Normal Fetal Growth Flashcards
What is the significance in historical data derived from failed pregnancies
historical data derived from failed pregnancies (miscarriages, stillbirths) has been superseded by data derived from ultrasound imaging
Define foetal growth
Increase in mass that occurs between the end of embryonic period and birth
What are the 2 components that foetal growth depends on
Genetic potential
Substrate supply
What is genetic potential of foetal derived from and what is it mediated through
Derived from both parents
Mediated through growth factors eg insulin like growth factors
What is substrate supply for foetal growth essential for and what is it derived from
Essential to achieve genetic potential
Derived from placenta which is dependent upon both uterine and placental vascularity
What are the 3 phases of normal foetal growth
- Cellular hyperplasia
2. Hyperplasia and hypertrophy 3. Hypertrophy alone
What is symphysis fundal height
Distance over the abdominal wall from the pubic symphysis to the top of the uterus
What may cause a symphysis fundal height that is smaller than normal
wrong dates
small for gestational age
oligohydramnios
transverse lie
What may cause a symphysis fundal height that is larger than normal
wrong dates molar pregnancy multiple gestation large for gestational age Polyhydramnios Maternal obesity Fibroids
What are the pros of SFH
Simple
Inexpensive
What are the cons of SFH
Low detection rate (50-80%)
Great inter-operator variability
Influenced by many factors (BMI, foetal lie, amniotic fluid, fibroids)
What are the 4 biometrical parameters assessed in ultrasounds for foetal growth
Crown Rump Length (CRL)
Head Circumference (HC)
Bi parietal diameter (BPD)
Abdominal circumference (AC)
How are babies dated and what is the exception to this
Crown Rump Length (except IVF)
What is the importance of correct dating
SGA or LGA confusion
Inappropriate inductions
Steroids in preterm delivery
When is head circumference used for dating
HC is used if first scan is done after 14 weeks (CRL>84mm)
Describe the normal growth curves
Normal growth curves constructed from ultrasound measurements are expressed in centiles
They are used clinically to identify a normal intrauterine growth and detect risk of obstetric and neonatal complications
Which factors influence foetal growth maternally
Poverty Age Drug use Weight Disease (hypertension, diabetes, coagulopathy) Smoking and nicotine Alcohol Diet Prenatal depression
Which factors influence foetal growth foeti-placentally
Genotype - genetic potential
Gender (B>G)
Hormones
Previous pregnancy
What are the 3 underlying principles to the customised standard that defines the individual foetal growth potential
- 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
Why is obstetric ultrasound examination carried out
Assessment of fetal “wellness” not just size
Looking at trends in growth
Predicting fetal metabolic compromise
Anticipating the need to deliver prematurely
Liaising with Neonatal Services
