Complicated pregnancy: Abnormal fetal development Flashcards
Abnormal growth and amniotic fluid volume Reduced fetal movements and intrauterine death
What are the objectives/purpose for prenatal diagnosis?
- Detect life threatening or lethal abnormality / abnormality that causes severe mental handicap
- To arrange planned care for diagnosis
- To give option of TOP to parent(s)
How are prenatal fetal abnormalities diagnosed?
History taking
Maternal serum screening
Ultrasound
Invasive procedures
What should you ask in a history for prenatal fetal abnormalities?
Patient details:
* maternal age
* consanguinity - i.e. married to relative or child of parents who have same ancestor
* parents with known balanced translocation
PMH
* maternal diseases - DM? epilepsy?
* Any intrauterine infections? Rubella, CMV, ZIka, Parovirus
Previous obstetric Hx
* previous child with aneuploidy
* genetic disorder
* structural abnormality
DH
* any exposure to any drugs that can cause malformations - antiepileptics? warfarin? vitamin A?
You are in the prenatal diagnosis clinic for fetal abnormalities. What maternal blood screening do you offer?
- haemoglobinopathy: thalassaemia, sickle cell disease
- VDRL screening - this tests for syphilis
- HIV, hep B
- Maternal rhesus antibody
- combined first trimester serum screening - for Trisomy 21, 18 and 13
Between 11 and 20 weeks, what screening is done?
Combined 1st trimester screening = fetal nuchal transluceny (NT), PAPP and bHCG
Serum screening
In 2nd trimester = serum screening and 20 week anomaly scan. Integrated screening - which involves scan and blood test
Describe first trimester combined screening
- Assess risk being born with Down’s (Trisomy 21), Edwards (T18) and Patau’s (T13)
- is given for both singleton and twin pregnancy
- given as an option to women to choose to have screening for all 3, for just downs, or just edward’s and patau’s
What is antenatal ultrasounds used for?
- Dating of pregnancy
- Nuchal translucency
- look at fetus response to raised maternal AFP
- Routine anomaly scan
- check if small for date, look for polyhydraminos, oligohydraminos, reduced fetal movements
Main reasons for doing a 1st trimester ultrasound?
- check viability
- accurate dating of pregnancy
- twin determination and chorionicity
- detect any fetal abnormalities - e.g anencephaly, large anterior abdo wall defects, cystic hygroma
- measure nuchal translucency
A detailed Ultrasound scan is done between 18-20wks. What does this check for?
- viability
- measurements of growth
- liquor volume (the volume of fluid around the baby)
- fetal anatomy
- placental location
- assessment of normal variants for aneuploidy (chromosomal abnormalities) and fetal growth
What should you report from a scan (when looking at normal varient screening)?
- If nuchal fold is >6mm
- If there is ventriculomegaly >10mm
- Echogenic bowel (bowel shows up as bright as bone on scan)
- Renal pelvis dilatation (could be fetal hydronephrosis)
- Size < 5th centile on national charts
Following an USS of fetus, if you suspect a fetal abnormality, what can you do next?
Invasive procedures
Name some invasive procedures that can be done following abnormal findings in fetal scan
Amniocentesis
Chorion villus sampling
Fetocide
Aspiration from fluid filled fetal cavities
Amnioreduction/amniodrainage
What is amniocentesis?
Take sample of amniotic fluid and testing it
What is chorion villous sampling?
Take sample of placental tissue (the choronic villus) and test it
What are indications for amniocentesis or chorion villous sampling?
Assess fetal karotype (chromosome make up) because of:
- maternal age
- high risk for aneuploidy screening
- abnormal ultrasound findings
- parental translocation
- maternal request
Molecular genetic testing:
- autosomal dominant/recessive conditions
Virology screeb
- to assess for fetal infections - CMV
Describe amniocentesis
- weeks of gestation?
- how is it done?
- what’s done with sample?
- Ideally done after 15wk gestation
- To be performed under direct USS guidance
- 15-20 ml aspirated using a 22G needle
- From this aspirate, get culture of amniocytes, harvesting and anding - do PCR/FISH
What are risks of amniocentesis you should inform parents about before procedure?
- Risk of miscarriage - 0-5-1%
- risk of preterm delivery
- risk of chronic liquor leak
Describe chorion villus sampling
- weeks of gestation?
- how is it done?
- what is done with sample?
- after 10 weeks ideally
- USS guided with continuous visualisation of needle tip
- Transabdominal/transcervical
- sample is sent for cytogenics/molecular genetics
What risks of chion villus sampling should you inform parents about before the procedure?
