occipito-posterior position

Question 1

What are the causes of occipito-posterior position?

Answer 1

Passages
- abnormal shaped pelvis
- contracted/fractured pelvis
- lumbar kyphosis
- uterine anomaly
- uterine fibroid
- placenta Previa
- rupture uterus

Passenger
- prematurity
- macrosomia
- multiple gestation
- oligohydramnios/polyhydramnios
- coils of cord around the neck
- IUFD

Power
- uterine inertia
- pendulous abdomen
- uterine hypertonicity

Question 2

What are the complications of occipito-posterior position on the mother?

Answer 2

1- prolonged or obstructed labour
2- PROM -> infection
3- injury to bladder, vagina & rectum
4- maternal hemorrhage
5- thrombo-embolism
6- uterine intertia
7- ruptured uterus

Question 3

What are the complications of occipito-posterior position on the fetus?

Answer 3

1- mortality & morbidity
2- cord prolapse
3- birth asphyxia
4- meconium aspiration
5- perinatal infection
6- traumatic injury
7- intra-cranial hemorrhage
8- congenital anomalies

Question 4

Why is ROP more common than LOP?

Answer 4

Dextro-rotation of the uterus favors ROP
- head enters the pelvis in the right oblique diameter (12.5cm)

Question 5

What are the different mechanisms of labour in OP position?

Answer 5

DIRECT OP (face to pubis)
- marked deflexion -> sinciput reaches pelvic floor first -> head is delivered in flexion

PERSISTENT OBLIQUE OP
- moderate deflexion -> occiput & sinciput reach the pelvic at the same time -> no internal rotation -> obstructed labour

DEEP TRANSVERSE ARREST
- mild deflexion -> occiput reaches first -> occipito-transverse -> obstructed labour

Question 6

What is the reason for perineal tears in direct OP?

Answer 6

• the vulva is overdistended by the occipito-frontal diameter (11.5cm)
• perineum is distended by bulky occiput

Question 7

What are the factors that favor long anterior rotation?

Answer 7

• primigravida
• strong uterine contractions
• adequate pelvis
• good pelvic floor
• intact membranes

Question 8

What are factors that interfere with long anterior rotation?

Answer 8

• multigravida
• uterine inertia
• contracted pelvis
• lax or rigid pelvic floor
• rupture of membranes
• epidural anesthesia

Question 9

How is OP position diagnosed during pregnancy?

Answer 9

INSPECTION
- flat abdomen below umbilicus
- sub-umbilical transverse groove
- fetal movements near middle line

PALPATION
- umbilical grip: back is away from middle line & limbs are near
- 1st pelvic grips: head is smaller + not engaged
- 2nd pelvic grips: head is deflexed

AUSCULTATION
- FHS are heard away from midline below level of umbilicus

ULTRASOUND
- to confirm

Question 10

What should be examined in vaginal examination of OP position?

Answer 10

• cephalic presentation, lambda is posterior, degree of deflexion, presence of moulding
• degree of cervical dilatation
• rupture of membranes & cord prolapse
• exclude contracted pelvis

Question 11

How is OP position managed?

Answer 11

Exclude contracted pelvis & cephalo-pelvic disproportion to allow vaginal delivery

1ST STAGE OF LABOUR
- abnormal progress & PROM

2ND STAGE
1- watchful expectancy for 1-2 hours hoping for long anterior rotation
2- If Direct OP -> spontaneous delivery or aid with forceps & generous episiotomy

Question 12

What are the indications of C-section in OP?

Answer 12

1- persistent oblique OP
2- deep transverse arrest
3- contracted pelvis
4- other OB indications