4a: Fetal growth Flashcards
Where is most historical data about fetal growth from?
What is used today?
Historically: from miscariages (but problem: often fetus that have growth restiction are more likely to die)
Now: ultrasound
How does fetal growth (e.g. measured crown-rump length) change during pregnancy?
Growth is essentially a - exponential curve
- Very fast at first and then gets slower and slower
How does fetal weight change during pregnancy?
Curve: historical data differnet from the actual numbers (because derived from miscarriages)
Actual numbers:
- 14-15 wks: 5g /day
- 20 wks: 10 g/day
- 32-34 wks: 30-35g/day –> Mainly in 3rd trimester
- >34 wks: growth rate decreases
What is fetal growth?
Increase in mass that occurs between the end of embryonic period and birth
What are the 2 components that determine fetal growth?
2 components
- Genetic potential
- genetics from parents
- (mediated through growht Factors e.g. insulin)
- Substrate supply
- essential to achieve genetic potential
- derived from placenta which is dependent upon both uterine and placental vascularity
What are the three phases in normal fetal growth?
- Cellular hyperplasia (4-20W)
- Hyperplasia and hypertrophy (20-28 Weeks)
- Hypertrophy alone (28-40W)
What are the differnet parameters that are used to assess fetal growth?
Via ultrasound measured
- Biparietal diameter (BPD),
- Head Circumference (HC),
- Abdominal Circumference (AC) and Femur Length (FL)
They are combined to give the Estimated Fetal Weight (EFW).
How is normal growth assessed once all the important parameters are assesed?
Via Percentiles:
- allows normal minitoring of differnet sized that are still normal
What would be problematic: shift in percentile
Explain the role and use of customised fetal growth charts
Percentile curves altered to give more accurate prediction of what is normal based on
- fetal weight curves for normal pregnancies, free from pathological factors (e.g. smoking, diabetis)
- adjusted maternal variation e.g. maternal height, weight, ethnicity, parity.
Explain the role and assessment of abdominal palpation and dating of pregnancies and assesment of fetal growth
Dating: With Symphysis fundal height (via abdnominal palpation
- 1cm about 1 Week (+/-)
- But: not very acurate so dating should now be perfomed on US measurements
- limitations: wrong last menstrual period date, the baby in a transverse lie, or complications including oligohydramnios (low levels of amniotic fluid) or a baby that is small for gestational age (SGA)
What are the advantages and disadvanatges of mearuign SFH
Symphisis Fundal Height
Pro:
- Simple
- Inexpensve
Con:
- Low detection rate: 50-86%
- Great inter-operator variability
- Influenced by a number of factors (BMI, fetal lie, amniotic fluid, fibroids)
How shoud pregnancies be dated now?
What other measurements could also be used?
Now: Should be dated via Crown rump lengh
Because other ways of dating can be inaccurate
- Last Menstrual Period: irregular periods; abnormal bleeding; oral contraceptives, breastfeeding)
Which factors influence fetal growth?
There are Maternal and feto-placental factors that influence fetal growth
What are the maternal factors that influence fetal growth?
- Poverty
- Age (healthy 16-35)
- Drug use
- Smoking/Nicotine
- Alcohol
- Diet
- Weight
- Disease
- hypertension
- diabetes
- coagulopathy
- Prenatal depression
- Environmental toxins
Which fetal factors influence fetal growth?
Feto-placental
- Genotype: genetic potential
- Gender (B>G)
- Hormones
- somatotrophin
- FHS/LH
- Insulin
- Thyorid
- Andorgens
- Previous pregnancy
