Fetal growth Flashcards
What is the definition of fetal growth?
Increase in mass that occurs between the end of embryonic period and birth
What does fetal growth depend on?
Genetic potential
Substrate supply
What are the 3 phases of normal fetal growth?
Cellular hyperplasia
Hyperplasia and hypertrophy
Hypertrophy alone
What is the pattern of fetal growth?
14-15 wks: 5g /day
20 wks: 10 g/day
32-34 wks: 30-35g/day
> 34 wks: growth rate decreases
What techniques can be used for assessing fetal growth?
Symphysis fundal height (SFH)
Ultrasound crown-rump length - the gold standard
Note:
It should be done towards the end of the 1st trimester as fetal growth is less varied then
What’s the technique of SFH?
distance over the abdominal wall from the symphysis to the top of the uterus
What are the pros and cons of SFH?
Pros:
Simple
Inexpensive
Cons:
Low detection rate: 50-86%
Great inter-operator variability
Influenced by a number of factors (BMI, fetal lie, amniotic fluid, fibroids)
How is fetal growth assessed by ultrasound?
Biparietal diameter (BPD), Head circumference (HC) Abdominal circumference (AC) Femur length (FL) and their combination (EFW)
What is the use of ultrasound assessment of fetal growth?
Assessment of fetal “wellness” not just size
Looking at trends in growth from centile graphs
Predicting fetal metabolic compromise
Anticipating the need to deliver prematurely
What are the maternal factors influencing fetal growth?
Poverty: younger mothers and less education
Age: 16-35 is best
Drug use: developmental defects, still births, premature delivery, LBW, addiction
Weight
Disease:
hypertension
diabetes
coagulopathy
Smoking and nicotine
Alcohol: brain development
Diet
Prenatal depression
Environmental toxins
What are the feto-placental factors influencing fetal growth?
Genotype – genetic potential
Gender (B>G)
Hormones
Previous pregnancy - 2nd child likley to be bigger than the 1st
What are the 3 features of a customised growth chart?
Adjusted to reflect maternal constitutional variation maternal ht, wt, ethnicity, parity
Optimised by presenting a standard free from pathological factors such as diabetes and smoking
Based on fetal weight curves derived from normal pregnancies
What can a small SFH indicate?
wrong dates
small for gestational age
oligohydramnios
What can a large SFH indicate?
wrong dates
molar pregnancy
multiple gestation
large for gestational age
Polyhydramnios
Maternal obesity
Fibroids
What is the definition of low birth weight, very low birth weight and extremely low birth weight??
LBW = Less than 2,500g at delivery. VLBW = Less than 1,500g at delivery. ELBW = Less than 1,000g at delivery.
What are centile charts useful for?
Plotting serial measurements to monitor that the baby is growing consistently along the same centile
Why is data on fetal weight throughout pregnancy potentially wrong?
Data is collected from miscarriages, so there is potential for them to have a low birth weight.
Why is correct dating important?
It can determine whether the baby is judged to be low or high weight for its age
This effects decisions like whether to have a cesarian section or whether to try and resuscitate a pre term baby
What is the definition of Intrauterine growth restriction (IUGR)
Failure of the infant to achieve its predetermined (genetic) potential for a variety of reasons
What is the definition of Small for gestational age (SGA)?
The infant has a birth weight <10th centile (also called ‘Small for dates’).
Why is it important to distinguish between LBW and IUGR?
LBW may simply be LBW because they were pre-term
IUGR has increased risk of morbidity and mortality
How should IUGR be defined?
The term IUGR should only be used for fetuses with definite evidence that growth has altered.
The serial measurements should show that the infant is not growing ‘along a centile’, but is growing less than would be expected.
When does IUGR develop?
In the 2nd and 3rd trimesters when growth is fastest
What are the short term consequences of IURG?
Respiratory distress Intraventricular haemorrhage Sepsis Hypoglycaemia Necrotising enterocolitis Jaundice Electrolyte imbalance
What are the medium term consequences of IURG?
Respiratory problems
Developmental delay
Special needs schooling
What are the long term consequences of IURG?
Fetal programming
What is fetal programming?
A number of organ structures and associated functions undergo programming during embryonic and fetal life
This determines the set point of physiological and metabolic responses that carry into adulthood.
Hence, any stimulus or insult at a critical period of embryonic and fetal development can result in developmental adaptations that produce permanent structural, physiological and metabolic changes.
Thereby predisposing an individual to cardiovascular, metabolic and endocrine disease in adult life
What is strongly associated with IUGR? Explain this link
Pre-eclampsia
The main cause of pre-eclampsia is diminished remodelling of the spiral arteries by cytotrophoblast
This causes decreased blood flow and hence decreased nutrient supply to the placenta and fetus.
What is the treatment for IUGR and IUGR with pre-eclampsia?
Corticosteriods should be administered (if not already given) at gestations < 36 weeks in order to improve neonatal wellbeing, notably the development of the lungs.
For pre-eclampsia because the main issue is with the placenta, the ‘treatment’ is delivery
