used in modern obstetrics are vacuum extraction and Caesarean section.
Nowadays C/S is done in these conditions to reduce fetal and maternal complications
Craniotomy:- if the fetus is dead.
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.
If the head is firmly fixed in the transverse position obstructed labor will occur.
It is commonly caused by an android pelvis which has the following feature:1-Anterior surface of the sacrum is straight .
2-The ischial spines are prominent .
3-The side walls are convergent .
So the head will fail to descend to the pelvic floor, where rotation normally occurs.
The diagnosis usually made by vaginal examination during the 2nd stage where the head found to be
arrested at the level of the ischial spine with the sagittal suture in the transverse diameter. both fontanelles
are usually palpable.
Management:-When the head is arrested in the transverse position the safest way to deliver the fetus
is by performing C/S.
Complications of malpositions:1-Premature rupture of membranes or its rupture early in labour.
2-Cord presentation and prolapse.
3-Prolonged labour due to uterine inertia.
4-Obstructed labour with higher incidence of rupture uterus.
5-Increased incidence of instrumental and operative delivery.
6-Increased incidence of trauma to the genital tract.
7-Increased incidence of postpartum haemorrhage and puerperal infection.
8-Increased incidence of perinatal morbidity and mortality.
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