Foetal Growth And Develoment

Question 1

When is the foetal period?

Answer 1

Week 9-Birth

Question 2

What happens in the foetal period?

Answer 2

Growth and physiological maturation of the structures created during the embryonic period

Question 3

What are the patterns of growth during development?

Answer 3

Small increase in size and weigh during embryonic period but intense activity -organogenic

Big increase in size and weight in foetal period.

CRL increases

Question 4

How does Crown-Rump length change throughout pregnancy?

Answer 4

CRL increases rapidlyin the pre-embryonic, embryonic and early foeal periods.

• 9 weeks - 5cm
• 12 weeks - 8.5cm
• 20 weeks - 19cm
• 28 weeks - 28com

Question 5

How do the body proportions change through pregnancy?

Answer 5

Head takes up less space

At 9 weeks, the head is approx half the crl

Thereafter, body length and lower limb grwoth accelerate.

Question 6

How do you assess foetal wellbeing?

Answer 6

Mother - foetal movements

Regular measurements of uterine expansion - symphysis-fundal height

Ultrasound scan

Question 7

What is USS used for?

Answer 7

Used in early pregnancy to calculate age - rule out ectopic pregnancy, twins

Routinely carried out at 20 weeks - assess foetal growth, foetal abnormalities. Can also find out the sex at this point.

Question 8

How do we estimate foetal age?

Answer 8

First day of last menstrual period - prone to inaccuracy (spotting, irregular cycles)

Developmental criteria - allow for accurate estimation of foetal age.

Question 9

What developmental criteria can be used to date pregnancy?

Answer 9

Crown-Rump length - measured between 7-13 weeks to date the pregnancy and estimate date of delivery. Scan in T1 also used to check location, number and viability.

Biparietal diameter - The distance between the parietal bones of the foetal skull. Used in combination with other measurements to date pregnancies in T2 and T3.

Abdominal circumference and femur length - used in combination with BPD for dating and monitoring. Also used for anomalies.

Question 10

How do you classify birth weight?

Answer 10

3.5Kg = average

Under 2.5Kg = growth restriction

Over 4.5Kg = Macrosomia - common with diabetes.

Lots of things can increase birthweight not all pathological

Question 11

Why could babies be small?

Answer 11

Premature

Constitutionally small - small mums have small babies.

Growth restriction - neonatal morbidity and mortality.

Question 12

When do the lungs develop?

Answer 12

• The lungs develop relatively late
• Embryonic period - only bronchopulmonary tree
• Foetal period - Where functional specialisation occurs.
• This has implications for pre-term survival (cannot survive before 24 weeks as no alveoli or surfactant).

Question 13

How do lungs develop in weeks 8-16?

Answer 13

Pseudoglandular stage - make lots of airways

• Duct system begins to form within the bronchopulmonary segments created during the embyonic period. -Bronchioles

Question 14

How do the lungs develop in weeks 16-26?

Answer 14

Canalicular stage

Formation of respiratory bronchioles -Budding from bronchioles formed during the pseudoglandular stage.

Question 15

How do the lungs develop from 26 weeks - term?

Answer 15

Terminal sac stage.

Terminal sacs begin to bud from the respiratory bronchioles.

Differentiation of Type I and Type II pneumocytes. - Surfactant.

Question 16

Why does the foetus undergo breathing movements when the gas exchange is conducted at the placenta?

Answer 16

So the lungs can be prepared to breath at birth.

To condition the respiratory musculature and to fill them with amniotic fluid to aid in the development of the lung.

Question 17

What is the threashold for viability?

Answer 17

24 weeks - as no alveoli before that so can’t live.

Question 18

What is respiratory distress syndrome?

Answer 18

This often affects infants born pre-maturely

Insufficient surfactant production

If pre-term labour is unavoidable or inevitable - treat mother with glucocorticoids to increase the surfactant production on the foetus.

Question 19

When does the foetal heart rate occur for the first time?

Answer 19

15 weeks

Question 20

When does foetal kidney function begin?

Answer 20

9-10 weeks.

This is important as foetal urine is a major contributor to amniotic fluid volume.

Foetal kidney function is not necessary for survival in utero but without it there is oligohydraminos (too little amniotic fluid).

Question 21

What happens if there is an impairment of foetal kidney function, even though the kidney isn’t needed in utero?

Answer 21

Oligohydramnios - too little amniotic fluid.

Question 22

What is polyhydramnios?

Answer 22

Too much amniotic fluid.

Most often occurs because of foetal abnormalities - e.g. the inability to swallow (as usually swallows amniotic fluid).

Question 23

When does the nervous system develop?

Answer 23

Nervous system is the first to begin to develop and the last to finish.

Corticospinal tracts required for coordinated voluntary movements begin to form in the 4th month

Myelination of the brain only begins in 9th month -e.g. corticospinal tract myelination in incompletely birth, as evidence by increasing infant mobility in 1st year.

Question 24

When do the sensory and motor systems develop?

Answer 24

Not at all under 8 weeks.

After a large repitoire of movements develop. ‘Practising for post-natal life’ e.g. suckling, breathing

Question 25

What is “quickening”?

Answer 25

Maternal awareness of foetal movements from 17 weeks onwards (1st time mothers - if 2nd then earlier)

Low cost, simple method of ante-partum foetal surveillance

Reveal those foetuses requiring follow up.