OBS - Fetal Abnormalities

Question 1

Abnormal Fetal Lie, Malpresentation and Malposition

Terminologies
Risk Factors
Investigations

Answer 1

1. ) Terminologies
   - Lie: longitudinal (normal), transverse or oblique
   - presentation: cephalic vertex (normal), others include breech, shoulder, face and brow
   - position: of the fetal head as it exits the birth canal, can be occipito-anterior (fetal occiput faces anteriorly), occipito-posterior and occipito-transverse
2. ) Risk Factors
   - prematurity, multiple pregnancy, primiparity
   - placenta praevia, fetal abnormalities
   - uterine abnormalities: fibroids, partial septate uterus
3. ) Investigations
   - any suspicion should be confirmed by ultrasound which can also show any uterine or fetal abnormalities
   - position is assessed during labour by a digital VE

Question 2

Management of Abnormal Fetal Lie, Malpresentation and Malposition

External Cephalic Version (ECV)
Management of Malpresentation
Management of Malposition

Answer 2

1. ) ECV - management of an abnormal fetal lie
   - attempted ideally between 36-38wks
   - 40/60% success in primip/multiparous women
   - 8% of breech presentations will spontaneously revert to cephalic in primiparous women > 36 wks gestation
   - anti-D prophylaxis given to Rh-ve mothers
   - complications: rare but include fetal distress, PROM, APH, placental abruption, ↑risk of a C-section
   - contraindications: recent APH, ruptured membranes, uterine abnormalities or a previous C-section
2. ) Management of Malpresentation
   - breech: attempt ECV, vaginal delivery or C-section
   - brow: C-section is necessary
   - shoulder: C-section is necessary
   - face w/ a posterior chin: C-section is necessary
   - face w/ an anterior chin: normal labour is possible but there’s a ↑risk of prolonged labour and a C-section
3. ) Management of Malposition
   - 90% of malpositions spontaneously rotate to occipito-anterior as labour progresses but if it does not rotate:
   - rotation and a forceps delivery can be attempted
   - alternatively, a C-section can also be performed

Question 3

Breech Presentation

Types of Breech Presentation
Risk Factors
Clinical Features
Differential Diagnosis

Answer 3

1. ) Types of Breech Presentation
   - frank (extended) breech: both hips are flexed and the knees are extended, this is the most common type
   - complete (flexed) breech: both hips and knees are flexed, (fetus appears to be sitting ‘crossed-legged’)
   - footling breech: one or both legs are extended at the hip so that the foot is the presenting part
2. ) Risk Factors
   - fetal: prematurity, macrosomia, polyhydramnios, multiple pregnancy, abnormality (e.g. anencephaly)
   - uterine: multiparity, fibroids, placenta praevia, uterine malformations (e.g. septate uterus)
3. ) Clinical Features - breech presentation is only relevant >35weeks as it’s likely to become cephalic
   - usually identified on examination but also suspected if the fetal heart is auscultated higher on the abdomen
   - in 20% of cases, it is not diagnosed until labour:
   - presents with: fetal distress (e.g. meconium-stained liquor), sacrum/foot through the cervical opening
4. ) Differential Diagnosis
   - oblique lie and transverse lie (shoulder presents)
   - unstable lie: presentation changes from day-to-day, this is more likely in polyhydramnios or multips