- risk of miscarriage is 1%
- risk of culture faiure is 1%
- risk of mosaicism 1% (i.e. can get mitotic mutations in chromosomal makeup during development)
What is fetocide?
(sometimes spelt feticide)
Termination of pregnancy following fetal abnormality
Usually detected at anomaly scan at 20-22wks gestation
What is preimplantation genetic diagnosis (PGD)?
Analyse individual blastomeres of the embryo in 8 cell stage or in polar body of oocyte
Usually done for v difficult and complex situations in families with X linked conditions
Indications for preimplantation genetic diagnosis (PGD)?
- when there is known balanced parental translocation
- increased materal age
- familial history of x linked recessive disorders
What is non-invasive prenatal diagnsosis?
- check fetal genome
- by identifying and analysing fetal cells that are in the maternal circulation or free fetal DNA in the maternal plasma
- less invasive
- can predict fetal rhesus phenotype from maternal plasma
- can predict fetal sex
- can detect any fetal aneuploidy (abnormal chromosomes)
When looking at scan of miltple pregnancy, what should we look for?
- chorionicity
- fetal gender
- number of plaentas
- characteristics of membrane between two amniotic sacs (if two are present)
- nuchal translucency measurement
- fetal abnormality
What sign would you see in dichorionic diamniotic twins? picture below:
Lambda sign
What is twin-to-twin transfusion syndrome?
a prenatal condition in which twins share unequal amounts of the placenta’s blood supply resulting in the two fetuses growing at different rates.
5-15% are monochorionic twins
without treatment = 80-100% mortality
surviors have high risk of being handicapped
How can fetal growth be assessed in the antenatal period?
2 clinical examination methods are used:
- abdo palpation of fundal height - this does not have high sensitivity (20-30%)
- symphysis-fundal height measurement using a measuring tape
USS assessment - look at head circumference, abdo circumference, femur length (these are key anthropometric measurements). Sensitivity = 90-95%
From what gestational age is symphysis-fundal height measurment done ?
24 weeks
Define small for dates /SGA
Describes anthropometric variables below the 10th population centile for gestational age.
Does to imply presence or absence of pathology
Based on gestational population centile chart
Define large for dates / LGA
Describes anthropometric variables above the 95th population centile for gestational age
Does to imply presence or absence of pathology
Based on gestational population centile chart
Main reason for small babies?
Fetal growth resistriction
What is a growth restricted fetus?
One that has failed to reach its genetic growth potential
What are RFs for fetal growth restriction?
see pic.
Note: Placental pathology is not really a risk factor you can determine at booking. .
Infecton e.g. CMV
White column = preexisting disorders.
When referred a pt with a small baby, what steps need to be undertaken?
- confirm the dx - is the fetus really small
- etsblish cause - why is the fetus small
- management plan - how will you monitor the preg?
- weigh up risks and benefits - timing and mode of delivery
How will you confirm restricted fetal growth?
- confirm dates of pregnancy
- assess growth by USS
- review measurements
Considering ‘why is the fetus small?’, define:
Normal small
Abnormal small
Infected small
Starved small
Wrong small
- Normal small: constitutional, healthy. Symmetrical measurements throughout (follow growth chart)
- Abnormal small: chromosomal abnormalities, syndromes, congenital malformations
- Infected small: mother had infection during pregnancy (usually CMV)
- Starved small: a ‘placental FGR’ due to poor placentation - can be from smoking, maternal disease that affects the placenta, multiple pregnancy. This one is MOST important in Obstetrics, and is most common.
- Wrong small: incorrect dates or measurements
The placenta is important for a fetus’s growth. What does adequate trans-placental transfer depend on?
- uteroplacental blood flow - from uterine artery to placenta
- villous structure at the interface between maternal and fetal blood
- fetoplacental blood flow - from umbilical arteries to the placenta
The placenta and its formation is key for growth of fetus. **How can we investigate that the placenta has got successful trophoblast invasion ** (i.e. to be a healthy placenta for baby)?
Do a uterine artery doppler at 20-24 weeks to check flow of blood. need adequate flow to allow for normal placental function to support fetal growth.
normally - there should be low resistance, with a characterstic waveform of early diastolic notching.
On an ultrasound scan, how do you differentiate normal small from fetal growth restriction?
Take additional sonographic measures:
* centile position - lower the centile, more likely that the baby has a FGR compared to just being normal small - e.g baby in 1st centile could be normal small but is more likely to have a fetal growth restriction.
* Symmetry - if baby is asymmetrical where head is in 50th centile but adomen is in 10th centile (note: liver makes up large proportion of abdomen) = means liver is not functioning properly - there is some sort of growth restriction.
