Foetal Development and Growth (online lecture) Flashcards
What is involved in intrauterine growth?
Involves co-ordinated increase in mass of different tissues and organs.
Usually measured in terms of changes in size/weight in relation to gestation.
Also involves alteration in body composition and functional development of tissues.
What determines size at birth?
The foetal potential for growth (Individual, genetically determined)
The environmental influences upon growth (Intrauterine environment, maternal genetics)
Length of gestation (time allowed for growth)
How is foetal growth measured?
Can be assessed by palpation or symphysis-fundal height.
Ultrasound is the most reliable assessment.
What is foetal growth defined as?
Increase in mass that occurs between the end of organogenesis and birth.
What are the 2 extremes of foetal growth?
Important to recognize the 2 extremes of foetal growth:
Macrosomia
Growth restriction
What are the extremes of foetal growth associated with?
Increased perinatal risk.
What is used to define foetuses that are restricted or grow too much? What is the limitation of this approach? How are these limitations addressed?
<10th percentile for weight typically used for growth restriction
> 90 percentile for macrosomia
May fail to identify the foetus who has failed to meet its growth potential but has a normal birth weight or the foetus who is programmed to be small genetically and grown appropriately.
Due to these limitations there are a wide range of morphometric measurements used in addition to birth weight and length to identify patterns of foetal growth.
What is normal foetal growth?
Growth according to one’s individually determined growth potential.
What are some neonatal growth morphometrics used?
Ponderal index
Body mass index
Skin fold thickness
Mid-arm circumference: Abdominal circumference
What are morphometrics used for?
Symmetrically small baby: Genetic, early pregnancy insult
Asymmetrically small baby: insult late in pregnancy
How are foetal growth curves constructed?
Normative foetal growth curves constructed from ultrasound measurements are used clinically to identify abnormal intrauterine growth.
What factors does foetal growth vary with?
Ethnicity
Altitude
Socioeconomic status
Parity
Foetal gender
Multiple pregnancy
What measures are used to recognize foetal growth as it is happening?
Head circumferance
Femur length (1mm/week in first trimester)
Abdominal circumference (lots of energy stored in liver)
What is the symmetrical growth pattern?
Head, abdomen, and leg are growing at similar rates.
What is the asymmetrical growth pattern?
Head, abdomen, and leg are growing at different rates. Often caused by dysfunctional placenta
How is size observed for growth?
Foetus is repeatedly observed over time for growth.
Growth can be optimal even if it is under the normal size if it is increasing at the correct rate.
What is the difference between a constitutionally small or large baby and a pathologically small or large baby?
Constitutionally small: Happily small baby meeting its small growth potential
Pathologically small: Small foetus that wants to be bigger but is prevented from meeting its growth potential.
Constitutionally large: Happily large baby meeting its large growth potential
Pathologically large: Large foetus driven to grow faster than it wants to.
How does glucose get past the placenta?
It can diffuse passively.(gestational diabetes leads to larger baby)
What maternal factors affect foetal growth?
Maternal size (weight + height)
Uterine size
Nutritional state (calorie intake and dietary composition)
Uterine blood flow
Anaemia (little bit of anaemia is good too much anaemia is bad)
Tobacco smoking
Substance abuse: alcohol, narcotics, amphetamines.
What placental factors affect foetal growth?
Size
Microstructure: villi density, vascular density and architecture
Umbilical blood flow
Transporters and binding proteins
Nutrient utilisation
Nutrient production
Hormone synthesis
What foetal factors affect foetal growth?
Genome: Chromosome number, imprinted genes
Nutrient production
Hormones: foeto-placental steroidogenic units and foetal endocrine glands
Growth factors: growth promoting factors and growth inhibiting factors.
