Small for Dates Flashcards
What can cause a baby to be small for its date?
- Pre term delivery
- Intra uterine growth restriction (IUGR)
- Constitutionally small
A preterm birth is before what gestational age?
- Delivery before 37 weeks
- Extreme preterm: 24 – 27+6 weeks
- Very preterm: 28 – 31+6 weeks
- Moderate to late preterm: 32 – 36+6 weeks
What is the difference in survival when babies are born very preterm?
23 weeks = 19%
Whereas
26 weeks = 77%
What conditions may cause a preterm birth?
- Infection - Pyelonephritis / UTI/ Appendicitis/ Pneumonia
- ‘Over distension’ => Multiple Preg/Polyhydramnios
- Vascular => Placental abruption
- Cervical incompetence
- Idiopathic
What factors increase the risk of a preterm birth?
- Previous pre-term labour
- Multiple
- Uterine anomalies
- Age (teenagers)
- Parity (=0 or >5)
- Ethnicity
- Poor socio-economic status
- Smoking
- Drugs (especially cocaine)
- Low BMI (<20)
What can cause a pre-term labour?
- Planned caesarean section (pre-eclampsia, kidney disease or poor fetal development)
- Premature rupture of membranes
- Emergency (placental abruption, infection, eclampsia)
- Idiopathic
What does it mean if a baby is defined as “Small for Gestational Age”?
Estimated foetal weight (EFW) or Abdominal Circumference below the 10th centile
What is meant by the terms Intra-uterine growth restriction (IUGR) and low birth weight (LBW)?
IUGR = Failure to achieve growth potential
LBW = birth weight below 2.5 kg (regardless of gestation)
Intra-uterine growth restriction can be symmetrical or asymmetrical. Explain what this means and what is most likely to cause each.
Symmetrical = all parts of baby’s body are proportionately small
- usually caused by chromosomal problem
Asymmetrical = head normal, but abdomen is small => disproportionate to each other
- usually caused by placental supply problems => foetus directs all blood to head to keep brain perfused
Give some examples of major and minor antenatal risk factors for small babies?
MAJOR
- BMI>40
- Smoking >11 cigarettes /day
- Other medical conditions - HT, Diabetes, renal disease, antiphospholipid
MINOR
- Maternal age >35 years
- IVF
- Low BMI <20
- Smoker 1-10 cigarettes/day
- Low fruit pre-pregnancy
How do we screen for small babies antenatally?
- Measurement of symphysial-fundal height from 24 weeks
- Growth scan if measurement below 10th centile on customised chart
HOw can we diagnose a baby that is small for gestational age?
- Measurement of fetal abdominal circumference
- Combine with head circumference +/- femur length to give Estimated Foetal Weight (EFW)
- liquor volume or amniotic fluid index can also be used to see if baby is producing enough fluid
How is EFW/AC Measurement standardised? WHat is seen on every womans scan to calculate this?
Scan till we can see:
- stomach gas bubble
- C shaped umbilical vein
- One rib
ALL in the same snapshot on US
What do customised charts take into account that population charts do not?
- BMI
- Parity of mother
- Ethnicity
What maternal factors can cause a baby to be Small for gestational age (SGA)?
- Lifestyle (smoking, alcohol, drugs)
- Height and weight
- Age
- Maternal disease e.g. hypertension