L5 Normal and Disordered Foetal Growth Flashcards
How are small-for-GA babies classified?
- Normal small fetuses: no structural abnormality, normal umbilical artery Doppler and liquor -> Not at risk, no special care needed
- Abnormal small fetuses: chromosomal/structural abnormalities -> specialised care and counselling
- Growth restricted fetuses: placental dysfunction, necessitating treatment and careful timing of delivery
Define ‘small for gestational age’:
- Fetus is within 10th weight percentile for its age (in weeks)
Define intrauterine growth restriction:
- Fetus is unable to achieve its genetically predetermined size
What qualifies as low birth weight?
- Less than 2500gms
- Baby could be SGA or could simply pre born prematurely
What percentage of SGA babies are considered normal vs ‘at-risk’?
- 40% healthy, 40% growth restricted
- Those that are actually healthy should not be subjected to risky protocols or risk iatrogenic prematurity
- Only the growth-restricted fetuses are at risk of potentially preventable perinatal death
How is FGR classified and what contributes to each?
- Symmetrical or asymmetrical
- Related to underlying cause of growth delay and the duration of the insult
Describe symmetrical FGR:
- Fetal head and body are proportionately small
- Fetal insult occurring during early development, impacting growth processes and cell hyperplasia
Describe asymmetrical FGR:
- Fetal brain disproportionately large compared to liver (ratio >6)
- Fetal insult during later development -> distinct growth patterns by differential impacts on axial and peripheral skeletal growth
- Potential link to brain sparing effect
What is the brain sparing effect?
- Blood flow prioritised to brain over other areas during development
- Response to placental insufficiency
What groups of risk factors exist for FGR?
- Maternal (age, height, genetics, other conditions, lifestyle etc)
- Placental and cord abnormality
- Fetal factors (often congenital)
- Infections (TORCH, malaria)
What lifestyle factors can increase risk of fetal growth restriction? (x3)
- Drug use/abuse: marijuana, opiates, cocaine, smoking, drinking, chemotherapy, and others
- Under/overnutrition
- Altitude
List some placental and cord abnormalities:
- Incorrect cord insertion
- Single umbilical artery
- Placental tumour
- Circumvillate placenta
- Defective trophoblastic invasion/placentation
- Reduced blood flow to placental bed e.g. preeclampsia
- Vascular anomalies e.g. TTTS
- Decreased functioning mass: Small placenta, abruption, placenta praevia, post term pregnancy
Give examples of infections that are risk factors for FGR:
- TORCH
- TB
- Malaria -> can invade placenta and damage its function
- Parvo virus B19
What is the underlying mechanism of IUGR?
- Insufficient gas exchange and nutrient delivery to fetus
- Often as a result of reduced capacity to carry/deliver/recieve oygen
What factors can cause placental damage?
- Smoking
- Thrombophilia
- Autoimmune diseases
What factors can reduce oxygen carrying capacity of the mother?
- Cyanotic heart disease
- Smoking
- Haemoglobinopathy
What factors can impair oxygen delivery to the fetus:
- Diabetes with vascular disease
- Hypertension
- Autoimmune conditions
Outline the thrifty phenotype hypothesis:
- Nutritional insult during critical period of gestation may permanently impact the child
- Maternal nutritional status can alter epigenetic state of fetal genome and imprint gene expression
- Examples include development of T2DM, metabolic syndromes
Why is timing so important in delivery of FGR babies?
- Increased fetal morbidity and mortality -> 10x increase in late fetal deaths among very small fetuses
List some perinatal implications of FGR:
- Stillbirth (40% non-malformed stillbirths are SGA)
- Prematurity -> nacrotizing enterocolitis, ischaemic bowel, thrombocytopenia, temperature instability, renal failure, metabolic problems
- Asphyxia
- Congenital malformations
Long-term consequences of FGR: (mother)
- Abnormalities of hypothalamic pituitary axis
- Cardiovascular disease
- Insulin resistance
- Metabolic syndrome
Long term consequences for FGR children:
- LBW associated with high cholesterol
- Associated with decresed stroke volume, abnormally globular ventricles, high BP, increased intima-media thickness
- Other: Poor physical and intellectual performance by various metrics, behavioural problems
How can aspirin improve outcomes of IUGR?
- Prevents aggregation of platelets
- Thinning of blood improves flow
- Particularly useful in cases of preeclampsia
Evidence for clinical examination of IUGR using symphysio-fundal height:
- Poor sensitivity and specificity, not particularly fallible
- Benefits from being cheap and quick, can be conducted by the midwife
- Predictive value can possibly be improved using customisation of charts (age, ethnicity, weight and parity) -> improved sensitivity to detect SGA
What aspects of fetal biometry might be measured to help diagnose SGA?
- Biparietal diameter
- Head circumference
- Abdominal circumference
- Femur length
- Estimated fetal weight
- Amniotic fluid volumes (via deepest vertical pocket)
What surveillance is typically carried out for mothers at risk of FGR?
- Serial scans
- Antenatal cardiocography (CTG)
- Amniotic fluid volume assessment
- Umbilical doppler
- Biophysical profile assessment
What test is done on FGR neonates?
- Ponderal index (relationship between height and weight) -> Low?
- If low, can indicate hypoglycaemia, hyperbilirubinemia, necrotising enterocolitis, hyperviscosity syndromes
How may FGR be prevented?
- Known to be largely unpreventabe
- Some evidence of benefit for…
- LDA and miniheparin
- Reducing smoking
- Antibiotics to prevent UTIs
- Antimalarial prophyaxis
What is the key idea in fetal surveillance in cases of FGR:
- Careful monitoring to time delivery
- Waiting until risk of in utero demise outweighs risk of delivery and prematurity
Define fetal macrosomia and LGA:
- LGA: Above 90th percentile
- Macrosomia: BW>4000g regardless of GA
How common is macrosomia?
- 9 - 10% neonates
- Geographical variation -> potential genetic and envirnomnental factors
List the key risk factors associated with macrosomia:
- Obesity
- Diabetes (GDM/T2DM)
- Postterm gestation
- Multiparity
- Stature of parents
- Advanced maternal age
- Previous macrosomic infant
- Ethicity
What are the key complications associated with fetal overgrowth?
- Maternal diabetes
- Fetal demise
- Birth trauma -> shoulder dystocia, nerve palsies
- Neonatal hypoglycaemia
What is the greatest risk factor for macrosomia?
- Maternal hyperglycaemia
- Accelerates fetal growth
- Alters body proportions