* Liquor volume - under perfused fetus = reduced kidney function = redued liqour volume = likely to be FGR
* UMA Doppler = with increased resistance, see more FGR
* Growth velocity = if baby is in 80th centile, but continues in 80th centile, they are a normal size baby. But if a starts in the 50th centile, then at the next scan, she is in the 10th, this means the baby is likely to be compromised.
Differential Diagnosis for fetal growth restriction?
how can you differentiate between these?
A healthy small baby
Aneuploidy / infection
Placental IUGR (intrauterine growth restriction)
Is this an adequate growth chart?
Yes - growth stays consistent on the centile growth line.
Is this an adequate growth chart?
No - baby goes from 80th centile and drops to about 40th centile at 34ish weeks (baby crosses centiles so something has happend to affect growth velocity.).
Is this an adequate growth chart?
Started off well - baby is growing well, BUT then stops putting on weight between 34th week - 36weeks - not a good sign
A woman has this scan. What would be your next steps?
Scan is at 28wks.
Baby is below 10th centile. So need to look at:
- maternal variables
- amniotic fluid volume
- doppler
- monitor baby from now on.
When we know a baby is small, how shall we go about monitoring the rest of the pregnancy?
Maternal monitoring
- assess for modifiable risk factors like smoking, alcohol
- assess for presence of maternal disease
- continue monitoring for pre-eclampsia, with blood pressure and urine checks, in regular intervals
Fetal surveillance
- serial growth measurements every 2-4 weeks
- fetal wellbeing surveillance:
- - > maternal perception of fetal movements
- - > fetal doppler
- - > amniotic volume measurements
- - > biophysical profile
Describe the benefits of umbilical artery doppler as a surveillance tool for fetal growth
- There is evidence of reduction in perinatal morbidity and mortality in high risk populations
- there were reductions in obstetric interventions
- there were reductions in use of resources compared to when a CTG was used on its own.
When are uterine dopplers used and when are umbilical dopplers used?
- Uterine doppers are useful for screening at 20weeks, where notching IDs high risk patients. Uterine is not useful for surveillance.
- Umbilical dopplers are essential for the surveilance of growth restricted fetus. Here, end-diastolic flow velocity (continous, absent, reversed) reflects the increase in placental resistance.
With abnormal fetal growth, what factors does mode of delivery depend on?
Gestation
Presentation
Fetal condition
Maternal factors
Whwn umbilical artery doppler is normal, when should delivery be?
Delay delivery until at least 37weeks
An umbilical artery doppler with absent or reversed end diastolic flow, when should you plan delivery?
Consider delivery >34/40 even in presence of normal additional assessmnet
Deliver before 34weeks if CTG abnormal, BPP abnormal or other Doppler parameters are abnormal (MCA, umbilical vein)
What risks after delivery of a FGR baby?
Higher risk of perinatal death
Increased need for resuscitation
Hypothermia and Hypoglycaemia
RDS and NEC
Neurodevelopmental delay
Cerebral palsy
Adult disease
A largw baby can cause an increased symphysis fundal height. What are DDx for large baby?
Uterine fibroids
Pelvic mass pushing up the uterus
Polyhydraminos
Maternal obesity
What are maternal factors for a large fetus?
DM
Obesity
Increased maternal age
Multiparity
Large stature
What are fetal factors for a large baby?
Constitutional
Male gender
Postmaturity
Genetic disorders - Beckwith Wiedeman
What are maternal risks associated with having a large baby?
Prolonged labour
Operative delivery
PPH
Genital tract trauma
What are fetal risks/neonatal/childhood associated with large baby?
Birth injury
Perinatal asphyxia from difficult delivery
Shoulder dystocia/Erb’s palsy
Hypoglycaemia
Childhood obesity
Metabolic syndrome
What is done when you find a large fetal baby? (i.e. what are next steps)
Pt 34 weeks pregnant, presents with reduction in feta, movements, what are the next steps?
Auscultation of fetal heart
THEN
CTG
when do fetal movements tend to plateau?
at 32wks gestation. There is no reduction in the frequency of fetal movements in the late third trimester
when are mothers usually aware of fetal movements?
by 20wks gestation
What is reduced fetal movement a sign of?
A warning sign of impending fetal death
What factors can affect a woman’s perception of fetal movements?
- anterior placed placenta - decrease perception of fetal movements
- sedating drugs which cross the placenta - e.g alcohol, benzodiazepines, methadone, opiods
- cigarette smoking - reduced fetal activity
- corticosteriods used for lung maturation - reduced fetal movements
- fetuses with major malformations
How are fetal movements assessed?
- maternal perception
- doppler or real time ultrasound
How should redued fetal movements be managed?
