14 - Fetal Abnormalities Flashcards
When is a fetus small for gestational age and how is this measured?
Measures below the 10th centile for their gestational age.
US: estimated fetal weight (EFW) and fetal abdominal circumference (AC)
Customised growth charts: depends on ethnicity, height, weight and parity of mother
What is classed as a low and high birth weight?
Less than 2500g is low
Over 4500g is high
What is the difference between small for gestational age and fetal growth restriction?
SGA means baby is small for dates without stating why, could be constitutionally small
FGR is SGA due to pathology so increased risk of complications
What are some causes of a fetus being small for gestational age?
- Constitutionally Small
OR
- Intrauterine Growth Restriction (FGR): can be placenta mediated or non-placenta mediated growth restriction
If a fetus is SGA, what signs point to it being FGR over being constitutionally small?
- Reduce amniotic fluid volume
- Abnormal doppler studies
- Reduced fetal movements
- Abnormal CTGs
What are the complications with fetal growth restriction?
Short term:
- Fetal death or stillbirth
- Birth asphyxia
- Neonatal hypothermia
- Neonatal hypoglycaemia
Long term
- CVD risk for baby
- T2DM risk for baby
- Obesity risk for baby
- Mood and behaviour problems for baby
What are some risk factors for a SGA fetus?
- Previous SGA baby
- Obesity
- Smoking
- Diabetes
- Pre-eclampsia
- Aged >35
- Multiple pregnancy
- Antepartum haemorrhage
- Antiphospholipid syndrome
How is SGA monitored for in pregnancy?
At booking appointment every woman risk assessed for potential of SGA
Low risk woman: Symphysis Fundal Height at every appointment from 24 weeks onwards and then plotted on growth chart. If less than 10th gentile booked for serial growth scans and umbilical artery doppler
High risk woman: serial growth scans and umbilical artery doppler
If a woman is being investigated for SGA, what measurements are taken?
- Estimated fetal weight and Abdominal Circumference to determine growth velocity
- Umbilical artery pulsatility Index (UA-PI)
- Amniotic Fluid Volume
How is SGA managed?
- Treat modifiable risk factors e.g stop smoking
- Serial growth scans to monitor
- Test for infections
- Karyotyping
- Early delivery if static growth to prevent still birth. Give corticosteroids before delivery
What are some causes of macrosomia/large for gestational age?
When estimated fetal weight above 90th centile
- Constitutional
- Maternal diabetes
- Previous macrosomia
- Maternal obesity
- Overdue
- Male baby
What are some of the risks of macrosomia to mother and baby?
Mother
- Shoulder dystocia
- Failure to progress
- Perineal tears
- Instrumental delivery or C-section
- PPH
- Uterine rupture
Baby
- Birth injury e.g Erbs, clavicle fracture, fetal distress
- Neonatal hypoglycaemia
- Obesity in childhood
- T2DM in adulthood
What investigations are done for a LGA baby?
US: exclude polyhydraminos and estimate fetal weight
OGTT: look for gestational diabetes
How is a LGA baby managed?
Most will have successful vaginal delivery but risk of shoulder dystocia so:
- Delivery on consultant led unit
- Access to an obstetrician and theatre if needed
- Active management of third stage
- Early decision for C-Section if needed
- Paediatrician attending birth
What is oligohydramnios?
Low level of amniotic fluid in pregnancy (below 5th centile)
Volume of fluid increases steadily up to 33 weeks, plataeus 33-38 weeks then declines so around 500mls at delivery
Anything causes issues with baby swallowing, fetal urine output or rupture of membranes causing leakage will lower amount of fluid
What are the causes of oligohydramnios?
- Preterm prelabour rupture of membranes
- Placental insufficiency: blood flow being redistributed to the fetal brain rather than the abdomen and kidneys
- Renal agenesis
- Non-functioning fetal kidneys
- Obstructive uropathy
- Genetic/chromosomal anomalies
- Viral infections
How is oligohydramnios diagnosed?
- History: Any fluid leakage/damp
- Exam: Symphysis fundal height, Speculum exam may show pool of fluid
- US: Amniotic Fluid index and Maximum Pool depth
- Karyotyping
How is oligohydramnios managed?
