Foetal Growth, Compromise and Surveillance

Question 1

What does small for gestational age mean?

Answer 1

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)

Question 2

What is the cause of SGA?

Answer 2

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.

Question 3

What is IUGR?

Answer 3

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

Question 4

what is foetal distress?

Answer 4

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

Question 5

What is foetal compromise?

Answer 5

Describes a chronic situation and should be defined as when conditions for the normal growth and neurological development are not optimal

Question 6

What is the cause of foetal compromise?

Answer 6

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

Question 7

What are the aims of foetal surveillance?

Answer 7

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

Question 8

When can risks be identified?

Answer 8

Pre-pregnancy
Early pregnancy
Late pregnancy

Question 9

What risk factors can be detected in pre-pregnancy?

Answer 9

No specific risk factors can be detected in pre-pregnancy

Question 10

What risk factors can be detected in early pregnancy?

Answer 10

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

Question 11

What is the significance of low PAPPA?

Answer 11

Down’s syndrome

Low level = high risk IUGR, placental abruption and consequent stillbirth

Question 12

What is the significance of abnormal wave forms / low resistance circulation in maternal uterine dopplers?

Answer 12

75% pregnancies at risk of adverse neonatal outcomes in early 3rd trimester

Particularly: early pre-eclampsia, IUGR or placental abruption

Question 13

When is maternal uterine artery Doppler most sensitive?

Answer 13

20-23 weeks - less predictive of later problems

most sensitive at 20-23 weeks but can be used from 12 weeks to term

Question 14

What factors can be identified in later pregnancy?

Answer 14

Pre-eclampsia, vaginal bleeding

SFD foetus

Question 15

Name some of the methods of foetal surveillance?

Answer 15

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

Question 16

What is USS used for?

Answer 16

Measure foetal size after the 1st trimester - particularly the abdominal and head circumference - these changes are recorded on centile charts

Question 17

What factors help to differentiate between healthy small foetuses and ‘growth restricted’ foetuses?

Answer 17

1. rate of growth - can be determined by previous scans or a later examination at least 2 weeks apart
2. 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
3. allowance for constitutional non-pathological determinants of foetal growth enables ‘customisation’ of individual foetal growth - assessing actual growth according to expected growth

Question 18

What threshold is suggestive of IUGR?

Answer 18

Reduction in abdominal rate of growth by >30%

Question 19

What is Doppler used for?

Answer 19

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

Question 20

How does cardiotocography work?

Answer 20

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

Question 21

How does a Kick chart work?

Answer 21

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

Question 22

How are foetal health and size determined?

Answer 22

Combination of genetic and acquired factors

Question 23

What are the constitutional determinants for growth and birth weight?

Answer 23

Low maternal wight and height
Nulliparity
Asian ethnic group
Female foetal gender

Question 24

What pathological determinants can affect foetal size?

Answer 24

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

Question 25

What are the complications of SGA?

Answer 25

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

Question 26

How is IUGR or SGA diagnosed?

Answer 26

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

Question 27

What is the management of SGA?

Answer 27

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.

Question 28

What is the aim of management of IUGR?

Answer 28

prevent in utero demise or neurological damage associated with ongoing placental dysfunction, whilst maximising the gestation to avoid complications of prematurity

Question 29

what is the threshold of estimated foetal weight for intervention for IUGR?

Answer 29

> 500g

gestation >25-26 weeks for a foetus to be viable once delivered

Question 30

How is an IUGR baby managed?

Answer 30

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

Question 31

How is a severely IUGR baby delivered?

Answer 31

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

Question 32

What is stillbirth?

Answer 32

When a foetus is delivered after 24 weeks of gestation showing no signs of life - 1 in 200 pregnancies

Question 33

What are the possible causes of stillbirth?

Answer 33

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

Question 34

What is the presentation of most antepartum stillbirths?

Answer 34

reduced or absent foetal movements

Diagnosis made using USS

Question 35

What is a prolonged pregnancy?

Answer 35

> 42 weeks

Question 36

What is the effect of prolonged pregnancy?

Answer 36

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

Question 37

What is the aim of management of prolonged pregnancy?

Answer 37

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