Normal Fetal Growth

Question 1

What is the significance in historical data derived from failed pregnancies

Answer 1

historical data derived from failed pregnancies (miscarriages, stillbirths) has been superseded by data derived from ultrasound imaging

Question 2

Define foetal growth

Answer 2

Increase in mass that occurs between the end of embryonic period and birth

Question 3

What are the 2 components that foetal growth depends on

Answer 3

Genetic potential

Substrate supply

Question 4

What is genetic potential of foetal derived from and what is it mediated through

Answer 4

Derived from both parents

Mediated through growth factors eg insulin like growth factors

Question 5

What is substrate supply for foetal growth essential for and what is it derived from

Answer 5

Essential to achieve genetic potential

Derived from placenta which is dependent upon both uterine and placental vascularity

Question 6

What are the 3 phases of normal foetal growth

Answer 6

1. Cellular hyperplasia

2. Hyperplasia and hypertrophy 3. Hypertrophy alone

Question 7

What is symphysis fundal height

Answer 7

Distance over the abdominal wall from the pubic symphysis to the top of the uterus

Question 8

What may cause a symphysis fundal height that is smaller than normal

Answer 8

wrong dates
small for gestational age
oligohydramnios
transverse lie

Question 9

What may cause a symphysis fundal height that is larger than normal

Answer 9

wrong dates
molar pregnancy multiple gestation
large for gestational age Polyhydramnios 
Maternal obesity 
Fibroids

Question 10

What are the pros of SFH

Answer 10

Simple

Inexpensive

Question 11

What are the cons of SFH

Answer 11

Low detection rate (50-80%)
Great inter-operator variability
Influenced by many factors (BMI, foetal lie, amniotic fluid, fibroids)

Question 12

What are the 4 biometrical parameters assessed in ultrasounds for foetal growth

Answer 12

Crown Rump Length (CRL)
Head Circumference (HC)
Bi parietal diameter (BPD)
Abdominal circumference (AC)

Question 13

How are babies dated and what is the exception to this

Answer 13

Crown Rump Length (except IVF)

Question 14

What is the importance of correct dating

Answer 14

SGA or LGA confusion
Inappropriate inductions
Steroids in preterm delivery

Question 15

When is head circumference used for dating

Answer 15

HC is used if first scan is done after 14 weeks (CRL>84mm)

Question 16

Describe the normal growth curves

Answer 16

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

Question 17

Which factors influence foetal growth maternally

Answer 17

Poverty
Age
Drug use
Weight
Disease (hypertension, diabetes, coagulopathy)
Smoking and nicotine
Alcohol
Diet
Prenatal depression

Question 18

Which factors influence foetal growth foeti-placentally

Answer 18

Genotype - genetic potential
Gender (B>G)
Hormones
Previous pregnancy

Question 19

What are the 3 underlying principles to the customised standard that defines the individual foetal growth potential

Answer 19

1. Adjusted to reflect maternal constitutional variation maternal ht, wt, ethnicity, parity
2. Optimised by presenting a standard free from pathological factors such as diabetes and smoking
3. Based on fetal weight curves derived from normal pregnancies

Question 20

Why is obstetric ultrasound examination carried out

Answer 20

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