Occipitoposterior Position PDF

Malposition - Occipitoposterior position Melad Alias  Objectives Definition Epidemiology Etiology Diagnosis Management Complication  Definition Occipito posterior (OP) position is a longitudinal lie, cephalic presenta...

Malposition - Occipitoposterior position Melad Alias  Objectives Definition Epidemiology Etiology Diagnosis Management Complication  Definition Occipito posterior (OP) position is a longitudinal lie, cephalic presentation with the fetal back directed posterior. lt is considered a malposition rather than a malpresentation.  Epidemiology Occiput posterior (OP) position is the most common fetal malposition, are encountered in around 40 % of cases during antenatal period and 20% at the onset of labour. Most (90%) will spontaneously rotate in anterior position before delivery. The overall rate of occiput posterior deliveries was 5.5 percent, but the proportion was nearly twice as high in nulliparas (7.2 percent) compared with multiparas (4 percent).  It is important because it is associated with labor abnormalities that may lead to adverse maternal and neonatal consequences, particularly operative vaginal or cesarean birth.  Epidemiology 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.  pelvis (85%) as android the commonest Etiology (anthropoid) due to narrow forpelvis. Other causes (15%) : Maternal kyphosis (The convexity of the fetal back fits with the concavity of the lumbar kyphosis, placenta praevia, pelvic tumors, pendulous abdomen,  Diagnosis During pregnancy Inspection: ◦ The abdomen looks flattened below the umbilicus due to absence of round contour of the fetal back. ◦ A groove may be seen below the umbilicus corresponding to the neck. ◦ Foetal movement may be detected near the middle line.  Diagnosis : Auscultation: FHS are heard in the flank away from the middle line. Ultrasonography or lateral view x-ray, confirm the diagnosis especially in obese women.  Diagnosis During labour : In addition to the previous findings vaginal examination reveals: 1. The direction of occiput. 2. The degree of deflexion.  Mechanism of labour A certain degree of deflexion is present due to: Opposition of the two convexities of the foetal and maternal spines prevents flexion and promotes deflexion. The longer biparietal diameter (9.5cm) enters the narrow sacro-cotyloid diameter (9cm) while the shorter bitemporal diameter (8cm) enters the longer oblique diameter 12cm As a result of deflexion, the occipito-frontal diameter 11.5 cm enters the pelvis leading to delayed engagement.  Mechanism of labor Taking in consideration the rule that the part of the foetus that meets the pelvic floor first will rotate anteriorly, the degree of deflexion determines the mechanism of labour as follow: Normal mechanism (90%) Deflexion is corrected and complete flexion occurs. The occiput meets the pelvic floor first, long anterior rotation 3/8 circle occurs bringing the occiput anteriorly and the fetus is delivered normally. Abnormal mechanism 10% Deep transverse arrest 1% ◦ In mild deflexion, the occiput rotates 1/8 circle anteriorly and the head is arrested in the transverse diameter. Persistent occipito-posterior 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 the occiput becomes direct posterior Sig ns Ome ns  Management of labor 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. Avoid premature rupture of membranes by:- ◦ rest in bed, ◦ no straining, ◦ avoid high enema, ◦ minimise vaginal examinations.  Management Second stage Wait for 60-90 minutes. During this period: ◦ Observe the mother and foetus carefully. ◦ Combat inertia by oxytocin unless it is contraindicated. One of the following will occur: ◦ Long internal rotation 3/8 circle: ▪ occurs in about 90% of cases and delivery is completed as in normal labour. ◦ Direct occipito-posterior (face to pubis): ▪ occurs in about 6% of cases. ▪ the head can be delivered spontaneously or by aid of outlet forceps. ▪ Episiotomy is done to avoid perineal laceration which results from ▪ the vulva is distended by the large occipito-frontal diameter 11.5 cm, ▪ the perineum is overstretched by the large occiput.  Continuation Deep transverse arrest 1% and persistent occipito-posterior 3%: ▪ The labour is obstructed and one of the following should be done: ▪ A- Vacuum extraction (ventouse). ▪ B- Manual rotation and extraction by forceps. ▪ C- Rotation and extraction by a forceps. ▪ D- cesarian section failure of above method. ▪ E- Craniotomy if the fetus is dead. Actually speaking, the methods used in modern obstetrics are vacuum extraction and Caesarean section.