Ruptured Membranes
- Labour likely to commence in 24-48 hours
- If labour doesn’t start automatically, induction of labour should be considered around 34-36 weeks (in the absence of infection).
- Course of steroids should be given to aid fetal lung development
- Antibiotics to reduce risk of ascending infection
Placental Insufficiency
Aim for early delivery before 36-37 weeks
What are some of the complications of oligohydramnios?
Space limitations so:
Foetal compression: clubbed feet, facial deformity, muscle contractors and congenital hip dysplasia.
Underdevelopment of the lung and pulmonary hypoplasia: respiratory distress at birth
A combination of the above is Potter Syndrome
Preterm delivery
What is polyhydramnios and some causes of this?
Too much amniotic fluid above 95th centile. Too much urine or too little swallowing
- Idiopathic (60%)
- Any condition that prevents fetus from swallowing: e.g. oesophageal atresia, CNS abnormalities, muscular dystrophies
- Duodenal atresia: ‘double bubble’ sign on US
- Viral infections
- Fetal hydrops
- Twin-to-twin transfusion syndrome
- Increased lung secretions
- Genetic or chromosomal abnormalities
- Maternal diabetes
- Maternal ingestion of lithium: DM insipidus
- Macrosomia: larger babies produce more urine.
What are some investigations that can be done for polyhydramnios?
- US
- Doppler
- Karyotyping
- Test for TORCH infections
- OGTT for diabetes
How is polyhydramnios managed?
- Most need no medical intervention
- Amnioreduction: if maternal symptoms are severe (e.g breathlessness). Risk of infection and placental abruption
- Indomethacin: enhance water retention, and thus reduces fetal urine output. Do not use past 32 weeks as can prematurely close PDA
- If idiopathic baby needs to be seen by paediatrician before first feed. Needs NG tube passing to see if atresia or fistula
What are some complications with polyhydramnios?
Maternal
- Respiratory compromise due to increased pressure on the diaphragm
- Risk of UTI due to increased pressure on the urinary system
- Worse GORD
- Increased incidence of C section
- Increased risk of amniotic fluid embolism
Foetal
- Pre-term labour and delivery
- Premature rupture of membranes
- Placental abruption
- Malpresentation of the foetus
- Umbilical cord prolapse
What are the different types of breech presentation?
- Complete breech: legs fully flexed at the hips and knees
- Incomplete breech: one leg flexed at the hip and extended at the knee
- Extended breech: both legs flexed at the hip and extended at the knee
- Footling breech: foot is presenting through the cervix with the leg extended
What are some risk factors for a breech presentation?
How is breech presentation managed?
Up to 36 weeks:
Leave as most babies turn spontaneously
37 weeks (term):
- External Cephalic Version
- If this fails can be offered vaginal birth or C-section. Need obstetrician and access to theatre if vaginal
- If twins and presenting is breech need C-section
- If footling need C-section
How is external cephalic version does after a breech presentation at term is confirmed by US diagnosis?
Around 40-50% successful. Done under US guidance
- Analgesia
- Terbutaline SubCut: To allow tocolysis to relax uterus making it easier for the baby to turn.
- Anti-D prophylaxis: If woman is Rh-ve this is a sensitisation procedure. Kleihauer test to determine dose
What are some complications associated with external cephalic version?
- Transient fetal heart abnormalities
- Fetal bradycardia
- Placental abruption
What women is external cephalic version contraindicated in?
- Recent antepartum haemorrhage
- Ruptured membranes
- Uterine abnormalities
- Previous Caesarean section
What are some manoeuvres used in a breech vaginal birth?
- Hand off the breech - Prevent traction on head
- Flex fetal knees to enable delivery of the legs
- Lovsett’s manoeuvre to rotate body and deliver the shoulders
- Mauriceau-Smellie-Veit (MSV) manoeuvre to deliver the head by flexion. If fails use forceps
What are the complications of a breech presentation?
- Cord prolapse
- Fetal head entrapment
- Premature rupture of membranes
- Birth asphyxia
- Intracranial haemorrhage
What is the different types of lie, presentation and position?