- exclude fetal death - auscultate fetal heart using Doppler handheld device
- then exclude fetal compromise
- Assess RFs in woman that are associated with adverse pregnancy outcomes - by taking a hx:
* do they have RF for stillbirth –>fetal growth restriction, HTN, small for gestational age, placental insufficiency, congential malformation, past obs Hx with stillbirth
If no RFs, gfetal movements are normal and fetal heart has been heard = no further intervention required.
If fetal movements reduced and/or RFs are identified = do CTG if over 28weeks
If CTG is normal but fetal movements still reduced/RFs present = refer for fetal growth scan and amniotic fluid volume in 24hrs.
How do you manage recurrent reduced fetal movements?
Senior review needed
Management for woman at 40weeks who has redued fetal movements?
Induction of labour is recommended
Differentials for reduced fetal movements?
Intrauterine death (stillbirth)
Fetal sleep
Congential fetal malformations
Fetal anaemia
Placental insufficiency - oligohydraminos or fetal growth restriction
Polyhydraminos
Anterior placenta
Maternal sedating drugs that cross the placenta
Maternal smoker
Corticosteriod administration for lung maturation
Busy mother who has not concentrated on fetal activity
Acute or chronic fetomaternal haemorrhage
A woman has suspected fetal compromise, as she has a ‘non reassuring CTG’. What would be present on this CTG? (slide 34 of labour and delivery lecture)
- baseline tachycardia or bradycardia
- reduced baseline variability (flat)
- absence of accelerations
- presence of decelerations - decreases in the FHR below the baseline, of more than 15 bpm in amplitude, and lasting more than 15 seconds
What are signs of suspected fetal compromise?
Non-reassuring CTG (baseline tachy or brady, reduced baseline variability, absence of accelerations, presence of decelerations)
Passage of meconium
A woman has suspected fetal compromise. She has a CTG done.
CTGs have high sensitivity but low specificity. What can you do next to confirm fetal compromise?
Fetal acid-base status via fetal scalp blood sampling.
If can not do this, deliver baby by speediest route
Causes of suspected fetal compromise?
Uterine hyperstimulation
Hypotension
Poor fetal tolerance of labour
Cord compression
Infection
Maternal disease
A woman is pregnant and her baby is in a breech presentation. What are risks of this for fetal development?
Increased perinatal morbidity/mortality
Higher incidence of fetal abnormality and neuro-developmental problems
Complications of delivery for fetus in breech presentation?
Trapped aftercoming head
Cord prolapse
Intracranial haemorrhage
Internal injuries
What are delivery options for breech presentation?
External cephalic version (try and turn baby over during vaginal delivery)
Elective C section
Vaginal breech delivery
Management for woman with suspected fetal compromise?
Rectify reversible causes - e.g. maternal hypotension
Left lateral position
Stop oxytocics - if these were given, as they overstimulate the uterus
Confirm compromise by fetal blood sampling
Deliver ASAP if can not correct or if there is significant acidosis.
Define stillbirth
Baby born dead after (but were alive at) 24 weeks completed gestation
Causes of stillbirth?
- No cause found
- Placental cause
- Antepartum or intrapartum haemorrhage
- major congenital abnormality
- infection
- hypertension in pregnancy
- maternal disease (renal related, DM)
- IUGR - intrauterine growth restriction
- mechanical cause - cord prolapse, knot in cord.
How is stillbrith (intrauterine death) diagnosed?
- mother will report reduced fetal movements
- no fetal heart sounds heard on hand held doppler (this can be unreliable)
Diagnose by absent fetal heart beat on US by 2 independent practitioners
How is stillbirth managed?
- if mother is Rh-ve = give anti-D
- Do Kleihauer testing on all women to dx fetomaternal haemorrhage as cause of stillbirth, and to determine anti-D dose
- check maternal temp, BP, urine for protein, blood clotting screening
- if have pre-eclampsia, abruption, sepsis, coagulopathy or membrane rupture = advise delivery
- if safe, mother may want to go home to reflect
- if not induced in 48hrs, check for coagulopathy twice weekly
- Induce labour with mifepristone orally and add prostaglandin vaginally
- ensure pain relief in labour
What maternal tests would you do to establish the cause of a stillbirth?
- Kleihauer - to determine if there is fetal blood in maternal circulation
- FBC
- CRP
- LFT
- TFT
- HbA1C and glucose
- blood culture
- viral screen - TORCH = Toxiplasmosis, Other, Rubella, CMV, Herpes
- Thrombophillia screen
- antibody screen - anti-red cell, anti-Ro, anti-La
- MSU
- Cervical swabs
