IUGR and SGA

Question 1

What is the definition of IUGR?

Answer 1

Failure of foetus to reach full growth potential

Question 2

What is the definition of SGA?

Answer 2

When the estimated foetal weight (or abdo circumference) is <10th centile or >2 SD from normal at same gestation

Question 3

What are the two main categories that cause IUGR?

Answer 3

Intrinsic - related to the foetus

Extrinsic - related to maternal factors and placental factors

Question 4

What are foetal factors causing IUGR?

Answer 4

Aneuploidy and other genetic conditions (i.e. Turners, trisomy)
Congenital abnormalities/malformations (i.e. cardiac defects)
Infection - CMV, toxoplasma, varicella and ?rubella

Question 5

What are maternal factors causing IUGR?

Answer 5

Affecting blood and vasculature

• anaemia
• PVD, CVD, HTN
• Thrombophilias and acquired VTE risk factors i.e. immobility, antiphospholipid syndrome

Affecting oxygenation - respiratory conditions i.e. asthma

Affecting nutrients - diabetes, malnutrition

Toxin exposures - narcotics, cocaine, alcohol, smoking

Question 6

What are placental causes of IUGR?

Answer 6

Multiple pregnancy - monochorionicity
Placental abnormalities
Placental abruption

Question 7

What are factors that help determine between SGA and constitutional small size?

Answer 7

Favour constitutional small size

• Normal amniotic fluid volume
• Normal doppler velocity of umbilical artery
• Parental short stature/genetic hx
• Normal growth trajectory

Question 8

How is IUGR screened for and detected?

Answer 8

Symphyseal-fundal heights and routine antenatal visits

Confirmed with U/S - ideally serial measurements

Question 9

What are the landmarks/characteristics for symphyseal-fundal height measurements?

Answer 9

Used from weeks 16-36 gestation (less accurate after 36 as fundal height regresses)

Landmarks - pubic symphysis at 10W, umbilicus at 12W and xyphisternum at 36W

Between umbilicus and xyphisternum, each finger/cm correlates to gestation +/- 3cm

Question 10

What influences the reliability of symphyseal-fundal height measurements?

Answer 10

More reliable if performed by same person

Less reliable if maternal obesity and multiple pregnancy

Question 11

When is IUGR diagnosed and which general causes are usually associated?

Answer 11

Early onset (2nd trimester/early 3rd) - mostly intrinsic (foetal) causes - generally can’t intervene or change prognosis

Late onset (3rd trimester) - mostly extrinsic factors - may be able to intervene to some extent, better prognosis but still associated with adverse outcomes

Question 12

How sensitive is symphyseal-fundal height at detecting IUGR?

Answer 12

detects 2/3 cases

Question 13

If IUGR clinically suspected, what are the subsequent steps in Rx?

Answer 13

1. Confirm on U/S
   - Best performed at 34W
   - Measure multiple parameters to estimate foetal weight and assess foetal wellbeing
2. Investigate for cause (if early onset, severe or suspicion for specific cause)
   - clinical hx & examination to look for maternal disease
   - FBE, U&Es, anti-phospholipid syndrome
   - karyotype and detailed U/S to look for abnormalities

Question 14

What features on U/S are used to assess growth?

Answer 14

Head (biparietal) diameter
Femur length
Abdominal circumference - most accurate

These measurements used to estimate foetal weight and percentile

Question 15

What features on U/S can be used to assess foetal well being?

Answer 15

Doppler velocity of umbilical artery

Volume of amniotic fluid

Question 16

What information can be used to assess overall foetal well-being?

Answer 16

U/S - doppler velocity, amniotic fluid volume
CTG - reassuring or non-reassuring
Foetal movements - maternal perceived normal or decreased amount or pattern

Biophysical profile - foetal movements, tone, HR, fluid volume and breathing movements - score calculated

Question 17

What are the consequences of IUGR/SGA?

Answer 17

Preterm labour

Increased perinatal mortality - stillbirth, neonatal death

Increased risk of long-term complications - ID, cerebral palsy

Increased risk of adult morbidity - diabetes, CVD

Meconium aspiration

Irritable infant, poor feeder

Question 18

What is the best Rx of confirmed IUGR?

Answer 18

Close U/S and CTG monitoring for growth trajectory and fetal well being

Timing and mode of delivery - best evidence is to induce at 37W (best risk-benefit ratio)

Management of chronic maternal disease, reversal of causes i.e. anaemia, malnutrition or avoidance of toxins (i.e. smoking, alcohol)

Treatments/prevention with aspirin, work/rest optimisation, sildenofil, hyperalimentation (increased nutrients), packed RBC and supplemental O2 have no/minimal benefit and can be harmful