Foetal Growth, Compromise and Surveillance Flashcards
What does small for gestational age mean?
Small for gestational age is defined as a fetus that measures below the 10th centile for their gestational age. Two measurements on ultrasound are used to assess the fetal size:
Estimated fetal weight (EFW)
Fetal abdominal circumference (AC)
What is the cause of SGA?
Constitutionally small, matching the mother and others in the family, and growing appropriately on the growth chart
Fetal growth restriction (FGR), also known as intrauterine growth restriction (IUGR)
Fetal growth restriction (FGR), also known as intrauterine growth restriction (IUGR), is when there is a small fetus (or a fetus that is not growing as expected) due to a pathology reducing the amount of nutrients and oxygen being delivered to the fetus through the placenta.
What is IUGR?
Describes foetuses that have failed to reach their growth potential - their growth in utero has slowed and they may be SGA - some do not and many stillbirths of foetuses distressed in labour are of apparently normal weight
If a foetus was genetically determined to be a 4kg term and delivers weighing 3kd - growth = restricted and may have placental dysfunction
what is foetal distress?
Refers to an acute situation that may result in foetal damage or death if it is not reversed, of if the foetus is not delivered urgently e.g. hypoxia
usually seen in labour - however, most babies that subsequently develop cerebral palsy were not born hypoxic
What is foetal compromise?
Describes a chronic situation and should be defined as when conditions for the normal growth and neurological development are not optimal
What is the cause of foetal compromise?
Most identifiable causes involve poor nutrient transfer through the placenta (placental dysfunction)
commonly, there is IUGR, but this may be absent - e.g. maternal diabetes or prolonged pregnancy
What are the aims of foetal surveillance?
identify the high risk pregnancy using history or events during pregnancy, pr using specific investigations
Monitor the foetus for growth and well-being - the methods used will vary according to pregnancy risk and events during the pregnancy
Intervene (usually expedite delivery) at an appropriate time, balancing the risks of in utero compromise against those of intervention and prematurity - the latter is itself a major cause of mortality and morbidity
When can risks be identified?
Pre-pregnancy
Early pregnancy
Late pregnancy
What risk factors can be detected in pre-pregnancy?
No specific risk factors can be detected in pre-pregnancy
What risk factors can be detected in early pregnancy?
Maternal levels of PAPPA - reduced in first trimester with chromosomal abnormalities
Maternal uterine doppler -abnormal wave forms of uterine circulation suggest failure of development of low resistance circulations
What is the significance of low PAPPA?
Down’s syndrome
Low level = high risk IUGR, placental abruption and consequent stillbirth
What is the significance of abnormal wave forms / low resistance circulation in maternal uterine dopplers?
75% pregnancies at risk of adverse neonatal outcomes in early 3rd trimester
Particularly: early pre-eclampsia, IUGR or placental abruption
When is maternal uterine artery Doppler most sensitive?
20-23 weeks - less predictive of later problems
most sensitive at 20-23 weeks but can be used from 12 weeks to term
What factors can be identified in later pregnancy?
Pre-eclampsia, vaginal bleeding
SFD foetus
Name some of the methods of foetal surveillance?
Ultrasound assessment
Doppler Waveforms of the Umbilical Artery
Doppler waveforms of the foetal cerebral circulation
Doppler Waveforms of the Foetal Venous circulation
Cardiotocography or Non-stress test
Kick chart
What is USS used for?
Measure foetal size after the 1st trimester - particularly the abdominal and head circumference - these changes are recorded on centile charts
What factors help to differentiate between healthy small foetuses and ‘growth restricted’ foetuses?
- rate of growth - can be determined by previous scans or a later examination at least 2 weeks apart
- Patterns of ‘smallness’ - foetal abdomen will often stop enlarging before the head which is ‘spared’ - this results in a ‘thin foetus’ or ‘asymmetrical’ growth restriction
- allowance for constitutional non-pathological determinants of foetal growth enables ‘customisation’ of individual foetal growth - assessing actual growth according to expected growth
What threshold is suggestive of IUGR?
Reduction in abdominal rate of growth by >30%
What is Doppler used for?
TO measure velocity waveforms in the umbilical arteries - evidence of high resistance circulation suggests placental dysfunction - e.g. reduced/absent flow in foetal diastole compared to systole
Usage improvs perinatal outcomes in high risk pregnancy, while reducing intervention in those not compromised.
The absence or reversal flow in diastole sally predated CTG abnormalities and correlates with severe compromised
How does cardiotocography work?
