Small For Dates

Question 1

broadly speaking, what might cause a small baby?

Answer 1

pre term
small for gestational age (intra-uterine growth restriction(IUGR)/fetal growth restriction (FGR)
- constitutionally small

Question 2

delivery before what week is considered term? what is mod-late, very and extreme pre-term?

Answer 2

before 37 weeks = pre term

• mod-late preterm = 32-36+6 weeks
• very preterm = 28-31+6 weeks
• extreme pre-term = 24-27+6 weeks

Question 3

baby born at what week has survival rate as full term?

Answer 3

34 weeks
(32 weeks = 95%)

Question 4

what can cause pre-term labour?

Answer 4

infection
overdistention (multiple pregnancy, polyhydramnios)
vascular cause (placental abruption)
intercurrent illness (pyelonephritis/UTI, appendicitis, pneumonia)
cervical incompetence
40% are idiopathic

Question 5

risk factors for preterm birth?

Answer 5

previous pre-term birth
multiple pregnancy
uterine anomaly
young age (teenagers)
parity
ethnicity
poor socio-economic status
smoking
drugs (esp cocaine)
low BMI

Question 6

most common causes for preterm birth?

Answer 6

planned C/section (for severe pre-eclampsia, kidney disease or poor foetal development)
premature rupture of membrane
emergency event (placental abruption, infection, eclampsia etc)
40% unknown

Question 7

definition of small for gestational age?

Answer 7

estimated fetal weight or abdominal circumference below 10th centile

Question 8

what is defined as low birth weight?

Answer 8

birth weight <2.5kg (regardless of gestation)

Question 9

what is IUGR/FGR defined as?

Answer 9

failure to achieve growth potential

Question 10

symmetrical vs asymmetrical IUGR?

Answer 10

symmetrical (infection/chromosomal abnormality) = small head and small abdomen
asymmetrical (placental abnormality) = normal head, small abdomen

Question 11

examples of risk factors for small for gestational age (SGA) pregnancy?

Answer 11

minor
- age >35 years
- IVF
- low BMI
- first pregnancy
- smoking
major
- age >40
- paternal SGA
- cocaine
- daily vigorous exercise
- chronic hypertension or complicated diabetes

Question 12

how many major/minor risk factors warrant regular monitoring of growth?

Answer 12

1 major risk factor = regular US from 26-28 weeks until 36 weeks (serial growth scans)

3 minor risk factors = growth scan at 34 weeks
- if there was an abnormal uterine artery doppler at 20 weeks then they should be monitored as if they have 1 major risk factor

Question 13

all women (regardless of risk factors) should have SFH measured from which week?

Answer 13

24 weeks
- growth scan if single measurement under 10th centile on customised chart or if serial measurements suggest slow/static growth

Question 14

how is SGA diagnosed?

Answer 14

measurement of fetal AC
combine with head circumference +/- femur length to give EFW
can use additional information (liquor volume or amniotic fluid index and dopplers)

Question 15

why are dopplers used in pregnancy?

Answer 15

provide information in the blood flow to baby through placenta
used at 20 weeks to scan uterine artery to look for a notch (showing resistance in vessel)
- resistance in uterine arteries can cause small baby

Question 16

maternal factors in SGA?

Answer 16

lifestyle (smoking, alcohol, drugs)
height and weight
age
maternal disease (e.g hypertension)

Question 17

placental factors in SGA?

Answer 17

infarcts
abruption
often secondary to hypertension

Question 18

fetal factors in SGA?

Answer 18

infection (rubella, CMV, toxoplasma)
congenital abnormalities (e.g absent kidneys)
chromosomal abnormality (e.g Down's syndrome)

Question 19

possible consequences of IUGR?

Answer 19

antenatal/in labour = risk of hypoxia and/or death
post natal
- hypoglycaemia
- asphyxia
- hypothermia
- polycythaemia
- hyperbilirubinaemia
- abnormal reurodevelopment

Question 20

clinical features of poor growth?

Answer 20

predisposing factors present
fundal height less than expected
reduced liquor
reduced fetal movements (important symptom)

Question 21

how can fetal wellbeing be assessed?

Answer 21

assessment of growth
cardiotocography
biophysical assessment
doppler US (umbilical artery - measures resistance to flow)

Question 22

biophysical profile in pregnancy?

Answer 22

US (usually combined with CTG)
considers
- movement
- tone
- fetal breathing movements
- liquor volume

then scores out of 10

• 8-10 = satisfactory
• 4-6 = repeat
• 0-2 = deliver fetus

Question 23

what do you want to see in umbilical artery doppler?

Answer 23

positive flow (even when mum is in diastole, baby is getting blood via placenta)
- wave pattern but never reaches zero

(bad if gaps seen and very bad if reversed - graph goes below zero in gaps)

Question 24

timing of delivery in SGA?

Answer 24

if all is well deliver by 37 weeks
indications for early delivery by C/section
- growth becomes static
- abnormal umbilical artery doppler
- normal umbilical artery doppler with abnormal MCA doppler between 32-37 weeks
- abnormal umbilical artery doppler with abnormal ductus venosus doppler between 24-32 weeks

Question 25

what is given if considering/planning early delivery

Answer 25

steroids (to help foetal lung maturity)
magnesium sulphate (gives some protection against cerebral palsy)