Foetal abnormalities Flashcards
Define lie
The relationship between the long axis of the foetus and the mother
- Longitudinal, transverse or oblique
Define presentation
The foetal part that first enters the maternal pelvis
- Cephalic vertex presentation is the most common and is considered the safest
- Other presentations include breech, shoulder, face and brow
Define position
The position of the foetal head as it exits the birth canal
- Usually the foetal head engages in the occipito-anterior position (the foetal occiput facing anteriorly) – this is ideal for birth
- Other positions include occipito-posterior and occipito-transverse
Risk factors for abnormal lie, presentation or position
Prematurity Multiple pregnancy Uterine abnormalities (e.g fibroids, partial septate uterus) Foetal abnormalities Placenta praevia Primiparity
How to identify lie
Face the patient’s head
Place your hands on either side of the uterus and gently apply pressure; one side will feel fuller and firmer – this is the back, and foetal limbs may feel ‘knobbly’ on the opposite side
How to identify presentation
Face the patient’s head
Palpate the lower uterus (above the symphysis pubis) with the fingers of both hands; the head feels hard and round (cephalic) and the bottom feels soft and triangular (breech)
You may be able to gently push the foetal head from side to side
How to identify position
During labour, vaginal examination is used to assess the position of the foetal head (in a cephalic vertex presentation)
The landmarks of the foetal head, including the anterior and posterior fontanelles, indicate the position.
Management of abnormal foetal lie
External cephalic version (ECV) - between 36-38 wks
- manipulation of foetus to cephalic presentation
- success rate of 50%
- complications foetal distress, premature rupture of membranes, APH and placental abruption
Management of malpresentation
Breech – attempt ECV before labour, vaginal breech delivery or C-section
Brow – a C-section is necessary
Face
- If the chin is anterior (mento-anterior) a normal labour is possible; however, it is likely to be prolonged and there is an increased risk of a C-section being required
- If the chin is posterior (mento-posterior) then a C-section is necessary
Shoulder – a C-section is necessary
Management of malposition
90% of malpositions spontaneously rotate to occipito-anterior as labour progresses
- If the foetal head does not rotate, rotation and operative vaginal delivery can be attempted
- Alternatively a C-section can be performed
Define breech presentation
Foetus presents buttocks or feet first
Types of breech presentation
Complete (flexed) breech – both legs are flexed at the hips and knees (foetus appears to be sitting ‘crossed-legged’)
Frank (extended) breech – both legs are flexed at the hip and extended at the knee - this is the most common type of breech presentation.
Footling breech – one or both legs extended at the hip, so that the foot is the presenting part
Risk factors for a breech presentation
Uterine - multiparity - uterine malformations - fibroids - placenta praevia Foetal - prematurity - macrosomia - polyhydramnios - twin pregnancy - abnormality
Clinical features of a breech presentation
Limited significance prior to 32-35 weeks
Identified on clinical examination - foetal heart auscultated higher
20% not diagnosed until labour -> foetal distress, meconium-stained liquor
Investigations for breech presentation
Confirmed by USS
Management of breach presentation
External Cephalic Version
C-section
Vaginal breech birth
Features of ECV
Manipulation of foetus to a cephalic presentation through maternal abdomen -> attempt vaginal delivery
40% success rate in a primiparous woman
60% success rate in a multiparous woman
Complications of ECV
Transient foetal heart abnormalities
Persistent heart rate abnormalities
Placental abruption
Need for emergency C-section
Contraindications of ECV
Recent APH
Ruptured membranes
Uterine abnormalities
Previous C-section
Features of C-section for breech presentation
If the external cephalic version is unsuccessful, contraindicated, or declined by the woman, current UK guidelines advise an elective Caesarean delivery
Evidence that perinatal morbidity and mortality is higher in cases of planned vaginal breech birth (compared to Caesarean) in term babies -there is no significant difference in maternal outcomes between the two groups
Features of vaginal breech birth
Hand off the breech - putting traction on the baby during delivery can cause the foetal head to extend, getting it trapped during delivery
Foetal sacrum does need to be maintained anteriorly, which can be done by holding the foetal pelvis
Occasionally the baby does not deliver spontaneously, and some specific manoeuvres are required:
- Flexing the foetal knees to enable delivery of the legs
- Using Lovsett’s manoeuvre to rotate the body and deliver the shoulders
- Using the Mauriceau-Smellie-Veit (MSV) manoeuvre to deliver the head by flexion
Contraindications for vaginal breech birth
Footling breech - feet and legs can slip through non-fully dilated cervix -> head and shoulders become trapped
Complications of breech presentation
Cord prolapse Foetal head entrapment Premature rupture of membranes Birth asphyxia Intracranial haemorrhage
Define oligohydramnios
Low level of amniotic fluid during pregnancy
- below 5th centile for GA
Pathophysiology of oligohydramnios
Volume of amniotic fluid increases steadily until 33 weeks of gestation - plateaus from 33-38 weeks, and then declines – with the volume of amniotic fluid at term approximately 500ml
Predominantly comprised of the foetal urine output, with small contributions from the placenta and some foetal secretions
Causes of oligohydramnios
Preterm prelabour rupture of membranes
Placental insufficiency – resulting in the blood flow being redistributed to the foetal brain rather than the abdomen and kidneys -> poor urine output.
