Foetal growth, health and surveillance

Question 1

How can you try to tell the difference between a healthy small foetus and a IUGR foetus?

Answer 1

By looking at the serial ultrasounds during pregnancy. A healthy small foetus is likely to have been consistently in the tenth centile, whereas an IUGR foetus is likely to have started in a lower centile and dropped down to the 10th one.
Therefore a baby who was meant to be 4kg but born 3kg (normal weight), would be likely to have had IUGR.

Question 2

What is the definition of small for gestational age?

Answer 2

When the weight of the foetus is in the tenth centile for its gestation.

Question 3

What is the difference between foetal distress and foetal compromise?

Answer 3

Foetal distress is an acute situation, usually during labour.
Foetal compromise is chronic and is when conditions for normal growth and neurological development are not optimal.

Question 4

What is the likely pathological cause for small for gestational age?

Answer 4

Placental dysfunction - involves more nutrient transfer through the placenta.

Question 5

What does foetal surveillance aim to do?

Answer 5

1. Identify high risk pregnancy
2. Monitor foetus for growth and well-being
3. Intervene at an appropriate time (usually expedite delivery).

Question 6

What is PAPPA and what do its levels show?

Answer 6

PAPPA is pregnancy associated plasma protein A is a placental hormone.
The maternal level is reduced in the first trimester with chromosomal abnormalities. It is therefore used as a screening for Down’s syndrome.
Low levels also constitutes a high risk for IUGR, placental abruption and consequent stillbirth.

Question 7

Why is maternal uterine artery Doppler used and what does it predict?

Answer 7

It detects the level of resistance in normal pregnancy in the uterine arteries (normally low).
If the resistance is high, it predicts pre-eclampsia, IUGR or placental abruption.

Question 8

When can the maternal uterine artery Doppler be done and when is it most sensitive?

Answer 8

From 12 weeks.

Most sensitive between 20 and 23 weeks.

Question 9

What is measured externally to get foetal growth?

Answer 9

The top of fundus to pubic symphysis.

Question 10

What 2 ultrasound measurements are recorded on centile charts?

Answer 10

Head circumference and abdominal circumference.

Question 11

What 3 factors help to differentiate between the healthy small foetus and the ‘growth restricted foetus’?

Answer 11

1. serial measurements >2 weeks apart can show rate of growth.
2. In IUGR, the abdomen will often stop enlarging before the head and therefore an asymmetrical growth restriction is seen. If a reduction in growth rate of the abdominal circumference is >30%, it is suggestive of IUGR.
3. Assessing growth according to expected growth.

Question 12

What is the limitation of detecting IUGR with US with diabetic mothers?

Answer 12

Their foetus often has a larger abdomen and therefore IUGR asymmetrical growth would be harder to detect.

Question 13

How is umbilical artery high resistance categorised by Doppler?

Answer 13

Absent end-diastolic flow

Reversed end-diastolic flow

Question 14

When is umbilical artery doppler best performed?

Answer 14

Before 34 weeks

Question 15

What is used when Doppler umbilical artery is not sensitive enough?

Answer 15

After 34 weeks, it is used in conjunction with the middle cerebral artery (MCA)

Question 16

What patterns are seen in MCA artery for the conditions it is used to detect?

Answer 16

Foetal anaemia = higher flow (velocity is checked to assess pregnancies at risk of anaemia).
Foetal compromise = lower resistance in comparison to the thoracic aorta or renal vessels.

Question 17

What ratio is currently used to assess chronic placental dysfunction after 34 weeks?

Answer 17

Pulsatility index of the MCA to the pulsatility index of the umbilical artery.

Question 18

What is measured to check foetal cardiac function as an alternative to CTG?

Answer 18

Doppler waveforms of the ductus venosus.

Question 19

What is cardiotocography?

Answer 19

It is the recording of the foetal heart electricity for up to an hour.
Accelerations and variability (>5 beats/min) should be present, decelerations absent and the rate in the range of 110-160bpm.

Question 20

What is a kick chart?

Answer 20

The mother records the number of individual movements that she experiences every day.

