Intrauterine Growth Restriction ✅ Flashcards
Why is an infant’s gestation and birth weight important?
It influences the nature of the medial problems likely to be encountered in the neonatal period
What is low birth weight defined as?
<2.5kg
What % of babies in the UK have low birth weight?
7%
What % of neonatal deaths are accounted for by babies with low birth weight?
Around 70%
What is small for gestational age defined as?
Babies with birth weight below the 10th centile for their gestational age
What is true of the majority of infants born SGA?
They are normal, but constitutionally small
What are the potential scenarios resulting in SGA babies?
- Have grown normally but are small
- Have experienced intrauterine growth restriction, i.e. have failed to reach their full genetically determined growth potential
How do babies with IUGR appear?
Thin and malnourished
Are all IUGR babies SGA?
No, babies with a birth weight above the 10th centile may be growth restricted, e.g. a fetus growing along 80th centile who develops growth failure and falls to 20th centile
What is the term SGA sometimes restricted to?
Babies whose birth weight falls below the 2nd centile
Why is the term SGA sometimes restricted to babies with birth weights below the 2nd centile?
Because the incidence of congenital abnormalities and neonatal problems is higher in these babies
What can fetal centiles be customised to take into account?
- Maternal characteristics
- Gestation
- Gender
What maternal characteristics might fetal centiles be customised on the basis of?
- Weight
- Height
- Parity
- Ethnicity
What is the advantage of customising fetal centiles?
More predictive of morbidity and mortality
What does the use of the term ‘intrauterine growth restriction’ to describe a fetus imply?
Pathological restriction of genetic growth potential
How can IUGR be identified/monitored?
Looking for evidence of fetal compromise
What evidence of fetal compromise might be identified in IUGR?
- Reduced liquor volume
- Abnormal Doppler waveforms
What has IUGR traditionally been classified as?
Symmetrical or asymmetrical
What is the more common type of IUGR?
Asymmetrical
What is meant by asymmetrical growth restriction?
The weight or abdominal circumference lies on a lower centile than that of the head
What causes asymmetrical IUGR?
When the placenta fails to provide adequate nutrition late in pregnancy
Why is brain growth spared at the expense of in asymmetrical IUGR?
- Liver glycogen
- Skin fat
What can cause the uteroplacental dysfunction leading to asymmetrical IUGR?
- Maternal pre-eclampsia
- Multiple pregnancy
- Maternal smoking
- Idiopathic
What happens to asymmetrical IUGR infants after birth?
They rapidly put on weight
What happens in symmetrical growth restriction?
The head circumference is equally reduced
What does symmetrical growth restriction suggest?
A period of poor intrauterine growth starting in early pregnancy
What is symmetrical growth restriction usually due to?
A small but normal fetus
What are the pathological causes of symmetrical IUGR?
- Fetal chromosomal disorder or syndrome
- Congenital infection
- Maternal drug and alcohol abuse
- Chronic medical condition or malnutrition
What happens to infants with symmetrical IUGR after birth?
They are more likely to remain small permanently
What is a fetus with IUGR at increased risk of?
- Intrauterine hypoxia/intrauterine death
- Asphyxia during labour and delivery
What is the purpose of close monitoring of an IUGR fetus?
Determine the optimal time for delivery
What does progressive uteroplacental failure result in?
- Reduced growth in femur length and abdominal circumference
- Reduced amniotic fluid volume
- Abnormal umbilical artery Doppler waveform
- Redistribution of blood flow in the fetus
- Abnormal ductus venosus Doppler waveform
- Reduced fetal movements
- Abnormal CTG
- Intrauterine death or hypoxic damage to the fetus
What causes the abnormal umbilical artery Doppler in progressive uteroplacental failure?
Increased placental impedance
What is found on umbilical artery Doppler in progressive uteroplacental failure?
Absent and then reversed end-diastolic flow velocity
How is blood redistributed when there is progressive uteroplacental failure?
Increased to brain, reduced to GI tract, liver, skin, and kidneys
What does the abnormal ductus venosus Doppler waveform in progressive uteroplacental failure?
Diastolic cardiac dysfunction
What are the risks/complications of IUGR after birth?
- Hypothermia
- Hypoglycaemia
- Hypocalcaemia
- Polycythaemia
Why are IUGR babies at risk of hypothermia after birth?
Because of their relatively large surface area
What is polycythaemia defined as?
Venous haematocrit >0.65
How does the umbilical artery Doppler waveform appear in the healthy fetus?
Forward flow in the umbilical artery throughout systole and diastole
How does the umbilical artery Doppler waveform appear in IUGR due to placental disease?
Reduced, then absent or reversed flow during diastole
What causes the abnormal umbilical artery Doppler in IUGR due to placental disease?
Increased resistance in the placenta due to loss of placental villi or pre-eclampsia
What is indicated if end-diastolic flow is absent on umbilical artery Doppler in IUGR?
Detailed Doppler studies of the middle cerebral artery and ductus venosus
What happens to blood flow as IUGR becomes increasingly severe?
There is redistribution of fetal blood flow, with an increase in flow to the brain and increased end-diastolic velocity
What should evidence of cerebral redistribution in a fetus indicate?
A need for invasive regular monitoring
What does a ductus venosus Dopper reflect?
The physiological state of the right heart
What may be found on ductus venosus Doppler in IUGR?
Reversed flow during atrial contraction (in the second trimester)
What does reversed flow during atrial contraction in a second trimester IUGR represent?
Cardiac decompensation
Why is ductus venosus Doppler a useful test?
Finding of reversed flow during atrial contraction is a better predictor of stillbirth than umbilical artery Doppler alone
What is timing of delivery based on in IUGR?
- Doppler findings
- Gestation
- Estimated fetal weight
