Small For Dates Flashcards
broadly speaking, what might cause a small baby?
pre term
small for gestational age (intra-uterine growth restriction(IUGR)/fetal growth restriction (FGR)
- constitutionally small
delivery before what week is considered term? what is mod-late, very and extreme pre-term?
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
baby born at what week has survival rate as full term?
34 weeks (32 weeks = 95%)
what can cause pre-term labour?
infection
overdistention (multiple pregnancy, polyhydramnios)
vascular cause (placental abruption)
intercurrent illness (pyelonephritis/UTI, appendicitis, pneumonia)
cervical incompetence
40% are idiopathic
risk factors for preterm birth?
previous pre-term birth multiple pregnancy uterine anomaly young age (teenagers) parity ethnicity poor socio-economic status smoking drugs (esp cocaine) low BMI
most common causes for preterm birth?
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
definition of small for gestational age?
estimated fetal weight or abdominal circumference below 10th centile
what is defined as low birth weight?
birth weight <2.5kg (regardless of gestation)
what is IUGR/FGR defined as?
failure to achieve growth potential
symmetrical vs asymmetrical IUGR?
symmetrical (infection/chromosomal abnormality) = small head and small abdomen
asymmetrical (placental abnormality) = normal head, small abdomen
examples of risk factors for small for gestational age (SGA) pregnancy?
minor - age >35 years - IVF - low BMI - first pregnancy - smoking major - age >40 - paternal SGA - cocaine - daily vigorous exercise - chronic hypertension or complicated diabetes
how many major/minor risk factors warrant regular monitoring of growth?
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
all women (regardless of risk factors) should have SFH measured from which week?
24 weeks
- growth scan if single measurement under 10th centile on customised chart or if serial measurements suggest slow/static growth
how is SGA diagnosed?
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)
why are dopplers used in pregnancy?
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
maternal factors in SGA?
lifestyle (smoking, alcohol, drugs)
height and weight
age
maternal disease (e.g hypertension)
placental factors in SGA?
infarcts
abruption
often secondary to hypertension
fetal factors in SGA?
infection (rubella, CMV, toxoplasma) congenital abnormalities (e.g absent kidneys) chromosomal abnormality (e.g Down's syndrome)
possible consequences of IUGR?
antenatal/in labour = risk of hypoxia and/or death post natal - hypoglycaemia - asphyxia - hypothermia - polycythaemia - hyperbilirubinaemia - abnormal reurodevelopment
clinical features of poor growth?
predisposing factors present
fundal height less than expected
reduced liquor
reduced fetal movements (important symptom)
how can fetal wellbeing be assessed?
assessment of growth
cardiotocography
biophysical assessment
doppler US (umbilical artery - measures resistance to flow)
biophysical profile in pregnancy?
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
what do you want to see in umbilical artery doppler?
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)
timing of delivery in SGA?
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
what is given if considering/planning early delivery
steroids (to help foetal lung maturity) magnesium sulphate (gives some protection against cerebral palsy)