Best is longitudinal lie, cephalic presentation and OA presentation
- Lie: Longitudinal, transverse or oblique
- Presentation: Cephalic, breech, shoulder, face and brow
- Position: OA, OP, OT
What are some risk factors for an abnormal lie, presentation or position?
- Prematurity
- Multiple pregnancy
- Uterine abnormalities (e.g fibroids)
- Fetal abnormalities
- Placenta praevia
- Primiparity
How do you determine the position of a baby?
Vaginal Examination during delivery to assess fontanelles
What are the different types of cephalic presentation?
- Vertex
- Face
- Chin
- Brow
What is prolonged pregnancy and what are some risk factors for this?
Pregnancy up to and beyond 42 weeks gestation
- Nulliparity
- Maternal age >40
- Previous prolonged pregnancy
- High body mass index (BMI)
- Family history of prolonged pregnancies
What are the complications of prolonged pregnancy?
Higher risk of stillbirth
Higher risk of meconium aspiration and instrumental delivery
Risk of neonatal hypoglycaemia
What are some clinical features of prolonged pregnancy?
- Static growth or macrosomia
- Oligohydramnios
- Reduced fetal movements
- Presence of meconium
- Dry / flaky skin with reduced vernix
How is prolonged pregnancy managed?
Offered membrane sweeps at 40 weeks then induction of labour at 41 weeks
Those that decline need twice weekly CTG monitoring and US. If signs of fetal distress need emergency C-section
What is placenta praaevia?
- Low-lying placenta is used when the placenta is within 20mm of the internal cervical os
- Placenta praevia when the placenta is over the internal cervical os
High risk of antepartum haemorraghe. Used to be graded but now only placenta praevia or low-lying placenta
What are the three main causes of antepartum haemorrhage?
- Placenta Praevia
- Placental Abruption
- Vasa Praevia
Minor bleeding: ectropion, infection, vaginal abrasions from intercourse
What are the complications of placenta praevia?
- Antepartum haemorrhage
- Emergency caesarean section
- Emergency hysterectomy
- Maternal anaemia and transfusions
- Preterm birth and low birth weight
- Stillbirth
What are some factors that increase the risk of placenta praevia occurring?
How is placenta praevia diagnosed?
Position of placenta assessed at 20 week anomoly scan
May present with painless vaginal bleeding, this is often in late pregnancy around 36 weeks
How do you assess antepartum haemorraghe?
History: see image
General Exam: Does the uterus feel tense? Cap refil? Assess fetal position. CTG.
Assessment of bleeding: Do not do speculum or vaginal exam until placenta praevia is ruled out with US. If only little bleeding take swabs for infection
What investigations should you do for any antepartum haemorraghe? e.g placenta praevia, placental abruption
IMPORTANT CARD TO MEMORISE
Bloods:
- FBC
- Clotting profile
- G+S
- Cross match
- Kleinbauer test if Rh-ve
- U+Es
- LFTs
Imaging
- CTG if >26 weeks
- US
How is placenta praevia managed if found on the 20 week scan?
- Repeat US: at 32 then 36 weeks
- Corticosteroids: at 34 weeks due to risk of preterm
- Planned C-Section: between 36-37 weeks. Use US before C-section to determine location of placenta and decide what incision to use.
If spontaneous labour before this do emergency c-section
What advice should you give a woman who has placenta praevia but is not bleeding?
- Bed rest
- No penetrative sexual intercourse
- Go to hospital if bleeding
The main risk with placenta praevia is haemorraghe, how is this managed if this occurs?
- Emergency caesarean section
- Blood transfusions
- Intrauterine balloon tamponade
- Uterine artery occlusion
- Emergency hysterectomy
What is placenta accreta and the different spectrums of this?
When the placenta implants deeper than the endometrium so it is difficult for the placenta to separate on delivery
- Accreta: implants in the surface of the myometrium, but not beyond
- Increta: attaches deeply into the myometrium
- Percreta: invades past the myometrium and perimetrium, potentially reaching other organs such as the bladder
What are some risk factors for developing placenta accreta?
What are some risk factors for developing placenta accreta?
