[31] Small for Gestational Age Flashcards
What is meant by small for gestational age (SGA)?
An infant with a birth weight <10th centile for its gestational age
What is severe SGA?
Birth weight <3rd centile
What is fetal SGA?
An EFW or abdominal circumference <10th centile
What is severe fetal SGA?
EFW or AC <3rd centile
What is fetal growth restriction?
When a pathological process has restricted genetic growth potential
How can fetal growth restriction present?
Fetal compromise, including reduced liquor volume or abnormal Doppler studies
What is low birth weight?
An infant born with birth weight <2500g
What can the pathophysiology of SGA be divided into?
- Constitutionally small
- Placenta mediated growth restriction
- Non-placenta mediated growth restriction
What % of SGA foetuses/infants are constitutionally small?
50-70%
How are constitutionally small foetuses identified?
Small size at all stages, but growth following the centiles
What is the pathology in constitutionally small foetuses?
No pathology is present
What are the contributing factors for constitutionally small foetuses?
- Ethnicity
- Sex
- Parental height
How is placental mediated growth restriction identified?
Growth is normal initially, but slows in utero
What are the maternal factors that can result in placental insufficiency?
- Low pre-pregnancy weight
- Substance abuse
- Autoimmune disease
- Renal disease
- Diabetes
- Chronic hypertension
What can cause non-placenta mediated growth restriction?
- Chromosomal or structural abnormality
- Error in metabolism
- Fetal infection
When should women be assessed for risk factors for SGA?
At booking, and again in 20 weeks
What are the major risk factors for SGA?
- Maternal age >40
- Smoker 11 or more per day
- Previous SGA baby
- Maternal/paternal SGA
- Previous stillbirth
- Cocaine use
- Daily vigorous exercise
- Maternal disease
- Heavy bleeding
- Low PAPP-A
What maternal disease is a risk factor for SGA?
- Chronic hypertension
- Renal impairment
- Diabetes with vascular disease
- Anti-phospholipid syndrome
What is PAPP-A?
Pregnancy associated plasma protein
What are the minor risk factors for SGA?
- Maternal age 35 or over
- Smoker 1-10/day
- Nulliparity
- BMI <20 or 25-34.9
- IVF singleton
- Previous pre-eclampsia
- Pregnancy interval <6 or >60 months
- Low fruit intake pre-pregnancy
What is the role of ultrasound in SGA?
It is used for the diagnosis and surveillance of a SGA fetus
What ultrasound biometrics can be used in the assessment of fetal size?
- EFW
- AC
What is done with ultrasound biometrics to help determine fetal growth?
They are plotted on customised centile charts
What do customised centile charts take into account?
- Maternal characteristics
- Gestational age
- Sex
What maternal characteristics are taken into account on customised centile charts?
- Height
- Weight
- Ethnicity
- Parity
What ratio is important when assessing SGA?
Head circumference to AC
Why is the head circumference to AC ratio important in SGA?
A symmetrically small fetus is more likely to be constitutionally small, whereas an asymmetrically small fetus is more likely to be caused by placental insufficiency
What other ultrasound finding might be present in placental insufficiency?
Reduced amniotic fluid volume
Why might there be a reduced amniotic fluid volume with placental insufficiency?
Placental insufficiency can result in impaired kidney function, which can cause reduced amniotic fluid volume
What investigations may be appropriate in SGA?
- Detailed fetal anatomical survey
- Uterine artery Doppler
- Karyotyping
- Screening for infections
What infections should be screened for in SGA?
- CMV
- Toxoplasmosis
- Syphilis
- Malaria
How can SGA be prevented?
- Modification of risk factors
- Anti-platelet agents
Give 2 examples of how risk factors can be modified to prevent SGA?
- Promoting smoking cessation
- Optimising maternal disease
In whom might anti-platelet agents be effective at preventing SGA?
Women at high risk of pre-eclampsia
When should anti-platelet agents be started in women at high risk of pre-eclampsia?
On or before 16 weeks of pregnancy
What is the primary surveillance tool in a SGA fetus?
Uterine artery doppler
What should be done if the uterine artery doppler is normal in a SGA fetus?
Repeat every 14 days
What should be done if the uterine artery doppler is abnormal in SGA fetus?
Repeat more frequently, or consider delivery
What other tests may be useful in the surveillance of a SGA fetus?
- Symphysis fundal height (SFH)
- Middle cerebral artery (MCA) Doppler
- Ductus venosus doppler
- Cardiotocography
- Amniotic fluid volume
What should be given in SGA if delivery is being considered between 24 and 35+6 weeks gestation?
A single course of antenatal steroids
What should be done if the fetus is <37 weeks and there is absent/reverse end-diastolic flow on Doppler?
Offer C-section
What should be done if the fetus is SGA and 37 weeks?
Offer induction
What is induction for SGA fetus associated with?
High rate of C-section
What is required when inducing someone for SGA fetus?
Continuous fetal heart rate monitoring from onset of contractions
What are the neonatal complications of SGA?
- Birth asphyxia
- Meconium aspiration
- Hypothermia
- Hypo or hyperglycamia
- Polycythaemia
- Retinopathy of prematurity
- Persistent pulmonary hypertension
- Pulmonary haemorrhage
- Necrotising enterocolitis
What are the long-term complications of SGA?
- Cerebral palsy
- Type 2 diabetes
- Obesity
- Hypertension
- Precocious puberty
- Behavioural problems
- Depression
- Alzheimer’s
- Cancer
What cancers are more common in people that were SGA at birth?
- Breast
- Ovarian
- Colon
- Lung
- Blood
