O&G - Abnormal Presentation

ABNORMAL PRESENTATION (a.k.a Malpresentation)

MOHD HAFIS ZUL ARIF BIN AWANG

MBBS 2010 – IMS – MSU

Definition• Presentation = fetal part in the lower part of the

uterus over the pelvic brim, that in close proximity to the internal os of the cervix.

e.g. Cephalic (head), Breech (buttocks) & Shoulder • Presenting Part = the part of the presentation

which lies immediately inside the internal os. Determined by vaginal examination in labour Vertex, Brow or Face

• Malpresentation = any presentation other than a vertex lying in close proximity to the internal os of the cervix.

• Vertex = the area of fetal skull bounded by the two parietal eminence and the anterior and posterior fontanelles.

This is the presenting part of 95% normal term labour.

Overview

• Normal Presentation is CEPHALIC and WELL-FLEXED VERTEX

Causesa) Idiopathic (most common)b) Maternal• Multiparity• Pelvic tumors• Congenital uterine

anomalies• Contracted pelvisc) Fetal• Prematurity

• Multiple preganancy• Intrauterine death

Macrosomia• Fetal abnormality (eg:

hydrocephalus, anencephaly, cystic hygroma)

d) Placental• Placenta praevia• Polyhydromnios• Amniotic bands

Types

A. Cephalic: Face & BrowB. Breech (3-4%): Extended, Flexed & FootlingC. Transverse

D. Compound

E. Shoulder

A) Cephalic

1. Normal Presentation: Vertex • Normal Attitude: Fetus is in full flexion • Every fetal joint is flexed • Smallest fetal head diameter: Suboccipitobregmatic (9.5cm)

2) Abnormal Presentations: Extended Attitude

a) General –Abnormal Attitude: Fetal head is extended –Results in largest head diameter: Occipitomental

(11.5 cm)–Increases diameter 3 cm (24%) over flexed head –May results in Failure to Progress

b) Face Presentation c) Brow Presentation d) Shoulder Presentation

3. Abnormal Presentation: Asynclitism • Definition –Lateral flexion of head –Sagittal Suture not in midline of vaginal canal

• Interpretation –Mild asynclitism is normal –Extreme asynclitism interferes with delivery »May result in failure to progress »Interferes with forceps application

B) Breech• Definition = baby’s buttocks lie over maternal pelvis. Lie is longitudinal Head is found in the fundus• Breech delivery is the single most common abnormal

presentation. • The incidence is highly dependent on the gestational age.

More common in preterm. • Not important before 34-36 unless woman in labour.• At 20 weeks, about one in four pregnancies are breech

presentation. By full term, the incidence is about 4%.

• Types of Breech Flexed / Complete / Full breeches (15%): legs

flexed at the knees so that both buttocks and feet are presenting.

Extended / Frank breeches (70%): both legs extended with feet by head; presenting part is the buttocks.

Footling / Incomplete breeches (15%): one leg flexed and one extended. Can be ‘single’ or ‘double’ footling

• Consequences Fetal: increased risk of hypoxia, trauma in labor. Maternal: delivered by CS• Diagnosis History: breech in early pregnancy and previous

delivery, uterine fibroids and malformation Examination: longitudinal lie, head palpated at fundus,

presenting part not hard, fetal heart best heard high up on uterus.

Investigation: Confirmed with USG; should asses growth anomaly, neck hyperextension, liquor, EFW, placental site

• Management of Breech

a) External Cephalic Version (ECV) May be undertaken from 34th week gestation Containdication:i. Absolute – multiple pregnancy, APH, placenta

previa, ROM, fetal abnormality.ii. Relative – previous CS, IUGR, Rh-isoimmunization

b) Vaginal Breech Delivery• Favorable vs. Unfavorable for Vagina Delivery Previous delivery of normal-sized infant / Nulliparity,

other indication for CS EFW: 2-3.8kg / EFW >3.8kg Extended breech / Footling breech, hyperextended

neck Normal liquor / oligo- or polyhydromnios Maternal desire for vaginal delivery / CS Gestation > 33 weeks / Previous CS Grossly contracted pelvis

OR

1. Lateral flexion of trunk required to allow progress2. Deliver one leg at a time3. Deliver anterior shoulder blade and arm4. Grasped ankles and swung upwards permits

posterior arm freed.5. Body allowed to hang till head descends into

pelvis and hair line shows.6. Head my be delivered using forceps OR

7. The Mauriceau-Smellie-Viet manoeuvre: Traction by index, middle and ring finger to promote head flexion. Other hand support fetal back OR

8. The Burns-Marshall method: feet are grasped with gentle traction arc over maternal abdomen mouth freed delivery completed by further swinging over maternal abdomen.

N.B: Delivery of head as slow as possible to decrease damage to

skull membrane by sudden compression and release Air passage should be cleared as quickly as possible by

aspirating nose and mouth

c) Breech Extraction• Obstetrician places hand inside the uterus and

grasps the foot.• Baby delivered by traction of the foot• Procedure now restricted to delivery of second

twin (lying transverse and membrane ruptured)• If membrane intact, ECV possible.d) Caesarean Section

C) Transverse• Transverse lie occurs frequently in early pregnancy, when it is

of no consequence. At 16 weeks gestation, about half of all pregnancies will be transverse lie. This number steadily falls as pregnancy advances and the incidence of transverse lie by the 28th week is well below 10%. It falls steadily thereafter.

• If the fetus remains in a transverse lie, it cannot be delivered vaginally as the diameter of the fetal presenting part (the whole body, in this case) cannot descend through the birth canal.

• Complication: ruptured uterus, prolapse umbilical cord. For these reasons, women found to have a transverse lie in

labor will usually have a CESAREAN SECTION.

• Exceptions to this indication for cesarean section: If labor is occurring during the middle trimester and fetus is

not considered viable, it may be possible for this very small and fragile fetus to compress enough to squeeze through the pelvis. In this case, fetal survival would not be an issue.

It may be possible to perform an external version, In the case of twins, it would be acceptable to allow labor,

even though the second twin is in transverse lie, anticipating that after delivery of the first twin, you would reach in and perform an internal version, converting the transverse lie to cephalic or breech presentation prior to delivery.

• Management: Evaluate the patient carefully with ultrasound to

determine if there are any predisposing factors, such as a placenta previa or pelvic kidney that could modify your management of the patient.

So long as a placenta previa is not present, many obstetricians will check the patient's cervix at frequent intervals to detect early cervical dilatation and the consequential increased risk of cord prolapse.

Sometimes, these patients are delivered early by scheduled cesarean section to avoid that risk.

D) Compound• Compound presentation means that a fetal hand is

coming out with the fetal head. This is a problem because:

The amount of baby that must come through the birth canal at one time is increased.

There is increased risk of mechanical injury to the arm and shoulder, including fractures, nerve injuries and soft tissue injury.

• A compound presentation may be resolvable if the fetus can be encouraged to withdraw the hand, for example.

• If the fetus and arm are relatively small in comparison to the maternal pelvis, vaginal delivery may still be possible, but with some risk of injury to the arm.

• If the fetus and arm are relatively large in comparison to the maternal pelvis, obstructed labor will occur and a cesarean will be needed.

E) Shoulder• Shoulder presentation means that the fetal shoulder

is trying to come out first. This is a more advanced form of transverse lie and is undeliverable vaginally.

THANK YOU