Fetal Growth (21.02.2020)

Question 1

What is foetal growth?

Answer 1

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

Question 2

What components does foetal growth depend on?

Answer 2

Genetic potential

• derived from both parents
• mediated through growth factors eg insulin like growth factors

Substrate supply

• essential to achieve genetic potential
• derived from placenta which is dependent upon both uterine and placental vascularity

Question 3

Normal fetal growth is characterised by 3 subsequent phases: what are they?

Answer 3

Normal fetal growth is characterised by 3 subsequent phases:

1. Cellular hyperplasia (20th week onwards)
2. Hyperplasia and hypertrophy (20-28w)
3. Hypertrophy alone (28w +) - fat, muscle, tissue

Question 4

How fast does a foetus grow?

Answer 4

Weight gain
14-15 wks: 5g /day
20 wks: 10 g/day
32-34 wks: 30-35g/day
>34 wks: growth rate decreases

Question 5

SFH

Answer 5

• symphysis fundal height

- quick bedside assessment

Question 6

What can go wrong wehen measuring SFH?

Answer 6

Larger

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

Smaller

• wrong dates
• small for gestational age
• oligohydramnios
• transverse lie

Question 7

Pros and Cons

Answer 7

Simple
• Low detection rate: 50-86%

Inexpensive
• Great inter-operator variability
• Influenced by a number of factors (BMI, fetal lie, amniotic fluid, fibroids)

Question 8

Dating of preganncies

Answer 8

Dating by LMP:
Inaccurate (irregular periods; abnormal bleeding; oral contraceptives, breastfeeding)

Importance of correct dating:
• SGAorLGAconfusion
• Inappropriate inductions
• Steroids in preterm delivery

All pregnancies should be dated by CRL except IVF pregnancies

Question 9

CRL

Answer 9

crown rump length

Question 10

Ultrasound assessment of fetal growth

Answer 10

• Fetal growth is assessed by 4 biometrical parameters (BPD, HC, AC, FL) and their combination (EFW)
• 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 11

What factors can influence foetal growth?

Answer 11

Maternal
• Poverty
• Age
• Drug use
• Weight
• Disease
– hypertension – diabetes
– coagulopathy
• Smoking and nicotine
• Alcohol
• Diet
• Prenatal depression
• Environmental toxins

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

Question 12

Customised growth charts

Answer 12

The customised standard defines the individual fetal growth potential by three underlying principles:

1. Adjustedtoreflectmaternalconstitutionalvariation 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