Foetal abnormalities

Question 1

Define lie

Answer 1

The relationship between the long axis of the foetus and the mother
- Longitudinal, transverse or oblique

Question 2

Define presentation

Answer 2

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

Question 3

Define position

Answer 3

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

Question 4

Risk factors for abnormal lie, presentation or position

Answer 4

Prematurity
Multiple pregnancy
Uterine abnormalities (e.g fibroids, partial septate uterus)
Foetal abnormalities
Placenta praevia
Primiparity

Question 5

How to identify lie

Answer 5

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

Question 6

How to identify presentation

Answer 6

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

Question 7

How to identify position

Answer 7

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.

Question 8

Management of abnormal foetal lie

Answer 8

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

Question 9

Management of malpresentation

Answer 9

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

Question 10

Management of malposition

Answer 10

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

Question 11

Define breech presentation

Answer 11

Foetus presents buttocks or feet first

Question 12

Types of breech presentation

Answer 12

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

Question 13

Risk factors for a breech presentation

Answer 13

Uterine
- multiparity
- uterine malformations
- fibroids
- placenta praevia
Foetal
- prematurity
- macrosomia
- polyhydramnios
- twin pregnancy
- abnormality

Question 14

Clinical features of a breech presentation

Answer 14

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

Question 15

Investigations for breech presentation

Answer 15

Confirmed by USS

Question 16

Management of breach presentation

Answer 16

External Cephalic Version
C-section
Vaginal breech birth

Question 17

Features of ECV

Answer 17

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

Question 18

Complications of ECV

Answer 18

Transient foetal heart abnormalities
Persistent heart rate abnormalities
Placental abruption
Need for emergency C-section

Question 19

Contraindications of ECV

Answer 19

Recent APH
Ruptured membranes
Uterine abnormalities
Previous C-section

Question 20

Features of C-section for breech presentation

Answer 20

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

Question 21

Features of vaginal breech birth

Answer 21

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

Question 22

Contraindications for vaginal breech birth

Answer 22

Footling breech - feet and legs can slip through non-fully dilated cervix -> head and shoulders become trapped

Question 23

Complications of breech presentation

Answer 23

Cord prolapse
Foetal head entrapment
Premature rupture of membranes
Birth asphyxia
Intracranial haemorrhage

Question 24

Define oligohydramnios

Answer 24

Low level of amniotic fluid during pregnancy

- below 5th centile for GA

Question 25

Pathophysiology of oligohydramnios

Answer 25

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

Question 26

Causes of oligohydramnios

Answer 26

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)

Question 27

Diagnosis of oligohydramnios

Answer 27

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

Question 28

Clinical assessment of oligohydramnios

Answer 28

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.

Question 29

Management of oligohydramnios due to ruptured membranes

Answer 29

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

Question 30

Management of oligohydramnios due to placental insufficiency

Answer 30

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

Question 31

Prognosis of oligohydramnios

Answer 31

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

Question 32

Define polyhydramnios

Answer 32

Abnormally large level of amniotic fluid during pregnancy

- above 95th centile

Question 33

Aetiology of polyhydramnios

Answer 33

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

Question 34

Clinical assessment of polyhydramnios

Answer 34

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

Question 35

Management of polyhydramnios

Answer 35

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

Question 36

Prognosis of polyhydramnios

Answer 36

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