Foetal Growth and Development

Question 1

Describe the pattern of weight gain in the foetus. (2)

Answer 1

Initially protein is laid down, then adipose for metabolism and heat regulation.

Question 2

What is crown-rump length? (1)

Answer 2

A measurement from the head to the tail of the foetus that is an indicator of gestational age.

Question 3

Describe the three most common ways to assess foetal wellbeing in pregnancy. (8)

Answer 3

Symphysis-fundal height: cm=week of pregnancy. 12 weeks: pubic symphysis, 20: umbilicus, 36: xiphoid process, term: regresion to 34cm.
USS: 12 week scan used to assess for ectopic and multiple pregnancy, and to assess foetal age through crown-rump. 20 week scan is used to assess abnormalities - structures big enough to see but before the 24 week abortion deadline.
Ask the mother: after 20 weeks the mother can sense movement.

Question 4

Describe ways of estimating foetal age. (5)

Answer 4

Number of days since the start of the last menstrual period.
Crown-rump length - useful in early pregnancy.
Biparietal diameter
Abdominal circumference
Femur length

Question 5

Describe the classifications of birth weights and some causes of abnormalities here. (8)

Answer 5

Average - 3.5kg - 7lb 7
Microsomia - <2.5kg - <5lb 5 - premie, growth restriction, small mother.
Macrosomia - >4.5kg - >9lb 9 - gestational diabetes.

Question 6

Describe the development of the respiratory system in the foetus. (7)

Answer 6

Develops late from an outpouch of foregut that forms the bronchopulmonary tree. Branching of the bronchioles occurs in weeks 8-16 (pseudoglandular stage) and respiratory bronchioles from weeks 16-26 (canalicular stage).
Terminal sacs develop in weeks 26-40, and surfactant begins to be produced.

Question 7

Describe why premies often struggle to breath and what can be done if premature birth is inevitable. (2)

Answer 7

Because their pneumocytes haven’t get begun to produce surfactant.
Give the mother glucocorticoids to prompt surfactant production.

Question 8

Describe the foetal cardiovascular system. (6)

Answer 8

Ductus venous directs blood from umbilical vein around the liver to allow brain and heart to have heavily oxygenated blood.
Ductus arteriosus allows blood between the pulmonary trunk and the aorta so only blood needed for development flows though the lungs, not the entire circulating volume.
Foramen ovale exists between the right and left atria to allow oxygenation of blood to remain high.
Normal term heart rate is 110-160bpm, important to assess bradycardia in foetal distress.

Question 9

Explain why amniotic fluid volume is a good measure of kidney function. (2)

Answer 9

Because the foetal kidney is responsible for the production of a lot of the amniotic fluid so having too much or too little is an indicator of inadequate kidney function.

Question 10

Define polyhydraminos and oligohydraminos. (5)

Answer 10

Polyhydraminos - too much amniotic fluid, a variant of normal, or an issue with recycling of amniotic fluid eg CNS deficit relating to swallowing, or abnormalities with swallowing.
Oligohydraminos - too little amniotic fluid could indicate placental insufficiency or a kidney problem.

Question 11

Explain why the nervous system is likely to be damaged during development. (2)

Answer 11

First to start development, last to finish - longer time slot increases chances of damage occurring.

Question 12

Explain the development of movements in utero. (3)

Answer 12

Co-ordinated movements require a tract called the corticospinal tract which begins to form in the 4th month (why mothers feel the quickening at 20 weeks).

Question 13

Explain why babies can’t walk at birth like other mammals. (2)

Answer 13

At birth, their corticospinal tracts aren’t myelinated, so co-ordinated movements aren’t possible.