Foetal abnormalities Flashcards
What is a breech position? What are the 3 different types?
When the baby comes out buttocks or feet first rather than head first.
Complete: both legs flexed at hips and knee (cross legged), bum first
Frank (extended) breech: both legs flexed at hip but extended at knee (commonest)
Footling: one or both legs extended at hip so foot is presenting part
How common is breech presentation?
20% of babies are breech at 28 weeks gestation. most revert to a cephalic presentation (head down) spontaneously and only 3% are breech at term
What may cause breech presentation?
usually due to chance but 15% have RF:
- multiparity
- uterine malformation
- fibroids
- placenta praevia
- prematurity
- macrosomia
- polyhydramnios
What are the clinical features of a breech presentation?
- usually identified on clinical exam- round fetal head can be felt in upper uterus and irregular mass in the pelvis, the fetal heartbeat can be auscultated higher on maternal abdomen
- however this isnt usually important until 32-35 weeks
- 20% of breech presenation is not diagnosed until labour, this can present with fetal distress- eg meconium stained liquor, on vaginal examination the sacrum or foot may be felt though the cervical opening
how should a suspected breech presentation be investigated?
- confirm with uss, also tells you the type of breech and predisposing fetal abnormalities
What are the 3 management options for breech presentation?
- external cephalic version
- c section
- vaginal breech birth
What is external cephalic version and when is it used?
- manipulation of fetus to cephalic presentation through the abdomen
- if successful (40%) means they can have vaginal delivery
- attempted in all unless recent antepartum haemorrhage, ruptured membranes, uterine abnormalities or previous c section
- may get transient fetal heart abnormalities but these revert to normal
- rarer complications inc placental abruption and more persistent heart rate abnormalities
When is c section used for breech births?
- if external cephalic version is unsuccessful, contraindicated or declined, guidelines are they get a c section
- perinatal morbidity and mortality is higher in planned breech vaginal births compared w/ c section
When may a vaginal breech delivery be used and not used?
- cannot be used if footling breech as feet can slip through non- fully dilated cervix and shoulders/ head can be trapped
- pt may choose a vaginal breech or it may be the only option if they present in advanced labour
How should breech deliveries by conducted?
- ‘hands off breech’- putting traction on baby during delivery can cause fetal head to extend, getting it trapped during delivery
- support the fetuses pelvis anteriorly
- specific manoeuvres may be required: flexing fetal knees, lovsetts manoeuvre, MSV manoeuvre
List 3 complications of a breech presentation
- cord prolapse (cord drops down below the presenting part of the baby and becomes compressed)
- fetal head entrapment
- premature rupture of membranes
- birth asphyxia- usually secondary to delay in delivery
- intracranial haemorrhage- due to rapid compression of head during delivery
What is the definition of lie, presentation and position?
Lie: relationship between long axis of fetus and mother- londitudinal, transverse or oblique
Presentation: the fetal part which enters the maternal pelvis- cephalic, breech, shoulder, face or brow
Position: the position of the fetal head as it exists the birth canal- usually occipito- anterior, may be occipito- posterior or transverse
how are fetal lie and fetal position determined?
fetal lie and presentation by abdo exam
fetal position by vaginal examination during labour
- any suspicion of abnormality should get confirmed by USS
How is a brow and shoulder presentation managed?
- c section necessary
How is a face presentation managed?
- if chin is anterior (mento- anterior) a normal labour is possible however likely to be prolonged and increased risk of c section being required
- if chin is posterior then a c section is necessary
how are malpositions managed?
90% spontaneously rotate to occipito- anterior as labour progresses. If the fetal head does not rotate, rotation and operative vaginal delivery or c section can be performed
What is oligohydramnios
?
- low level of amniotic fluid
- below the 5th centile for gestational age
How and when does amniotic fluid get produced and absorbed?
- volume increases until 33 weeks and then plateaus at around 500ml
- produced by fetal urine output w/ small amount from placenta
- fetus breathes and swallows it, it gets processed and then voided out again
- any thing that disrupts production of urine, output of urine or rupture of membranes can reduce amniotic fluid
What may cause oligohydramnios?
- preterm prelabour rupture of membranes
- placental insufficiency (blood prioritised to brain rather than abdomen and kidney= low urine output)
- renal agenesis
- non functioning kidneys
- obstructive uropathy
- genetic/ chromosomal abnormalities
- viral infections
How is oligohydramnios diagnosed?
- USS
- amniotic fluid index or maximum pool depth, both have similar diagnostic accuracy but AFI more commonly used
How can ruptured membranes be tested for?
- actim prom- bedside test to detect IGFBP-1 in vagina
- this protein is found in amniotic fluid and if detected is strongly suggestive or membrane rupture
- particularly useful if diagnosis unclear
How should oligohydramnios be investigated?
- IGFBP-1 if suspect membrane rupture
- USS for structural abnormalities, renal agenesis and obstructive uropathy
- USS for fetal size- if small do umbilical artery doppler for placental insufficiency
- karyotyping if early unexplained oligohydramnios
how should ruptured membranes be managed?
- labour is likely to commence in 24- 48hrs
- if preterm, and labour doesnt automatically start then induction should be considered around 34-36 weeks if no infection
- course of steroids should be given to aid lung development and abx to reduce risk of ascending infection
What is the prognosis like for oligohydramnios?
- poor prognosis if in 2nd trimester as usually due to rupture of membranes (may be associated with infection) and so they get born very prem
- if due to placental insufficiency then also higher rate of prem
- fetus may develop severe muscle contractures despite physio after birth as low amniotic fluid reduces ability to move in utero
What is the definition of polyhydramnios?
Amniotic fluid index above the 95th centile for gestational age
What may cause polyhydramnios?
- idiopathic in 50-60%
- any condition affecting swallowing (oesphageal atresia, CNS abnormalities, muscular dystrophies, congenital diaphragmatic hernia
- duodenal atresia
- anaemia
- fetal hydrops
- twin to twin transfusion syndrome (disproportionate blood supply in twin pregnancies)
- increased lung secretions- cystic adenomatoid malformation of lung
- genetic or chromosomal abnormality
- maternal diabetes- esp if poorly controlled
- maternal ingestion of lithium (leads to fetal diabetes insipidus)
- macrosomia
How should polyhydramnios be invesgitaed?
- USS to detect anomalies in fetal size, doppler to detect fetal anaemia
- maternal glucose tolerance test for maternal diabetes
- karyotyping esp if abnormalities detected or fetus is small
- TORCH screen as some viral infections can cause
How should polyhydramnios be managed if the woman is experiencing symptoms eg breathlessness?
- aminoreduction can be considered but has infection and placental abruption risk so not routine
- indomethacin can be used to enhance water retention so reduced fetal urine output but is associsated with premature closure of ductus arteriosus so isnt used after 32 weeks
How should idiopathic polyhydramnios be managed after birth?
must be examined by paeds before first feed and an NG tube must be passed to ensure there is not a tracheoesphageal fistula or oesphageal atresia
What complications are more likely due to idiopathic polyhydramnios?
- preterm labour due to overdistension of uterus
- underlying abnormality or congenital malformation
- malpresentation more likely as baby more room to move
- higher risk cord prolapse
- higher incidence post partum haemorrhage as uterus has to contract further to achieve homeostasis
