Large/Small for Gestation Age

Question 1

How large counts as macrosomic?

Answer 1

≥4kg or ≥4.5kg - definition varies → 10% of pregnancies

Question 2

What tools are used to diagnose a baby as large for age antenatally?

Answer 2

• 1st = Symphysis-fundal height → >90th/95th centile for gestational age
• 2nd = Abdominal Circumference → >90th/95th centile for gestational age
• 3rd = Estimated foetal weight → >90th/95th centile for gestational age

Question 3

What are the risk factors for LGA?

Answer 3

• Gestational or DM
• High BMI
• Foetal macrosomia (>4kg in a term infant)
• Syndromes: Beckwith-Wiedemann, Simpson-Golabi-Behemel, Soto’s syndrome
• Polyhydramnios
• Multiparity
• Advanced maternal age
• Molar pregnancy

Question 4

What are the signs and symptoms of LGA?

Answer 4

• On inspection = excessive distension for gestational age
• Abdomen = increased SFH and/or increased abdominal circumference

Question 5

What are the appropriate investigations for LGA?

Answer 5

• OGTT – for gestational diabetes
• Bloods – serum βHCG
• USS – liquor volume, biometry
• Genetic testing

Question 6

What is the management of LGA?

Answer 6

• Detected at 18-21 weeks → repeat scan
• Detected at 24-36 weeks
  
  • If acceleration of growth → arrange USS for foetal biometry
    
    • If follows same path then reassure and arrange another routine scan
    • Offer OGTT (gestational diabetes)
• Detected at 36-40 weeks
  
  • If SFH is >90th centile on routine measurements → USS for foetal biometry
  • Perform OGTT (gestational diabetes)
• Need to plan delivery and discuss risk of shoulder dystocia, nerve injuries, prolonged labour → offer CS

Question 7

What are the complications of LGA?

Answer 7

• Shoulder dystocia
• Hypoglycaemia in GDM
• Respiratory distress syndrome
• Intrauterine deformations – metatarsus adductus (foot bends inwards), hip subluxation
• Increased mortality
• Perineal tear
• Molar pregnancy

Question 8

Define SGA.

Answer 8

• Derived from birth weight
  
  • A baby with abdominal circumference or estimated foetal weight ≤10th centile for GA
• 5% of pregnancies

Question 9

Define IUGR.

Answer 9

• Derived from growth rate
  
  • A baby with a reduced growth rate → baby becomes SGA
• All IUGR babies are SGA but not all SGA babies are IUGR

Question 10

What are the risk factors for SGA/IUGR?

Answer 10

Question 11

What are the appropriate investigations for SGA or suspected IUGR?

Answer 11

• If ≥1 major risk factor or ≥3 minor risk factors = reassess at 20 weeks
• At 20 weeks, if still at risk:
  
  • ≥3 minor RFs → uterine artery doppler (20-24w) → if abnormal = serial USS from 26-28w
  • ≥1 major RF → foetal size and umbilical artery doppler + serial USS from 26-28w
• Screen for congenital infections
• During 3rd trimester = PET, severe pregnancy induced hypertension, APH abruption

Question 12

What is the management of SGA/IUGR?

Answer 12

• Smoking/Alcohol/Drugs should be stopped
• Monitoring:
  
  • 1st → SFH or risk status determined at booking appointment
  • 2nd → confirm SGA with foetal biometry (20w)
  • 3rd → uterine artery doppler (20-24w)
    
    • Normal = repeat scans every 2 weeks (from 20-24w onwards)
    • Abnormal = serial growth and doppler USS scans every week (from 26-28w onwards)
• Delivery:
  
  • Delivery by 37 weeks is usually necessary → dependent on severity and gestation
    
    • Steroids should be given <36 weeks
    • Consultant-led clinics and decision-making

Question 13

What are the indications of immediate delivery?

Answer 13

• Abnormal CTG (and reduced foetal movements)
• Reversal of end-diastolic flow

Question 14

What can be used to prevent IUGR in high risk patients?

Answer 14

Low-dose aspirin

Question 15

What are the complications of SGA/IUGR?

Answer 15

• Stillbirth
• Preterm labour
• Intrapartum foetal distress
• Birth asphyxia
• Meconium aspiration
• Postnatal hypoglycaemia
• Neurodevelopmental delay if onset <26/40
• Risk T2DM and HTN in adult life
• Perinatal morbidity and mortality