Abnormal lie and malpresentations Flashcards
What is meant by the term ‘malpresentation’?
any non-vertex presentation - may be face, brow, breech, other part of body if lie is oblique or transverse
What proportion of fetuses are in cephalic presentation at term?
over 95% of fetuses
What are 3 examples of malpresentation?
- face
- brow
- breech
How do cephalic malpresentations differ between one another?
presenting diameter is dependent on degree of flexion or extension of the fetal head
What are 2 types of presentations which have a wide diameter to the pelvic inlet?
- Deflexed occipito-posterior
- Brow presentation
What is the structure of the fetal skull at birth and how does this change in labour?
made up of individual bony plates (occipital, sphenoid, temporal and ethmoid bones), joined by cartilaginous sutures (frontal, sagittal, lambdoid and coronal sutures)
has potential to be moulded in labour, allowing head to fit birth canal more closely
What must moulding of the skull in delivery be distinguished from and what is it?
Caput succedaneum - oedema of the presenting part of the scalp
When do scalp moulding and caput succedaneum occur?
can occur in any cephalic presentation, but more likely to occur in malpresentation
When should moulding and caput succedaneum be recorded and why?
presence or absence of both should be documented during each vaginal examination in labour; excessive moulding and caput are suggestive of an obstructed labour due to cephalopelvic disproportion (CPD)
What is face presentation?
occurs when fetal head extends right back (hyperextended so that occiput touches the fetal back)
What are 5 conditions that are associated with face presentation?
- Prematurity
- Tumours of fetal neck
- Loops of cord around the fetal neck
- Fetal macrosomia
- Anencephaly
When is face presentation typically recognised?
usually only recognised after onset of labour
What can face presentation be confused with?
if face swollen can be confused with breech presentation
What are 2 ways that a face presentation may develop during labour?
- Head enters pelvic brim with chin in transverse position (mentotransverse)
- Most (90%) rotate to mentoanterior position so head is born with flexion and deliver without problems
- Those that rotate to mentoposterior will obstruct - extending head presents increasinly wider diameter to pelvis, leading to worsening relative CPD (cephalopelvic disproportion) and impacted obstruction
What can develop as a result of face presentation?
oedema and bruising of face
What management is required for a facial presentation which progresses in the mentoposterior position?
caesarean section usually required
What is the presenting diameter in a brow presentation?
menovertical, measuring 14cm
What will be palpable on vaginal examination in brow presentation?
supraorbital ridges and bridge of nose
What are 3 ways that a brow presentation may develop during labour?
- Head may flex to vertex presentation
- May extend to face presentation
- Brow presentation may persist
What management may be required for a brow presentation?
if it persists (doesn’t change to vertex or face), caesarean section will be required
What proportion of fetal lie at term is 1. cephalic 2. breech 3. transverse or oblique?
- 95%
- 4%
- 1%
What is the definition of breech?
fetus presenting bottom first
What is the incidence of breech presentation at 1. 20 weeks, 2. 32 weeks 3. term?
- 40%
- 25%
- 3-4%
What is the chance of a breech presentation turning spontaneously after 38 weeks?
<4%
What are 6 things that breech presentation is associated with?
- Multiple pregnancy
- Bicornuate uterus
- Fibroids
- Placenta praevia
- Polyhyramnios
- Oligohydramnios
- Rarely - fetal anomaly, particularly NTDs, neuromuscular disorders and autosomal trisomies
What are 3 types of fetal anomalies that, rarely, breech presentation can be associated with?
- Neural tube defects
- Neuromuscular disorders
- Autosomal trisomies
What are 3 types of breech presentation?
- Frank breech (extended breech)
- Flexed breech (knees flexed - complete)
- Footling breech (foot down - incomplete)
At term, what proportion of breech babies are frank (extended)?
65%
What are the options for management of a breech baby?
- External cephalic version
- Caesarean section
- Vaginal delivery
What are 6 risks of vaginal delivery of a breech baby?
- Intracranial injury
- Widespread bruising
- Damage to internal organs
- Spinal cord transection
- Umbilical cord prolalse
- Hypoxia following obstruction of the after-coming head
What are the risks of caesarean section for a breech baby?
largely maternal, related to surgical morbidity and mortality
How do the risks of planned caesarean section vs vaginal delivery of a breech baby compare?
- planned c-section associated with less perinatal mortality, less serious neonatal morbidity than planned vaginal birth at term
- risk of serious maternal complications similar because vaginal delivery often ens with intrapartum c-section - greater risks than planed elective section
Who should be offered external cephalic version?
all women with a breech presentation at term unless absolute contraindication