9. Fetal Growth And Development

Question 1

What happens generally in the embryonic period?

Answer 1

Organogenetic period - organs formed

Absolute growth is very small

Question 2

When does CRL (crown-rump length) increase rapidly?

Answer 2

Pre-embryonic
Embryonic
Early fetal periods

Question 3

Why is weight gain slow at first?

Answer 3

Embryo - intense morphogenesis and differentiation, little weight gain, placental growth most significant
Early fetus - protein deposition
Late fetus - adipose deposition

Question 4

How is fetal wellbeing monitored?

Answer 4

Mother - fetal movements
Regular measurements of uterine expansion - symphysis-fundal height
Ultrasound scan

Question 5

Why is USS used in pregnancy?

Answer 5

Safe
Can be used early in pregnancy to calculate age (and rule out ectopic/number of fetuses)
Routinely carried out at 20 weeks - asses fetal growth, fetal anomalies

Question 6

How is fetal age estimated?

Answer 6

Last menstrual period - prone to inaccuracy

Developmental criteria

Question 7

When is the crown-rump length measured?

Answer 7

Between 7 and 13 weeks to date the pregnancy and estimated EDD

Question 8

What is the biparietal diameter?

Answer 8

Distance between the parietal bones of the fetal skull
Used in combination with abdominal circumference and femur length for dating and growth monitoring
Useful for anomaly detection

Question 9

What are the classifications for birth weights?

Answer 9

3500g is average
<2500g suggests growth restriction
>4500g is macrosomia

Question 10

Why can babies have low birth-weight?

Answer 10

Premature
Constitutionally small
Suffering growth restriction - associated with neonatal morbidity and mortality

Question 11

What part of the respiratory system is formed in embryonic stage?

Answer 11

Bronchopulmonary tree

Question 12

When does functional specialisation of the respiratory system occur?

Answer 12

Fetal period

Question 13

What does the respiratory system develop from?

Answer 13

Primitive gut tube
Respiratory diverticulum comes off tube
Tracheoesophageal septum forms to separate trachea and oesophagus

Question 14

What happens in the pseudoglandular stage (weeks 8-16)?

Answer 14

Duct system begins to form within the bronchopulmonary segments created during the embryonic period - bronchioles

Question 15

What happens in the canalicular stage (weeks 16-26)?

Answer 15

Formation of respiratory bronchioles - budding from bronchioles formed during the pseudoglandular stage

Question 16

What happens in the terminal sac stage (weeks 26)?

Answer 16

Terminal sacs begin to bud from respiratory bronchioles

Differentiation of type I and type II pneumocytes - surfactant to minimise surface tension

Question 17

Why does the fetus make breathing movements?

Answer 17

Conditioning of respiratory musculature ready for birth

Ensures amniotic fluid moves into the lungs which is crucial for normal lung development

Question 18

When is the threshold of viability?

Answer 18

Only a possibility once the lungs have entered the terminal sac stage of development
>24 weeks

Question 19

What is respiratory distress syndrome?

Answer 19

Often affects infants born prematurely

Insufficient surfactant production

Question 20

What should be done if pre-term delivery is unavoidable or inevitable?

Answer 20

Glucocorticoid treatment of mother

Increases surfactant production in fetus

Question 21

When is the definitive fetal heart rate achieved?

Answer 21

Around 15 weeks

Question 22

When does fetal kidney function begin?

Answer 22

Week 10

Question 23

Is fetal kidney function necessary for survival in utero?

Answer 23

No, but without it there is oligohydramnios

Question 24

What can cause oligohydramnios?

Answer 24

Placental insufficiency

Fetal renal impairment

Question 25

What can cause polyhydramnios?

Answer 25

Fetal abnormality - e.g. inability to swallow

Question 26

When do corticospinal tracts required for coordinated voluntary movements begin to form?

Answer 26

4th month

Question 27

When does myelination of brain begin?

Answer 27

In 9th month

Question 28

When does movement of fetus start?

Answer 28

8th week

Question 29

What is quickening?

Answer 29

Maternal awareness of fetal movements from 15-17 weeks onwards