SGA/LGA Flashcards
Define Small for gestational age (SGA) and what defines severe SGA
infant with a estimated foetal weight (EFW) or abdominal circumference (AC) <10th centile, birth weight <10th centile for its gestation
Severe = EFW or AC <3rd centile
Define low birth weight
Infant with birth weight <2500g
Define Intrauterine growth restriction
foetuses that have failed to reach their growth potential due to pathological restriction
What are the types of SGA
Symmetrical (proportional): All growth parameters are symmetrically small and equally reduced. Suggests a prolonged period of poor IU growth starting in early pregnancy (or gestational age is incorrect)
Asymmetrical (disproportional): The weight or abdominal circumference lies on a lower centile than that of length and head circumference
This occurs when the placenta fails to provide adequate nutrition late in pregnancy, but brain growth is relatively spared at the expense of liver glycogen and skin fat.
What are the causes of SGA babies
Constitutional determinants:
- Low maternal height and weight
- Nulliparity
- Asian ethnic group
- Female foetus
Pathological
Maternal: pre-existing disease, pregnancy complications (PET), smoking, drugs (Cocaine), infection, extreme exercise, malnutrition
Placental (insufficiency): inadequate trophoblastic invasion, PET, autoimmune disease, multiple gestation, infarction, abruption
Foetal: congenital abnormalities e.g. chromosomal, inborn errors of metabolism, infections, structural abnormalities
What are the minor risk factors for having a SGA baby
Maternal age >35
IVF singleton pregnancy
Nulliparity
BMI <20 or >25
Smoking 1-10 cigarettes per day
Previous PET
Pregnancy interval <6 months or >60 months
What are the major risk factors for having a SGA baby
Maternal age >40yo
Lifestyle: BMI <20 or >25, Smoking >11 cigarettes per day, Cocaine use, Daily vigorous exercise
Previous: SGA baby, stillbirth
Maternal or paternal SGA
Maternal: Chronic hypertension, Diabetes, Renal impairment, Antiphospholipid syndrome
What is the management for a small SFH (<10th centile, >2cm less than expected), 3 minor RFs or 1 major RF
Reassess at 20 weeks: foetal biometry (biparietal diameter, head circumference, abdominal circumference and femur length)
What is the management for a baby who is SGA on the 20 week scan
Minor risk → uterine artery doppler (20-24w)
- Normal: US and uterine artery doppler every 2 weeks
Major risk → foetal size + umbilical artery doppler + serial US from 26-28w
+ repeat anomaly scan
+ serology for infection
+ chromosomal abnormality testing: amniocentesis, karyotyping
→ at 34w, start adding middle cerebral artery (MCA)→ cerebroplacental ratio (CPR)
What is the management if the uterine artery doppler from 20-24w is abnormal
Serial US growth scans every week
Umbilical artery doppler US scans twice a week
- Twice a week- if end diastolic velocities are normal
- Daily- absent/ reversed end-diastolic frequencies
Delivery indicated by 36 weeks, consider ELCS
What are the delivery indications for SGA babies
Immediate delivery:
Abnormal CTG and reduced foetal movements
Absent/reversed end-diastolic flow (AREDV)
>37 weeks (abnormal doppler)
Delivery should ideally be done for 37 weeks, but may be <32 if the above are present
What considerations should be made for SGA babies in delivery
Consultant-led
Immediately precede with magnesium sulphate + steroids if <34w
37 weeks → induction of C-section
Severely preterm:
>32w: delivery by c-section
<32w: daily CTG or ductus venosus doppler, delivery by C-section if abnormal
What are the complications of SGA
Stillbirth
PTL
Intrapartum foetal distress
Birth asphyxia
Meconium aspiration
Postnatal hypoglycaemia
Reduced growth in femur length and abdominal circumference
Neurodevelopmental delay
Risk T2DM and HTN in adult life (asymmetrical)
What is the prognosis for SGA
90% of SGA babies catch up in the first 2 years
Normal constitutionally SGA babies have good prognosis
increased perinatal morbidity and mortality
increased neurodevelopmental delay if onset <26/40
Define LGA and macrosomia
Large for gestational age = neonatal birth weight >90th percentile
SFH >90th/95th centile for gestational age
Abdominal Circumference (AC) >90th/95th centile for gestational age
Estimated foetal weight (EFW) >90th/95th centile for gestational age
macrosomia = >4kg or >4.5kg,
