Session 9

Question 1

Describe the pattern of increase of fetal size, weight and body proportion

Answer 1

CRL increases rapidly
Weight gain slow at first then increases rapidly
Early fetus - protein deposition (muscles)
Late fetus - adipose deposition (preparing for life after birth)
9wks - head is half CRL
After 9 wks - body length and lower limb growth accelerate

Question 2

Describe the important events in the development of each of the major body systems

Answer 2

Respiratory:
Embryonic development - bronchopulmonary tree
Wks 8-16 - pseudoglandular stage (duct system beings to form, bronchioles)
Wks 16-26 - canalicular stage (formation of respiratory bronchioles)
Wks 26-term - terminal sac stage (differentiation of pneumocytes)
CVS:
Definitive fetal HR (15wks)
Urinary:
Fetal kidney function (10wks)
Fetal urine is a major contributor to amniotic fluid volume
Nervous:
First to begin development, last to finish
Corticospinal tracts required for coordinated voluntary movements
Myelination of brain begins in 9th month
16wks - cerebellar development
20wks - myelination
28wks - gyri and sulci appear, cerebellar hemispheres > skull
36wks - myelination in brain

Question 3

Describe how amniotic fluid is initially made

Answer 3

Maternal fluid (ECF) 
Diffuses to fetus due to non keratinised skin

Question 4

Define the terms ‘oligohydramnios’ and ‘polyhydramnios’ and reasons why they may occur in the fetus

Answer 4

Oligohydramnios - too little amniotic fluid ( placental insufficiency, renal impairment
Polyhydramnios - too much amniotic fluid (1500-2000ml) –> inability to swallow, anencephaly

Question 5

Describe the factors which influence the viability of the pre-term neonate

Answer 5

Development of respiratory system - type II pneumocytes usually produce surfactant
Otherwise respiratory distress syndrome

Question 6

Describe, in outline, the techniques used to assess fetal development

Answer 6

Fetal movements (quickening)
Respiratory movements, filling with fluid
Fetal heartbeat
Amniotic fluid
USS - calculate age, rule out ectopic, number of foetuses
CRL - estimate DD, check location, viability
Biparietal diameter
Abdominal circumference, femur length

Question 7

List the order of development of the major body systems

Answer 7

CNS
CVS
GI
UI
Resp

Question 8

Describe the fetal circulation and the changes which occur at birth

Answer 8

Fetal circulation - umbilical vein –> R heart (avoids liver with ductus venosus) –> L heart (via foramen ovale, ductus arteriosus) –> brain and rest of body –> umbilical artery
At birth - first breath, cold, trauma –> closure of shunts, functions as adult circulation

Question 9

Describe the processes involved in the control of amniotic fluid volume

Answer 9

Fetus swallows to absorb water and electrolytes, debris accumulates in gut –> meconium
Produced by fetal kidneys

Question 10

Describe the functions of amniotic fluid

Answer 10

Mechanical protection
Moist environment
Prevents adherence of embryo to amnion
Allows for fetal movements

Question 11

Describe oxygen transport in fetal blood

Answer 11

Oxygen diffuses across placenta due to gradient of partial pressures
Maternal pO2 high, fetal unbiblical venous pO2 low
Fetal pO2 in umbilical vein = 4pKa
Fetus has different Hb (70% saturated), no B chains, doesn’t readily bind 2,3 BPG, increased exposure to oxygen

Question 12

Describe carbon dioxide transport in fetal blood

Answer 12

Fetus cannot tolerate pCO2>mother’s pCO2
Facilitated by low maternal pCO2
Physiological hyperventilation and and dyspnoea stimulated by progesterone

Question 13

Explain why some babies be jaundiced at birth and how to overcome this

Answer 13

Billirubin excreted by mother via bile
Crosses placenta
Liver ability to conjugate billirubin stimulated by light exposure

Question 14

Define the ‘fetal period’

Answer 14

9-38 weeks post fertilisation
Growth and physiological maturation of the structures created in the embryonic period
Preparation for the transition to independent life after birth