Question 4

Management of Breech Presentation

Investigations
Elective Caesarean Section
Vaginal Breech Birth
Complications

Answer 4

1. ) Investigations
   - confirmed by an ultrasound scan which can also identify the type of breech (flexed/extended/footling)
   - can also reveal any fetal or uterine abnormalities that may predispose to breech presentation
2. ) Elective Caesarean Section - preferred
   - if ECV is unsuccessful, contraindicated, or declined
   - perinatal morbidity and mortality are higher in cases of planned vaginal breech birth in term babies
   - also preferred for preterm babies due to the increased head to abdo:circumference ratio in preterm babies
3. ) Vaginal Breech Birth - if chosen or presents in advanced labour where it is the only option
   - contraindicated in a footling breech as the feet and legs can slip through a non-fully dilated cervix, and the shoulders or head can then become trapped
   - baby usually delivers spontaneously, fetal sacrum is maintained anteriorly by holding the fetal pelvis
   - do not put any traction on the baby during delivery as this can cause the fetal head to extend and get trapped
   - if it’s not delivered spontaneously, use manoeuvres:
   - flex fetal knees to enable delivery of the legs
   - Lovset’s manoeuvre to deliver the shoulders
   - Mauriceau-Smellie-Veit (MSV) manoeuvre to deliver the head by flexion, if failed, forceps can be used
4. ) Complications
   - umbilical cord prolapse, fetal head entrapment
   - PROM, birth asphyxia (due to delay in delivery)
   - ICH: rapid compression of the head during delivery

Question 5

Oligohydramnios

Pathophysiology/Definition
Aetiology
Clinical Assessment
Management/Prognosis

Answer 5

1. ) Pathophysiology/Definition - an amniotic fluid index that is below the 5th centile for the gestational age
   - normally, the fetus breathes and swallows the amniotic fluid which gets processed, fills the bladder and is voided, and the cycle repeats
   - the volume of amniotic fluid at term approx 500ml
   - anything that reduces the production of urine, blocks output from the fetus, or a rupture of the membranes can cause oligohydramnios
2. ) Aetiology
   - rupture of membranes is the most common cause
   - poor urine output: placental insufficiency (blood flow goes to the brain rather than kidneys)
   - blocked urine output: renal agenesis (Potter’s syn…), non-functioning fetal kidneys, obstructive uropathy
   - others: viral infection, genetic anomalies
3. ) Clinical Assessment
   - hx: sx of leaking fluid and feeling damp all the time
   - exam: measure SFH, a speculum (PROM)
   - USS: used to make the diagnosis by measuring the amniotic fluid index (AFI) or max… pool depth (MPD)
   - USS also assess structural abnormalities, fetal size, liquor volume, pulsatility index of the umbilical artery
   - karyotyping: in early or unexplained oligohydramnios
4. ) Management/Prognosis - depends on the cause
   - PROM: oligohydramnios in T2 carries a poor prognosis as it is usually due to PROM
   - placental insufficiency: ↑rate of preterm deliveries
   - amniotic fluid also allows the fetus to move its limbs so without this, the fetus can develop severe muscle contractures –> disability despite physio after birth

Question 6

Polyhydramnios

Definition
Aetiology
Clinical Assessment
Management

Answer 6

1.) Definition - AFI > 95th centile for gestational age

2. ) Aetiology - idiopathic in 50-60% of cases
   - conditions that prevent the fetus from swallowing: oesophageal atresia, CNS abnormalities, muscular dystrophies, congenital diaphragmatic hernia
   - duodenal atresia: ‘double bubble’ sign on a USS
   - anaemia: viral infections, alloimmune disorders
   - fetal hydrops due to parvovirus 19 infection
   - twin-twin transfusion syndrome
   - ↑lung secretions: cystic adenomatoid malformation
   - genetic or chromosomal abnormalities
   - maternal diabetes and macrosomia
   - maternal lithium ingestion –> fetal diabetes insipidus

3.) Clinical Assessment
USS: measure AFI, fetal size, liquor volume, anaemia (doppler), detect any structural causes
- maternal OGTT and test red cell antibodies (28wks)
- karyotyping: small fetus or structural abnormalities
- TORCH (viral infection) screen: Toxoplasmosis, Other (Parvovirus), Rubella, Cytomegalovirus, Hepatitis

4. ) Management - none for the majority of women
   - amnioreduction if severe maternal sx (e.g. SOB) but ↑the risk of infection and abruption so not done routinely
   - indomethacin: used to enhance water retention, and thus reduces fetal urine output, only used >32wks as it is associated with premature closure of ductus arteriosus
   - if idiopathic, the baby must be examined before its first feed, NG passed to exclude oesophageal atresia
   - complications: pre-term labour, malpresentation, umbilical cord prolapse, PPH