Lecture 14: Fetal growth Flashcards
What is low birthweight?
<2500g
What is low birthweight associated with?
- x6 fold increase in perinatal mortality and morbidity
- Increased inattention, hyperactivity and behavioural problems
- Decreased postnatal growth
- Lower income
- Increased adult non-communicable disease i.e metabolic syndrome
What is high birthweight?
> 4500g
What is associated with high birthweight?
- Birth trauma
- Increased neonatal admissions
- Increased childhood obesity
- Increased adult non-communicable diseases
- > Metabolic syndrome
- > Depends on body composition
What are key risk factors for high birthweight?
Maternal obesity and gestational diabetes
How does the environment in early life play into development?
Obesinogenic and under-nutrition environment environment can lead to CV disease or metabolic syndrome if theres a mismatch between in-utero environment and external.
What are the determinates of fetal growth?
- Substrate supply (placenta) -> Nutrition
- Fetal Hormones
- Genetics
How does the maternal environment constrain growth?
Maternal constraint:
- maternal body habitus (tall v short, fat v slim)
- Multiple pregnancies
- First born child
- Adolescent mother
Describe the fetal supply line:
Insert slide 12
How does the placental transport glucose and what is their role?
Facilitated diffusion (GLUT 1)
Key oxidative fuel (~80% energy)
Limited fetal gluconeogenesis
Carbon source for tissue accretion
How does the placental transport amino acids and what is their role?
- Active transport
- Placenta synthesis
- Fetoplacental shuttle
Key role in metabolic balance between oxidation vs growth
Carbon and nitrogen for tissue accretion, nucleotides (DNA)
What are the fetal growth hormones?
IG1, IG2 and Insulin are mjr players
Growth hormones Thyroid hormones Corticosteroids Sex hormones Placental lactogen Prolactin Catecholamines
What regulates IGF1?
IGF-1 is regulated by fetal nutrition
AA have little impact, glucose is main substrate in this regulation
What does insulin stimulate in the fetus and how do they act together?
Insulin stimulates IGF-1
IGF-1 and insulin act together to match fetal growth to nutrition
What are the actions of insulin in the fetus?
Main actions:
- Tissue accretion
- Fuel storage
- > Increases glucose uptake
- > Fat deposition
- > Protein anabolism
- > Placental growth
What is the implication of maternal diabetes?
-> Increased glucose crossing the placenta and thus blood glucose of fetus
= Increased substrate and increased fetal insulin
= Excess fetal growth and fuel storage i.e fetal macrosomia
How does genetics impact fetal growth?
- Ethnicity and fetal sex account for 20% variance in birthweight
- Genetic factors have more influence on lean mass
- Fetal growth is normally limited by constraint
i. e Non-genetic / non-pathological factors that limit fetal growth
What is maternal constraint and how does it impact fetal growth?
- Major constraining factor is the ability of the utero-placental unit to supply oxygen and nutrients
What are maternal constraint factors?
- Maternal size (predictor of birth weight)
- Maternal age - adolescent pregnancy
- Parity - primiparous
- Short inter-pregnancy interval
- Macronutrient imbalance
What can causes constraint during embryogenesis?
- Twins even if removed reduces size
- Periconceptual undernutrition alters fetal growth trajectory
Fetal growth is normally constrained below optimal for survival
What determines fetal growth?
Fetal growth is normally constrained by the maternal environment
If endocrine status is adequate, growth is normally regulated by substrate supply
What determines post natal growth?
- Is normally to genetic potential
- If nutritional status is adequate, growth is normally regulated by endocrine status
What is the best birth size terminology?
Weight for gestation
Appropriate for gestational age (10-90th centile)
SGA (<10%)
LGA (>90%)
What is fetal growth restriction?
- In utero growth potential limited by pathological process
- Decreased accretion of fat > lean tissue +/- skeletal growth
- Causes: Fetal undernutrition and fetal pathology
