Fetal Growth and Development

Question 1

What is Crown Rump length?

Describe its pattern of increase

Answer 1

Length of fetus (from head to tail)

Increases linearly in Pre-embryonic, Embryonic and Fetal periods

Question 2

Weight gain is slow at first, then increases rapidly in mid and late fetal periods.

What tissues are deposited in the Early and Late fetus

Answer 2

Early fetus- Protein due to muscle development

Late fetus- Adpiose for metabolic purposes and heat regulation

Question 3

Describe the Proportion of growth as pregnancy progresses

Answer 3

• Initally (week 9), the head is 50% of the length of the fetus
• At delivery, the head is 25% of the length of the fetus

Question 4

List 3 ways of assessing fetal wellbeing

Answer 4

• Ask the mother
• Symphysis-fundal height
• USS

Question 5

How does asking the mother help to asses fetal well-being

Answer 5

Fetal movements begin at 20 weeks and mother will be able feel this as well as any changes that may occur

Question 6

How can the Symphysis-Fundal height be used to asses fetal wellbeing?

Answer 6

• From Pubic Symphysis to Fundus of Uterus
• At week 20, SFH should be at Umbilicus
• After week 20, SFH should equal week of pregnancy (E.g 28 cm at week 28)

Question 7

Suggest and explain 2 causes of the Symphisis-Fundal height being larger than normal.

Answer 7

• Swallowing difficulties
• Excessive Urine production

Lead to Polyhydramnios (excess amniotic fluid)

Question 8

Suggest 3 causes of the Symphisis-Fundal height being lower than normal.

Answer 8

• Intrauterine Growth Restriction
• (Oligohydramnios) Lack of amniotic fluid production
• As fetal head engages (head positions closer to cervix) in pelvis

Question 9

Suggest 3 ways of using USS to assess fetal wellbeing

Answer 9

• Estimate date of pregnancy
• Rule out Ectopic IF DONE TRANSVAGINALLY
• Identify multiple pregnancy

Question 10

Why is a ‘20 week scan’ routinely done?

Answer 10

Most structures have developed by this point and are visible on an Ultrasound

(And to asses growth)

Question 11

List 3 genetic conditions that can be screened for via a combination of USS and Blood tests

Between what weeks is this done?

Answer 11

• Down’s Syndrome
• Edwards’ Syndrome (Rare to survive into adulthood)
• Patau’s Syndrome (Rare to survive into adulthood)

Weeks 10 and 14 (offered to all pregnant women)

Question 12

Outline 2 broad types of methods used to estimate Fetal age

Answer 12

• Last Menstrual Period, LMP: Look at first day of LMP (Prone to inaccuracy)
• Use of Developmental Criteria: Comparing USS measurements to a ‘normal’ value

Question 13

What are 3 developmental criteria used to estimate fetal age?

Answer 13

• CRL
• Biparietal diameter
• Abdominal Circumference

Question 14

Between what weeks can CRL be used as developmental criteria to estimate fetal age?

Why is it a good method?

Answer 14

• 7 and 13

- Good method due to linear nature of progression

Question 15

Describe the use of Biparietal Diameter as developmental criteria to estimate fetal age

Why is CRL not used?

Answer 15

• Distance between parietal bones in Fetal skull
• Used in Trimesters 2 and 3
• Correlation between CRL and age is less accurate in later pregnancy

Question 16

Describe the use of Abdominal Circumference as developmental criteria to estimate fetal age

Answer 16

• Used in combination with Biparietal Diameter
• In Trimesters 2 and 3
• Widest part of abdomen, often in combination with Femur length

Question 17

What is the average range of Fetus weight?

Answer 17

2.5kg-4.5kg (Average is 3.5kg)

<2.5: Growth restriction
>4.5: Macrosomia

Question 18

List 3 causes of Low birth weight

List the most common cause of High birth weight

Answer 18

• Premature
• Growth restriction
• Constitutionally small (Small mother)
• Poorly controlled Gestational Diabetes

Question 19

Outline the development of the Respiratory System

Answer 19

• Lungs develop relatively late
• As an out-pouching of the Foregut to create the Bronchopulmonary Tree in the Embryonic Period
• Further specialisation in the Fetal Period

Question 20

Describe the development of the Respira System in the Embryonic Period after the BP Tree has formed

Answer 20

Pseudoglandular stage (Week 8-16);
- Budding and Branching of Bronchioles

Canalicular stage (Week 16-26);
- Further branching-> Respiratory Bronchioles

Terminal Sac stage (Week 26 onwards);

• Terminal sacs bud from Respiratory Bronchioles
• Type I and II Pneumocytes develop and produce Surfactant

Question 21

What determines Fetal ‘Viability’?

Answer 21

Whether or not Pneumocytes are present (Surfactant production required otherwise-> Premature delivery or Pregnancy termination)

Question 22

What do you do if Premature delivery is unavoidable, to stimulate fetal surfactant production?

Answer 22

Give Glucocorticoids

Question 23

What is an average range of fetal heart rate?

When is this heart rate achieved?

Answer 23

110-160 BPM

At Week 15

Question 24

When does Fetal urine production start?

Is Fetal Kidney function necessary for survival?

Answer 24

Week 9/10 in Fetal Period

Not necessary as Placenta handles majority of waste excretion
However reduced function-> Oligohydramnios

Question 25

Suggest 2 causes of Oligohydramnios (Too little amniotic fluid)

Answer 25

• Placental insufficiency

- Reduced fetal Renal function

Question 26

Suggest 3 causes of Polyhydramnios (Too much amniotic fluid)

Answer 26

• Can be a variation of normal

Issue recycling amniotic fluid;

• Issues swallowing (CNS defect possibly)
• Congenital abnormalities

Question 27

Why is the Nervous System most vulnerable to injury during the developmental process?

What structures are needed for Coordinated Voluntary movements?
When do these structures form?

Answer 27

• First to start developing, Last to finish

- Corticospinal Tracts, begin to form in Month 4

Question 28

When does Myelination of the Corticospinal Tracts begin?

Supply 1 piece of evidence of this

Answer 28

Month 9 (Incomplete at birth)

Baby unable to walk/ perform other coordinated movements until age of 1

Question 29

What movement does the Fetus do in practice for breastfeeding in the Fetal Period

Answer 29

Sucking its thumb

Question 30

What is the earliest time a mother can sense the fetus moving?

What is this Phenomenon called?

Answer 30

Week 17, called ‘Quickening’