Question 21

Why is a kick chart useful?

Answer 21

Because most compromised foetuses have reduced movements in the hours before demise. A reduction in foetal movement is an indication for more sophisticated testing.

Question 22

What are the limitations of kick charts?

Answer 22

Compromised foetuses stop moving only a short time before death.
High maternal anxiety.
May lead to unnecessary intervention.

Question 23

What different factors determine foetal size?

Answer 23

1. Constitutional determinants - low maternal height/weight, nulliparity, Asian ethnic group and female gender are all associated with smaller babies (without IUGR).
2. Pathological determinants - maternal disease (renal disease/autoimmune), maternal pregnancy complications (pre-eclampsia), multiple pregnancy, smoking, drug usage, infection (CMV), extreme exercise, malnutrition and congenital (inc. chromosomal) abnormalities.

Question 24

What are the complications of small for gestation?

Answer 24

Still birth
Foetal distress in labour
Neonatal admission
Long-term handicap
Preterm delivery (iatrogenic and spontaneous)
Maternal risks are greater (because pre-eclampsia may coexist and c-section is often used).

Question 25

What frequently co-exists with IUGR? How is this disease checked for?

Answer 25

Pre-eclampsia.

Checks for with urine analysis and blood pressure readings.

Question 26

What serial examination findings would be suggestive of IUGR or SGA?

Answer 26

Serial fundal to pubic symphysis length measurements may be reduced or slow down.

Question 27

What investigation is used to diagnose SGA?

Answer 27

Ultrasound.

Question 28

What investigations are used to try and find the cause of SGA?

Answer 28

Non-invasive prenatal investigations to look for infection (CMV) or chromosomal abnormalities.
Amniocentesis could be considered as well.

Question 29

What investigations would you used to tell which SGA foetuses have IUGR and how severe this is?

Answer 29

Ultrasound - reduction in size of abdominal cavity of >30% is suggestive of IUGR.
Umbilical artery Doppler
After 34 weeks you combine the above with MCA Doppler.

Amniotic fluid is often reduced (oligohydramnios).

Question 30

How is SGA managed?

Answer 30

Serial ultrasounds every 2-3 weeks.
At 37 weeks gestation you would arrange delivery.
However, if foetus is >3rd centile, with normal umbA and CPR Dopplers then you would consider waiting until 40-41 weeks gestation to allow birth to be spontaneous.

Question 31

How is IUGR managed?

Answer 31

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

IUGR foetus + abnormal umbA = reviewed x2 weekly and if absent end-diastolic flow the mother is admitted and given steroids.

If >32 weeks = delivery by c-section.
If <32 weeks = daily CTG and delivery if this is abnormal.

Delivery before 34 weeks should be immediately preceded by magnesium sulphate (foetal neuroprotection and maternal protection against seizures).

Question 32

What is the definition of a stillbirth?

Answer 32

When a foetus over 24 weeks old shows no signs of life.

Question 33

What is the most common cause of stillbirth? What else causes it?

Answer 33

IUGR - whether that is the main cause or some other pathology behind it.
Foetal chromosomal abnormality.
Pre-existing maternal disease e,g, diabetes, autoimmune, renal.
Pre-eclampsia, gestational diabetes.
Infection.
Placental abruption.
Intrapartum, usually hypoxia

Question 34

What is prolonged pregnancy?

Answer 34

When 42 weeks gestation has been completed.

Question 35

What are the risks of prolonged pregnancy?

Answer 35

Neonatal illness and encephalopathy
Meconium passage
Foetal distress
Stillbirth

Question 36

What is the management of prolonged pregnancy?

Answer 36

From 41 weeks - offer induction as this reduces the risks from prolonged pregnancy and also reduces the likelihood of caesarian section being required.

If no induction - sweep cervix and arrange daily CTG.

If CTG is abnormal - deliver whatever the condition of the cervix, by c-section.

Question 37

What investigations are used if the foetus is <34 weeks and >34 weeks?

Answer 37

<34 weeks = umbilical artery Doppler

>34 weeks = umbilical artery and middle cerebral artery (cerebroplacental ratio)