- Previous placenta accreta
- Previous endometrial curettage procedures (e.g. for miscarriage or abortion)
- Previous c-section
- Multigravida
- Increased maternal age
- Low-lying placenta or placenta praevia
How does placenta accreta present?
- Usually asymptomatic but can present with antepartum haemorraghe in third trimester
- May be picked up on a Doppler US but not often
- Often presents during labour when difficult to deliver placenta, PPH risk
How is placenta accreta managed?
If diagnosed on US do MRI to see depth of invasion. Then plan C-Section at 35-36 weeks with abdominal hysterectomy. Give corticosteroids
If not discovered until a c-section, close woman back up and wait for specialist team to help
If not discovered until after birth do hysterectomy
At C-section can either do:
- Hysterectomy with the placenta remaining in the uterus (recommended)
- Uterus preserving surgery, with resection of part of the myometrium along with the placenta
- Expectant management, leaving the placenta in place to be reabsorbed over time
What is the risk with expectant management for placenta accreta?
- Bleeding
- Infection
What is placental abruption and the two types of this?
When the placenta separates from the wall of the uterus during pregnancy
Significant cause of antepartum haemorraghe (PV bleeding after 24 weeks)
Concealed or Reveal Abruption
What are some risk factors for placental abruption?
- Previous placental abruption
- Pre-eclampsia
- Bleeding early in pregnancy
- Trauma (consider domestic violence)
- Multiple pregnancy
- Fetal growth restriction
- Multigravida
- Increased maternal age
- Smoking
- Cocaine or amphetamine use
How may placental abruption present?
(important image)
- Sudden onset severe abdominal pain that is continuous
- Vaginal bleeding
- Shock (hypotension and tachycardia)
- Abnormalities on the CTG indicating fetal distress
- Characteristic “woody” abdomen on palpation, suggesting a large haemorrhage
How is the severity of placental abruption classified?
- Spotting:
- Minor haemorrhage: less than 50ml blood loss
- Major haemorrhage: 50 – 1000ml blood loss
- Massive haemorrhage: more than 1000 ml blood loss, or signs of shock
How is a placental abruption managed?
Clinical diagnosis based on presentation, EMERGENCY.
Initial Steps
- Urgent involvement of a senior obstetrician, midwife and anaesthetist
- 2 x grey cannula
- FBC, UE, LFT and coagulation studies
- Crossmatch 4 units of blood
- Fluid and blood resuscitation as required
- CTG monitoring of the fetus
- Close monitoring of the mother
- Antenatal steroids if between 24 and 34+6
- Anti D Prophylaxis if necessary
- Emergency C-Section if fetal distress or mother unstable
- Active management of the third stage as risk of PPH
For any antepartum haemorraghe what do you need to do?
If mother is rhesus negative need to give anti-D prophylaxis within 72 hours
What is Vasa Praevia?
Where the fetal vessels are within the fetal membranes (chorioamniotic membranes) and travel across the internal cervical os
Two umbilical arteries and one umbilical vein
What is the pathophysiology of vasa praevia?
Fetal vessels are outside of the placenta and umbilical cord so not offered protection
This is due to a multi loped placenta or due to umbilical cord inserting into the choramniotic membranes rather than the placenta
- Type I vasa praevia – the fetal vessels are exposed as a velamentous umbilical cord
- Type II vasa praevia – the fetal vessels are exposed as they travel to an accessory placental lobe
What is the issue with vasa praevia?
Vessels are prone to damage and bleeding, especially when membranes rupture and labour
Leads to fatal haemorraghe and death
What are some risk factors for developing vasa praevia?
- IVF
- Multiple pregnancy
- Low lying placenta
How does vasa praevia present?
Classic Triad:
- Painless vaginal bleeding
- Rupture of membranes
- Foetal bradycardia (or resulting foetal death)
How is vasa praevia managed?
Usually diagnosed antenatally by TVUS or during labour may see pulsating fetal vessels through membranes
- Corticosteroids, given from 32 weeks gestation to mature the fetal lungs
- Elective caesarean section, planned for 34 – 36 weeks gestation
After stillbirth or unexplained fetal compromise during delivery, placenta is examined for evidence of vasa praevia as a possible cause.
