3.5 Abnormal Foetal Growth

Question 1

Define SGA (small for gestational age)
Define LGA

Answer 1

EFW or AC <10th centile => 10% of population is SGA
LGA is >4.5kg or >90th centile => 20% of population is wither SGA or LGA
Severe would be <5 or >95

Question 2

Give 2 methods of determining SGA or LGA

Answer 2

SFH or US measurment of AC, HC, BP diameter, and femur length

Question 3

66% of those SGA are due to physiological causes such as small parental size and/or ethnicity. Give 5 non-physiological causes that you might get a low SFH on exam

Answer 3

Maternal:
1) Congenital infection
2) HTN/Pre-eclampsia
3) DM/GDM
4) Smoking/drugs
5) Medications

Foetal:
1) Multiple pregnancy
2) Fetal chromosomal abnormalities
3) An/oligohydramnios
4) Chromosomal abnormalities/short-stature

Others (dont count): Incorrect measurement

Question 4

State the causes of small SFH on exam

Answer 4

1) ROM
2) IUGR => Placental Insufficiency
Maternal:
1) Congenital infection
2) HTN/Pre-eclampsia
3) DM/GDM
4) APS, SLE
5) Smoking/drugs
6) Medications

Foetal:
1) Multiple pregnancy
2) Fetal chromosomal abnormalities
3) An/oligohydramnios
4) Chromosomal abnormalities/short-stature

3) Congenital renal anomalies (hydronephrosis, congenital agenesis)

Question 5

What causes of SGA are symmetrical? Which are asymmetrical

Answer 5

Symmetric is due to infection or chromosomal abnormalities as well as environmental (drug smoking) + antiepilectic meds that would later lead to oligohydramnios. Also, being constitutionally small is symmetrical

Asymmetric is typically due to utero-placental insufficiency due to brain-sparing effect=> HTN/Pre-eclampsia

Question 6

What are the implications for non-physiologically SGA?

Answer 6

Fetus: Foetal hypoxia

Neonates:
Hyperbilirubinemia/ jaundice
Hypoglycemia
Meconium aspiration
Necrotising enterocolitis!!!
Polycythemia

Infant:
Short stature
Delayed neurological development
Cerebral Palsy!!

Adult: increased risk of
CVD
DM

Question 7

When would you aim to deliver a foetus that is SGA?

Answer 7

37 weeks

Question 8

How would you manage (not just treat) a mother presenting with a reduced SFH for her GA

Answer 8

1) Chromosomal defects: NIPT and amniocentesis for karyotyping
2) Optimize RF: Cessation of smoking/drug use, medication adherence for GDM, HTN
3) TORCH screen
4) Monitor foetal wellbeing (CTG, US doppler…)
5) Steroids if delivery likely <35 weeks
6) Delivery by 37 weeks via C-section

Question 9

When are steroids indicated?
Give 2 examples
how is it administered?
List 3 fetal benefits
List 1 maternal risk

Answer 9

If delivery expected <35 weeks => from viability until 34+6 weeks
Examples: Dexamethasone/Betamethasone (care for reduced variability with this one)
Administration: 2 IM injections 12mg, 12 hours apart

Fetal benefits: Increased surfactant => lung maturity => reduced risk of RDS, reduced risk of NEC, and reduced risk of IVH (intraventricular hemorrhage)

Maternal risks: Hyperglycemia and poor sleep

Question 10

You are examining a patient at 38 weeks gestation with an SFH of 42. What is your ddx

Answer 10

Constitutionally large
Polyhydramnios
Post-term pregnancy
Maternal obesity
Multiple gestation
Hx of big babies
Incorrect measurement by examiner

Question 11

What are the risks of macrosomia. Give 5 risks

Answer 11

Prolonged 2nd stage of labour
increased risk of conversion to emergency C-section
Increased risk of perineal tears
Increased risk of operative delivery
Increased risk of PPH
Increased risk of shoulder dystocia

Question 12

When would you deliver a baby that is LGA?
How would you deliver the baby?

Answer 12

39 weeks GA
If > 5kg -> C-section unless Diabetic => 4.5kg