Foetal health and growth

Question 1

What does SGA mean?

Answer 1

• This means that the weight of the foetus is less than the 10th centile for it gestation- if at term – 2.7kg, but other cut-off points can be used
• Assessment of foetal weight is better at identifying IUGR if customised according to what would be expected for the individual rather than the overall population

Question 2

What is IUGR?

Answer 2

• Describes foetuses that have failed to reach their own growth potential
• If a foetus was genetically determined to be a 4kg term and delivers at term weighing 3kg, its growth has been restricted and it may have placental dysfunction

Question 3

What is foetal distress?

Answer 3

refers to an acute situation that may result in foetal damage or death if it is not revered or if the foetus is not delivered urgently
eg. hypoxia
usually seen in labour

Question 4

What is foetal compromise?

Answer 4

• Describes a chronic situation and should be defined as when conditions for the normal growth and neurological development are not optimal
• Most identifiable causes involve poor nutrient transfer through the placenta (placental dysfunction)-
commonly there is IUGR, but this may also be absent eg. maternal diabetes or prolonged pregnancy

Question 5

What is foetal surveillance?

Answer 5

o	Identify the high risk pregnancy using history or events during pregnancy, or using specific investigations
o	Monitor the foetus for growth and well-being- the methods used will vary according to pregnancy risk and events during the pregnancy
o	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 6

What are the early pregnancy risks?

Answer 6

• Pregnancy-associated plasma protein A (PAPPA) is a placental hormone
the maternal level is reduced in the 1st trimester with chromosomal abnormalities
Used for Down’s, risk of IUGR, placental abruption, stillbirth
Maternal uterine artery doppler: abnormal wave forms suggest failure of development of a low resistance circulation (pre-eclampsia, IUGR, placental abruption)
most sensitive at 20-23 weeks, but can be used from 12 weeks to term

Question 7

What are the later pregnancy risks?

Answer 7

• With the occurrence of pre-elcampsia or vaginal bleeding

or if a routine abdominal palpation suggests a SFD foetus

Question 8

What is ultrasound used for?

Answer 8

to measure foetal size after the 1st trimester (abdo and head circumference)
Rate of growth using previous scans
Asymmetrical growth- a reduction in the rate of growth of the abdominal circumference by >30% is suggestive of IUGR
assessing actual growth according to expected growth

Question 9

What are doppler waveforms of the umbilical artery used for?

Answer 9

evidence of high resistance circulation suggests placental dysfunction
• Resistance is described according to end-diastolic flow (high or >95th centile), absent (AEDF) or reversed (REDF)
Identify growth restricted foetuses- best performed before 34 weeks as not sensitive alone after, but when used in conjunction with MCA or cerebroplacental ratio (CPR) it is better

Question 10

What are the doppler waveforms in foetal cerebral circulation used for?

Answer 10

• Doppler is used to assess the resistance or velocity of the MCA
with foetal compromise the MCA often develops a low resistance pattern in comparison to the thoracic aorta or renal vessels
the velocity of MCA flow also increases with foetal anaemia
• The ratio of the pulsatility index (PI) of this vessel compared to umbilical artery is the best method of assessing chronic placental dysfunction >34 weeks

Question 11

What are doppler waveforms of the foetal venous circulation used for?

Answer 11

• All major foetal vessels can be seen, but the most commonly measured is the ductus venosus
measure of cardiac function and used to assess extremely preterm foetuses (<28 weeks) as an alternative to CTG
It is useful in assessing disease severity in babies with heart failure and TTTS

Question 12

What is the cardiotocography or non-stress test?

Answer 12

• Foetal heart is recorded electronically for up to 1hr
accelerations and variability >5 beats/minute should be present, decelerations absent and the rate in the range of 110-160 bpm
• CTG gives immediate information about foetal status at >26 weeks, but are of no use as an antenatal screening tests

Question 13

What is the kick chart?

Answer 13

• The 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 14

Which factors are associated with SGA?

Answer 14

o	Low maternal height & weight
o	Nulliparity
o	Asian ethnic group
o	Female foetal gender
o	Pre-existing maternal disease- eg. renal or autoimmune disease
o	Maternal pregnancy complications- eg. pre-eclampsia
o	Multiple pregnancy
o	Smoking
o	Drug usage
o	Infections- eg. CMV
o	Extreme exercise
o	Malnutrition
o	Congenital abnormalities

Question 15

How is SGA diagnosed?

Answer 15

• Reduced foetal movements are not consistent with IUGR as this is a very late stage
• Serial measurements of the symphysis fundal height may be reduced or slow down
• The diagnosis of SGA is made using USS
• To tell which SGA foetuses are actually IUGR and how severely- USS and umbilical artery Doppler which >34 weeks are combined with MCA as the CPR are used
• A reduction in growth velocity by >30% of the abdominal circumference also suggests IUGR, the amniotic fluid volume is often reduced (oligohydramnios)- CTG is also used, but will become abnormal usually only when severe compromise or ‘foetal distress’ is present

Question 16

What is the management for SGA?

Answer 16

• Growth is rechecked with USS at 2-3 weekly intervals
at gestation >37 weeks delivery should be arranged, however, in some foetuses that are not very small (>3rd centile), with normal umbA and CPR Dopplers it may be more appropriated to wait until 40-41 weeks to allow labour to be spontaneous

Question 17

What is the management for IUGR?

Answer 17

• Gestation <34 weeks- aim is to prevent in utero demise or neurological damage associated with ongoing placental dysfunction, whilst maximising the gestation to avoid complications of prematurity, an estimated foetal weight for intervention need to be >500g and the gestation >25-26 weeks for a foetus to be viable once delivered
• An IUGR foetus with abnormal umbA Doppler values is reviewed at least twice a week- if AEDF is seen the mother is admitted and given steroids
if gestation is >32 weeks- C-section
<32 weeks a daily CTG is performed and delivery if this is abnormal
delivery <34 weeks- maternal administration of magnesium sulphate

Question 18

What are the causes of stillbirth?

Answer 18

o IUGR (SGA)- the most common with smoking and multiple pregnancy as important risk factors
o Unexplained cases- often due to the pathology behind IUGR
o Foetal and chromosomal congenital abnormalities- vary in incidence according to the level of prenatal diagnosis
o Pregnancy-related maternal disease- eg. pre-eclampsia, gestational diabetes, much of the risk is via placental disease
o Infection- GBS, parovirus or CMV
o Placental abruption
o Intrapartum- usually hypoxia
o Rare- foetal exsanguination, as foeto-maternal haemorrhage or vasa praevia, fatty liver and cholestasis

Question 19

What is a prolonged pregnancy?

Answer 19

> 42 weeks- the risk of perinatal mortality and morbidity rapidly rise between 41-42 weeks approx. 6% of pregnancies reach 42 weeks, more common if previous pregnancies have been prolonged and in nulliparous women
• The rate of stillbirth per 1000 continuing pregnancies rises from 0.35 at 37 weeks to 2.12 at 43 weeks- neonatal illness and encephalopathy, meconium passage and a clinical diagnosis of foetal distress are more common
• Sweeping of the cervix usually occurs at 40-41 weeks and helps to spontaneously start labour