Definitions
Presentation: is that part which is in or over the pelvic brim and in relation to the cervix. It is the part of the fetus occupying the lower uterine segment. The presenting part is the leading part of the leading portion of presentation felt at vaginal examination. Normal presentation is cephalic while normal presenting part is the vertex. Abnormal presentation occurs when the fetus presents in any other manner other than vertex such as breech, face, brow and shoulder presentations.
Lie: is the relationship between the long axis of the fetus and the long axis of the mother. Fetal lie can be longitudinal, transverse or oblique.
Position: is the relationship of a denominator in the presenting part to the maternal pelvis
Denominator: is the part of the presenting part, which denote the position. The denominators for cephalic, breech and shoulder presentations are vertex, sacrum and acromion respectively.
Attitude: refers to the position of the head with regard to the fetal spine (the degree of flexion and extension of the fetal head). The normal attitude is one of flexion.
Station: is a measure of descent of the bony presenting part of the fetus through the birth canal. The current standard of classification (-5 to +5) is based on a measure in centimeters of the distance of the leading bony edge from the ischial spine.
Engagement: refers to passage of the widest diameter of the presentation to a level below the plane of the pelvic inlet.
Breech presentation
Most common type of malpresentation.
Causes/risk factors
Maternal
- In most cases, no apparent cause is discernable.
- Incidence is increased among multiparous women when compared to nulliparous women.
- Presence of pelvic tumors preventing the engagement of the presenting part increases the chances of breech presentation.
- Abnormalities of uterine shape
- Abnormalities of placentation
- Cephalopelvic disproportion
Fetal
- Prematurity
- Anencephaly
- Hydrocephalus
- Neck tumors
- Multiple pregnancies
- Polyhydraminos/oligohydramnios
Types
- Complete
- Frank
- Incomplete
- Footling
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Diagnosis
Based on findings of a hard ballotable head in the upper segment of the uterus with the soft, round bottom in the lower uterine pole.
Diagnosis is confirmed using an ultrasound scan which may also show other abnormalities such as placenta previa, abnormal liquor volume, pelvic tumors, etc.
Management
Elective cesarean section
External cephalic version- carried out by trained providers in a setting that has ready access to a cesarean section.
Planned vaginal delivery might be possible in carefully selected women in whom unfavorable factors have been excluded and where appropriately trained personnel are on hand to conduct the delivery. It should only be offered in a facility with ready recourse to a cesarean section.
Face presentation
Occurs when the fetal head is hyperextended
Incidence is 1 in 500 labors
In early labor, minor deflexion occurs which may progress to hyperextension
Types of face presentation:
- Mentoanterior face 77% (commoner)
- Mentoposterior face
Presenting diameter is submento-bregmatic- 9.5cm
Etiology:
No cause could be found in >70%
- Anencephaly
- Multiple pregnancy
- Polyhydramnios
- Pelvic tumors
- Placenta previa
- Tumor of the fetal neck
- Commoner in multiparas
Diagnosis:
In early labor, the presenting part is high
Feel for the mouth, jaws, nose, malar and orbital ridges.
Mouth and maxillae form the corners of a triangle.
Delivery
For mentoanterior face-
- Spontaneous delivery/(augmentation)
- Lift-out forceps
- Vaginal delivery - 80%
Mentoposterior face-
- Augmentation
- Cesarean section commonly
Complications-
- Facial edema
- Bruises
- Soft tissue trauma
Brow presentation
Incidence- 1 in 1050
Many brow presentation in labor are transient
Midway in position between face and vertex presentation
Proceeding to full deflexion = face presentation
Or undergo spontaneous flexion= vertex presentation
Mentovertical diameter is 13.5cm hence it cannot engage in normal pelvis
Causes-
Similar to face presentation
- Prematurity
Diagnosis
Vaginal examination-
- High presenting part
- Bregma occupies the centre of dilating cervix, -frontal suture, anterior fontanelle, and orbital region can be identified
- Nose, mouth and chin cannot be felt as in face presentation
Management
With persistent brow (average sized fetus and normal pelvis), engagement is impossible because of the wide presenting diameter
Presenting part is high
C/S is best option
Cord presentation
Cord presentation: the umbilical cord is below the presenting part (head in the picture below but commonly a malpresentation) with the membranes intact.
Cord prolapse: the membranes have ruptured and the cord is beow the presenting part and has prolapsed into the vagina.
overall incidence of cord presentation is 0.1%-0.6%. It is much higher in breech presentation.
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- Cord presentation
- Cord prolapse
Risk factors
Factors preventing the proper fitting of the fetal presenting part predispose to cord prolapse. These include
- Abnormal lie
- Low birth weight
- Prematurity
- Second twin
- Polyhydramnios
- Low lying placenta
Other factors:
- Multiparity
- Procedures such as external cephalic version, internal podalic version, artificial rupture of membranes
- Use of large balloon catether for induction of labor.
Management of cord prolapse
Diagnosis is essentially clinical.
Electronic fetal monitoring can also be important for diagnosis when it is available. Abnormal FHR pattern following ROM may be the first indication of cord prolapse.
It is diagnosed by seeing or palpating the prolapsed cord on pelvic exam.
When diagnosed, summon a senior colleague and prepare operating theater for emergency delivery.
Management of cord presentation is usually by emergency C/S
Factors to consider-
- Is the fetus alive or dead?
- Lie/presentation
- Cervical dilatation
Live fetus –
- Attempt to prevent further cord compression by
- Elevating mother buttocks (knee chest position) or left lateral position
- Manually pushing the fetal head (presenting part) out of the pelvis
- Avoid handling the cord as this causes cord spasm.
- Fill the bladder with 500-700mls of normal saline
- Cephalic presenting fetus with cord prolapse
- Live fetus
- Cervix <8cm = c/s
- Cervix ≥ 8cm -assisted vaginal delivery
- Dead fetus –
- Expectant management (vaginal delivery)
- Destructive operation
Perinatal mortality associated with cord prolapse is high. These usually result from asphyxia caused by delay in effecting delivery.
Compound presentation
One or more limbs precede or lie alongside with the head in vertex presentation.
Usually the arms or where one or both arms or hands present with breech
Causes:
Preterm
Twins pregnancy
Polyhydramnios
SROM with high presenting part
Diagnosis:
Diagnosis is easy. The limb and presenting part is felt occupying the pelvis
Management-
Expectant management (the arm usually rise into the uterus with contraction)
- Transverse lie (shoulder presentation)
- Oblique lie
Predisposing factors / associated factors
- High parity
- Prematurity
- Polyhydramnios
- IUFD
- Placenta praevia
Diagnosis
- Transverse lie- fetal poles are in flanks
- Oblique lie- fetal poles are in iliac fossa and hypochondrial region
Management:
Persistent transverse lie or transverse lie in labor = C/S
There is a place for External cephalic version
Frequent changing of fetal lie and presentation in late pregnancy (>37weeks)
Management:
Stabilization, induction at term
- External cephalic version (ECV)
- Stabilizing the fetal head (maintain cephalic presentation)
- Induction of labor (perform amniotomy achieving uterine contraction, continue oxytocin infusion)
Occipitoposterior position (face to pubis)
Causes:
- Pelvis shape
- Deflexion of fetal head
Diagnosis:
- The abdomen is flat
- Fetal limbs are easily palpable
- On vaginal examination, the anterior fontanelle can be felt behind the symphysis
- Direction of the fetal ear
Management:
- Good uterine contraction/augmentation of labor= spontaneous version
- Forceps
- Vacuum extraction
- C/S
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