Renal agenesis (known as Potter’s syndrome)
Non-functioning foetal kidneys, e.g. bilateral multicystic dysplastic kidneys
Obstructive uropathy
Genetic/chromosomal anomalies
Viral infections (although may also cause polyhydramnios)
Diagnosis of oligohydramnios
Made by USS
- amniotic fluid index (AFI) - measuring maximum cord-fee vertical pocket of fluid in four quadrants of the uterus and adding together
- maximum pool depth (MPD) - vertical measurement in any area
Clinical assessment of oligohydramnios
History
- Inquire about symptoms of leaking fluid and feeling damp all the time (often described as new urinary incontinence).
Examination
- Measure the symphysis fundal height.
- Perform a speculum examination (can a ‘pool’ of liquor be seen in the vagina?).
Ultrasound
- Assess for liquor volume, structural abnormalities, renal agenesis and obstructive uropathy.
- Measure foetal size. Small babies can result from placental insufficiency, which also causes oligohydramnios. There may also be a rise in pulsatility index of the umbilical artery Doppler in placental insufficiency.
Karyotyping (if appropriate) – particularly in cases of early and unexplained oligohydramnios.
Management of oligohydramnios due to ruptured membranes
Labour is likely to commence within 24-48 hours in most pregnancies
In cases of preterm rupture of membranes (i.e. before 37 weeks’ gestation), and where labour doesn’t start automatically, induction of labour should be considered around 34-36 weeks
- steroids given to aid foetal lung development
Management of oligohydramnios due to placental insufficiency
timing of delivery depends on a number of factors:
- Rate of foetal growth
- Umbilical artery and middle cerebral artery
- Doppler scans
- Cardiotocography
These babies are likely to be delivered before 36-37 weeks
Prognosis of oligohydramnios
Second trimester carriers poor prognosis
- premature rupture of membranes -> premature delivery -> pulmonary hypoplasia
Placental insufficiency
- higher rate of preterm deliveries - usually due to planned IOL
Severe muscle contractures due to lack of movement -> disability despite physio after birth
Define polyhydramnios
Abnormally large level of amniotic fluid during pregnancy
- above 95th centile
Aetiology of polyhydramnios
Idiopathic in 50-60% of cases
Any condition that prevents the foetus from swallowing – e.g. oesophageal atresia, CNS abnormalities, muscular dystrophies, congenital diaphragmatic hernia obstructing the oesophagus
Duodenal atresia – ‘double bubble’ sign on ultrasound scan
Anaemia – alloimmune disorders, viral infections
Foetal hydrops
Twin-to-twin transfusion syndrome
Increased lung secretions – cystic adenomatoid malformation of lung
Genetic or chromosomal abnormalities
Maternal diabetes – especially if poorly controlled
Maternal ingestion of lithium – leads to foetal diabetes insipidus
Macrosomia – larger babies produce more urine
Clinical assessment of polyhydramnios
Examination
- Palpate the uterus – does it feel tense?
Ultrasound
- Repeat measurement of liquor volume
- Assess foetal size
- Assess foetal anatomy to detect any structural causes
- Doppler – to detect foetal anaemia
Maternal glucose tolerance test – for maternal diabetes
Karyotyping (if appropriate) – especially if other structural abnormalities are detected, or if the foetus is small
Management of polyhydramnios
No medical intervention required in majority of women
If maternal symptoms bad -> aminoreduction
- associated with infection and placental abruption
Indomethacin can be used to enhance water retention -> reduce foetal output
n cases of idiopathic polyhydramnios, the baby must be examined before its first feed by a paediatrician. A nasogastric tube should be passed to ensure there is not a tracheoesophageal fistula or oesophageal atresia
Prognosis of polyhydramnios
Severe and persistently unexplained polyhydramnios is associated with increased perinatal mortality
- likely presence of an underlying abnormality or congenital malformation
- increased incidence of preterm labour (due to over-distension of the uterus)
Malpresentation is also more likely – as the foetus has more room to move within the uterine cavity
Care must be taken at rupture of membranes, as there is a higher risk of cord prolapse.
Higher incidence of postpartum haemorrhage, as the uterus has to contract further to achieve haemostasis
