Small for Dates Flashcards
Causes of small babies
Pre-term delivery
Small for gestational age
- intrauterine growth restriction/foetal growth restriction
- constituitionally small
what is a pre-term delivery
Delivery before 37 weeks gestation
extreme =24-27+6
Very preterm = 28-31+6
mod-late preterm= 32-36+6 weeks
survival rates for pre-term babies
23 weeks - 19%
24 weeks - 40%
25 weeks - 66%
26 weeks - 77%
> 32 weeks - >95%
reasons for pre-term birth
Infection
Over distension
- multiple pregnancy
- polyhydramnios
Vascular
-placental abruption
Intercurrent illness
- pyelonephritis
- appendicitis
- pneumonia
Cervical incompetence
Idiopathic
Pre-term birth risk factors
Previous preterm labour Multiple pregnancy Uterine anomalies Age (teenagers) Parity (0 or >5) Ethnicity Poor socioeconomic status Smoking Drugs (cocaine) Low BMI <20
how are pre-term babies normally delivered
25% planned Caesarean
20% premature rupture of membranes
25% Emergency event
40% cause unknown
what is a small for gestational age foetus
Estimated foetal weight or abdominal circumference below the 10th gentile
low birth weight = birth weight below 2.5kg
what is an intrauterine growth restriction
failure to achieve growth potential
can be symmetrical (small head and small body)
or asymmetrical (small body normal head)
what does symmetrical growth restriction suggest
chromosomal abnormality
in utero infection
what does asymmetrical growth restriction suggest
placental cause for restriction
major risk factors for small for gestational age babies
Maternal age >40 Smoker >11 cigarets/day Paternal SGA Cocaine use Daily vigorous exercise Previous SGA baby Previous still birth Maternal SGA Chronic hypertension Diabetes with vascular disease Renal impairment Antiphospholipid syndrome Heavy bleeding in pregnancy Low Papp-A Foetal echogenic bowel BMI>35 Known large fibroids
how do you screen for small for gestational age babies
Symphysial-funcdal height
if single measurement below 10th gentile go for a growth scan
how do you diagnose SGA
measurement of fetal abdominal circumference
combine with head circumference +/- femur length to give estimated foetal weight
Causes of a baby being small for gestational age
Maternal factors
Placental factors
Fetal factors
maternal factors for small for gestational age
Smoking Alcohol Drugs Height and weight Age Maternal disease eg. hypertension
why do women get uterine artery dopplers as part of their 10 week scan
uterine arteries should be low resistance in the 2nd trimester
if they are found to have resistance the baby is at risk of SGA and hypertensive disease in pregnancy
most likely due to abnormal placentation
placental factors for SGA
Infarcts
Abruption
Secondary to hypertension
foetal factors for SGA
Infection eg. rubella, CMV, toxoplasma
Congenital anomalies eg. absent kidneys
Chromosomal abnormalities eg. downs syndrome
what are the consequences of intrauterine growth restriction
Antenatal/in labour - risk of hypoxia or death
Post natal - hypoglycaemia asphyxia (hypoxia) hypothermia polycythaemia hyperbilirubinaemia abnormal neurodevelopment
how do SGA babies usually present
Predisposing factors
Small fundal height
Reduced liquor
Reduced foetal movements
how do you asses fetal wellbeing
assessment of growth
cardiotocography
biophysical assessment
doppler ultrasound
what is a biophysical profile
ultrasound assessment of the baby
considers:
- movement
- tone
- fetal breathing movements
- liquor volume
score out of 10
8-10 satisfactory
4-6 repeat
0-2 deliver
what is an umbilical artery doppler
uses ultrasound
measures placental resistance to flow
normal = constant flow of blood to baby even in diastole
when do you deliver an SGA baby
if all well, deliver by 37 weeks
early delivery by Caesarian if:
- growth becomes status
- abnormal umbilical artery doppler
- normal umbilical artery doppler with abnormal MCA between 32 and 37 weeks
- abnormal umbilical artery doppler with abnormal ductus venous doppler between 24-32 weeks
why would you give steroids in an early delivery
to promote foetal lung maturity and avoid foetal respiratory distress syndrome
usually if baby is <36 weeks
why do you give magnesium sulphate in an early delivery
some fetal neuroprotection against cerebral palsy if delivery is planned <32 weeks
