Small for Date Pregnancies Flashcards
What are the causes of small babies?
Preterm delivery
Small for gestational age (SGA) = intrauterine growth restriction (IUGR), foetal growth restriction (FGR), constitutionally small
What is preterm delivery defined as?
Delivery <37 weeks gestation
What are the different categories of preterm delivery?
Extreme preterm = 24-27+6 weeks
Very preterm = 28-31+6 weeks
Moderate/late preterm = 32-36+6 weeks
How common are preterm deliveries?
6-7% of deliveries in the UK
1 in 10 pregnancies globally
What are the preterm delivery survival rates?
19% at 23 weeks
40% at 24 weeks
>95% if beyond 32 weeks
What are some aetiologies of preterm delivery?
Infection, placental abruption, or idiopathic
Pyelonephritis/UTI, appendicitis or pneumonia
Overdistension = multiple pregnancy, polyhydramnios
Cervical incompetence or idiopathic
What are the risk factors for preterm delivery?
Previous preterm labour, multiple pregnancy, uterine anomalies, teenager, parity of 0 or >5, ethnicity, poor socio-economic class, smoking, BMI <20, drugs
What are the indications for a planned preterm C-section?
Accounts for 25% of preterm births = severe pre-eclampsia, kidney disease, poor foetal development
What are some emergency events that would lead to preterm labour?
Account for 25% of preterm births = placental abruption, infection, eclampsia
What are some common causes of preterm labour?
40% due to unknown cause
20% due to premature membrane rupture
What is small for gestational age defined as?
Estimated foetal weight (EFM) or abdominal circumference below 10th centile
What are IUGR and FGR a sign of?
Failure to achieve growth potential
What are the two types of growth restriction?
Symmetrical = small head and small abdomen Asymmetrical = normal head, small abdomen
What is used to identify small for gestational age babies?
Antenatal risk factors and screening
What are some minor antenatal risk factors for SGA?
Age >=35, IVF, nulliparity, BMI <20 or 25-34.9, 1-10 cigarettes/day, previous pre-eclampsia, low fruit pre-pregnancy, pregnancy interval <6 months or >=60 months
What are some major antenatal risk factors for SGA?
Age >40, >11 cigarettes/day, parental SGA, cocaine, daily vigorous exercise, previous SGA baby, previous stillbirth, chronic hypertension, diabetes, renal impairment, antiphospholipid syndrome, low PAPP-A, BMI>35, large fibroids, foetal echogenic bowel, heavy bleeding in pregnancy
How is SGA screened for?
All women have measurement of symphysial-fundal height from 24 weeks
When would you do a growth scan for suspected SGA?
If single symphysial-fundal height below 10th centile
What would a growth chart for SGA show?
Serial measurements suggest slow/static growth
How is SGA diagnosed?
Measurement of foetal AC then combine with head circumference +/- femur length to give EFW
What additional measurements can be taken to aid diagnosis of SGA?
Liquor volume or amniotic fluid and may do Doppler
What maternal factors influence SGA?
Lifestyle = smoking, alcohol, drugs
Height, weight, age and maternal disease
When are uterine artery Dopplers performed?
All women have them performed as part of their 20 week scan
What are the placental factors that influence SGA?
Infarcts, abruption, dysfunction
What foetal factors influence SGA?
Infection = rubella, CMV, toxoplasma
Congenital anomalies and chromosomal abnormalities
What is the link between early SGA and chromosomal abnormalities?
1 in 5 babies thought to be SGA <24 weeks will have chromosomal abnormality
What does IUGR carry a risk of during labour?
Hypoxia and death
What are the postnatal consequences of IUGR?
Hypoglycaemia, effects of asphyxia, hypothermia, polycythaemia, hyperbilirubinaemia, abnormal neurodevelopment
What are the clinical features of poor growth?
Predisposing factors, fundal height less than expected, reduced liquor, reduced foetal movements
How is foetal wellbeing assessed?
Growth scans with Doppler assessment, CTG, biophysical assessment
What is a biophysical assessment?
US combined with CTG = considers movement, tone, foetal breathing movements and liquor volume
How is a biophysical assessment scored?
Out of 10 = score of 8-10 is satisfactory, repeat if score is 4-6, deliver if score 0-2
What is the primary tool for monitoring foetal wellbeing?
Umbilical artery Doppler = uses US to give measurement of placental resistance to flow
What does the results of an umbilical artery Doppler mean?
Normal = constant flow to baby (even in diastole)
Developing resistance = absent diastolic flow, flow may eventually reverse (foetus not getting nutrition)
What are some additional Dopplers that may be done to assess foetal wellbeing?
MCA and ductus venosus Dopplers
When would you deliver a SGA?
37 weeks irrespective of growth trajectory (as long as everything is well)
What are the indications for an early C-section to deliver a SGA baby?
Growth becomes static
Abnormal umbilical artery Doppler
Normal UA Doppler with abnormal MCA between 32-37 weeks
Abnormal UA Doppler with abnormal ductus venosus Doppler between 24-32 weeks
What is the timing of delivery for a SGA baby a balance of>
The risks of prematurity and the potential hypoxia in utero or stillbirth
What centiles on a growth chart would indicate a constitutionally small baby?
babies between the 3rd and 10th centiles
What are the causes of symmetrical IUGR?
Congenital, chromosomal, intra-uterine infection, environmental
What are the causes of asymmetrical IUGR?
Pre-eclampsia, placental abruption, smoking
What does it suggest if the ductus venosus Doppler is pulsatile or has high resistance?
May suggest baby is becoming acidotic
Why does the middle cerebral artery decrease its resistance?
To maintain blood flow to the foetal brain
