Foetal Growth Flashcards
Define foetal growth
The increase in mass that occurs between the end of the embryonic period and birth
How do you determine external size?
via. Symphysis Fundal Height (SFH)
Distance between pubic symphysis & fundus of uterus
Why might you get errors in size due to it being LOWER than they should be?
- Wrong LMP date
- Baby in a transverse line
- Complications including oligohydramnios (low levels of amniotic fluid levels)
- Baby that is small for GA (SGA)
Why might you get errors in size due to it being GREATER than they should be?
- Wrong LMP date
- Multiple pregnancy
- Maternal obesity
What complications could arise due to the external measurement of size via. SFH?
- Molar pregnancy
- Fibroids
- Polyhydraminos
- Baby that is large for GA (LGA)
Issue with historical data on foetal size and growth and what’s it been replaced with?
Bases on miscarriages
• did NOT take into account the causative relationship betw. the LOW FOETAL GROWTH leading to miscarriages
HENCE replaced by UTERO SCANNING DATA
2 main factors important for foetal growth?
- Genetic potential
• derived from parents - Substrate supply
• sufficient nutrients essential to achieve genetic potential
What can Ultrasound Scanning (US) be used to idenfity?
- Bipartietal Diameter (BPD)
- Head Circumference (HC)
- Abdominal Circumference (AC)
- Femur Length (FL)
ALL OF THESE COMBINE TO GIVE:
Estimated Foetal Weight (EFW)
What is US used mainly to assess?
OVERALL foetal well-being
i.e. chromosomal abnormalities
What can be obtained from each of the US measurements?
Normative growth curves
Due to differences in people, customised foetal growth charts may be used
• based on foeta weight curves for normal pregnancies
• Adjusted to reflect maternal constitutional variation (i.e. mother weight)
• Optimised (w. curves free from data influences by pathological influences)
Overall average rate at which an infant gains weight?
o 14-15 weeks
• 5g/day
o 20 weeks
• 10g/day
o 32-34 weeks
• 30-35g/day
o >34 weeks
• velocity decreases
Fastest velocity is mid-third trimester
Normal foetal growth is characterised by 3 main phases…..
Cellular Hyperplasia
• 4-20 weeks
Hyperplasia & Hypertrophy
• 20-28 weeks
Hypertrophy dominates
• 28-40 weeks
• hence why mid-3rd trimester is the GREATEST growth velocity
Issues with dating the pregnancy?
Hard to date due to issues such as LMP date
BUT important to get it right to classify GA
Best practice to date pregnancy?
Ultrasound
Determine the CROWN-RUMP LENGTH of foetus
• end of 1st trimester
• variations in foetal size are MORE LIMITED at this stage so more accurate date
2 types of factors affecting foetal growth?
- Maternal factors
2. Feto-placental factors
What are some Maternal Factors influencing foetal growht?
Poverty
– more likely to be young (low birth weight) and be less educated on risks
Mother’s age
– too young or too old can impact baby health
Drug use and alcohol
• e.g. lead to FAS (foetal alcohol syndrome)
Smoking and nicotine
Diseases
Mother’s diet and physical health
– MALNUTRITION is the most important factor in baby growth
Mother’s prenatal depression
Environmental toxins
What are some Feto-placental factors affecting foetal growth?
Different genotypes
Gender
– males tend to be bigger than females
Previous pregnancy
– infants are heavier in the 2nd and subsequent pregnancies.
Hormones
– one important hormone is IGF-1 that acts to:
• Increase mitotic drive
• Increase nutrient availability for tissue accretion
o Little effect on tissue differentiation (this is mediated by cortisol)
Define SGA IUGR LBW VLBW ELBW
SGA
• Small for GA
• birth weight <10th centile
IUGR
• failure of infant to achieve its predetermined (genetic) potential for a variety of reasons
LBW
• Low Birth-Weight
VLBW
• Very LBW
ELBW
LAST 3 do NOT take GA into account
• simply refer to infants weight at delivery
Why is it important that the last 3 definitions do NOT take GA into account?
Important to determine between pre-term babies that are of a:
• LBW
and those that are
• IUGR (greater risk)
Explain how the growth axis can be used to capture babies that are IUGR
Age on x-axis and weight on y-axis
The 10th centile is most sensitive and the 3rd centile is most specific
• 10th centile will capture all babies with IUGR but also those that are SGA
i.e. captures false +ve
• 3rd centile captures IUGR but also misses some
• No consideration of genetics
When is IUGR used and outcomes of it?
IUGR is only used for DEFINITE evidence that growth has altered
- Most common cause of still-born babies
- Have increased incidence of complications (medlearn!)
- Subsequent pregnancies may also be affected
Causes of IUGR?
Generally, develops in the 2nd and 3rd trimesters
• as the 1st stage focuses on embryology (up to 50g weight)
Divided into 4 categories:
Maternal medical factors – infection, pre-eclampsia, uterine abnormalities, etc.
Maternal behavioural factors – i.e. alcohol.
Foetal factors – i.e. multiple pregnancy.
Placental factors – i.e. placental cysts, impaired trophoblast invasion
What is Pre-eclampsia
Hypertension
&
Proteinuria
• (protein in the urine)
Link between IUGR and pre-eclampsia?
There is a CLOSE LINK between IURG and pre-eclampsia
Due to main cause of pre-eclampsia is diminished remodelling of spiral arteries by cytotrophoblasts
• this causes decreased blood flow and hence decreased nutrient supply to the placenta and foetus
Management of IUGR and pre-eclamptic pregnancies?
Corticosteroids should be administered
• at gestations <36 weeks
•to improve neonetal wellbeing, particuarly the LUNGS
For pre-eclampsia
• DELIVERY is best treatment as placenta is the 1o cause