Foetal heart is recorded electronically for up to 1 hour - accelerations and variability >5 beats/minute should be present, decelerations absent and the rate in the range of 110-160bpm
CTG gives immediate information about foetal status at >26 weeks, but are of no use as an antenatal screening tests
How does a Kick chart work?
Mother records the number of individual movements that she experiences every day - most compromised foetuses have reduced movements in the hours before demise - however, they only stop moving shortly before death so should not be used routinely
How are foetal health and size determined?
Combination of genetic and acquired factors
What are the constitutional determinants for growth and birth weight?
Low maternal wight and height
Nulliparity
Asian ethnic group
Female foetal gender
What pathological determinants can affect foetal size?
Pre-existing maternal disease e.g. renal or autoimmune disease Maternal pregnancy complications e.g. pre-eclampsia Multiple pregnancy Smoking Drug usage Infections - e.g. CMV Extreme exercise Malnutrition
Congenital abnormalities
What are the complications of SGA?
Fetal death or stillbirth
Birth asphyxia
Neonatal hypothermia
Neonatal hypoglycaemia
Growth restricted babies have a long term increased risk of:
Cardiovascular disease, particularly hypertension
Type 2 diabetes
Obesity
Mood and behavioural problems
How is IUGR or SGA diagnosed?
Serial measurements of the symphysis fundal height may be reduced or slow down
BP and urine must be checked as pre-eclampsia commonly co-exists
USS - investigations. Anomaly scan is reported - testing for CMV or chromosomal abnormalities with NIPT or amniocentesis
USS + umbilical artery Doppler - >34 weeks combined with MCA
Reduction in growth velocity >30% of abdominal circumference
Amniotic fluid volume often reduced
CTG used - become abnormal usually only when severe compromise or ‘foetal distress’ is present
What is the management of SGA?
Identifying those at risk of SGA
Aspirin is given to those at risk of pre-eclampsia
Treating modifiable risk factors (e.g. stop smoking)
Serial growth scans to monitor growth
Early delivery where growth is static, or there are other concerns
When a fetus is identified as SGA, investigations to identify the underlying cause
Early delivery is considered when growth is static on the growth charts, or other problems are identified (e.g. abnormal Doppler results).
This reduces the risk of stillbirth. Corticosteroids are given when delivery is planned early, particularly when delivered by caesarean section. Paediatricians should be involved at birth to help with neonatal resuscitation and management if required.
What is the aim of management of IUGR?
prevent in utero demise or neurological damage associated with ongoing placental dysfunction, whilst maximising the gestation to avoid complications of prematurity
what is the threshold of estimated foetal weight for intervention for IUGR?
> 500g
gestation >25-26 weeks for a foetus to be viable once delivered
How is an IUGR baby managed?
umbA Doppler values reviewed at least twice a week - if AEDF is seen, the mother is admitted and given steroids
If gestation is >32 weeks, a C-section is usual, but if <32 weeks a daily CTG is performed and delivery only arranged if this is abnormal
How is a severely IUGR baby delivered?
C-section
<34 weeks immediately preceded by maternal administration of magnesium sulphate
34-37 weeks: delivery can be deferred in the absence of severely abnormal Doppler values. delivery by induction or C-seciton if CTG abnormal
> 37 weeks: delivery indicated by induction or C-section if the CTG is abnormal
What is stillbirth?
When a foetus is delivered after 24 weeks of gestation showing no signs of life - 1 in 200 pregnancies
What are the possible causes of stillbirth?
Unexplained (around 50%)
Pre-eclampsia
Placental abruption
Vasa praevia
Cord prolapse or wrapped around the fetal neck
Obstetric cholestasis
Diabetes
Thyroid disease
Infections, such as rubella, parvovirus and listeria
Genetic abnormalities or congenital malformations
What is the presentation of most antepartum stillbirths?
reduced or absent foetal movements
Diagnosis made using USS
What is a prolonged pregnancy?
> 42 weeks
What is the effect of prolonged pregnancy?
Risk of perinatal mortality and morbidity rapidly rise between 41-42 weeks
rate of stillbirth per 100 goes from 0.35 at 37 weeks to 2.12 at 43 weeks
neonatal illness, encephalopathy, meconium passage and a clinical diagnosis of foetal distress = more common
What is the aim of management of prolonged pregnancy?
balance the risks of obstetric intervention against those of prolonged pregnancy
By 41-42 weeks, induction of labour is favoured and prevents 1 foetal death in every 500 women induced
Cervical sweep at 40-41 weeks
