Fetal Circulation

Question 1

What are the adaptations that must happen at birth?

Answer 1

Cardiovascular adaptation
Pulmonary adaptation
Thermal adaptation

Question 2

What special features does the fetal cardiovascular system have?

Answer 2

umbilical vein
ductus venosus
foramen ovale
ductus arteriosus
umbilical arteries

Question 3

what does the umbilical vein do?

Answer 3

carries oxygenated blood from placenta

Question 4

What does the ductus venosus?

Answer 4

oxygenated blood from placenta to IVC

Question 5

what does the foramen ovale do?

Answer 5

mixed with deoxygenated blood coming from IVC

Question 6

What does ductus arteriosus do?

Answer 6

mixed with deoxygenated blood coming from SVC

Question 7

What does the umbilical arteries do?

Answer 7

mixture of oxygenated and deoxygenated blood from aorta to placenta

Question 8

what is the blood haemoglobin level in the fetus?

Answer 8

20.7 g/dl

Question 9

What is the blood volume in the fetus?

Answer 9

80-100 ml/kg

Question 10

When does the ductus arteriosus close?

Answer 10

within the first few days of birth

Question 11

What are the adaptations of extrauterine life?

Answer 11

Depends on the interplay between cardiovascular and respiratory system. Initiated within 60 seconds but may not be fully completed for a few week as the separation of the neonate from the placenta results in cessation of blood flow which collapses the umbilical vein and arteries.

Question 12

What happens to the ductus venosus and the hypogastric arteries after birth?

Answer 12

they will eventually fibrose to become supporting ligaments.

Question 13

What benefits does delayed cord clamping have?

Answer 13

in term of iron status as well as a more gentle adaptation to extrauterine life

Question 14

Fetal Breathing Movements

Answer 14

FBMs are episodic and irregular, interspersed with periods of apnea (suspension of breathing)

Question 15

When are FBMs detectable by ultrasound?

Answer 15

around 10-11 weeks gestation

Question 16

Why are FBM important?

Answer 16

FBMs in utero are vital for postnatal lung function. As gestation progresses, FBM increases in strength and frequency. the lunch fluid is breathed out into the amniotic fluid. Promotes growth and allows rehearsal of respiratory actions.

Question 17

What is the surface of the alveolar cells made from?

Answer 17

2 types of epithelial cells
Type 1: most of the alveolar surface (95%) is covered by type 1 cells, these are flattened cells, role in producing lung fluid

Type 2: produced surfactant; a lipoprotein, form a barrier between cells and air and would decrease the surface tension

Question 18

What do macrophages do?

Answer 18

They remove particles and microorganisms coming with the air

Question 19

Describe lung liquid.

Answer 19

During fetal life the lung develops as a liquid-filled organ. This liquid is produced by the fetal lung and leaves via the trachea from where it is either swallowed or enters the amniotic sac

Question 20

What is the role of fetal lung liquid?

Answer 20

Plays a crucial role in the growth and development of the fetal lungs by maintaining them in a distended state. It is now recognised that the retention of liquid within the future airways is required to maintain the lungs at an appropriate level of expansion in order to stimulate their growth.

Question 21

What are the pulmonary adaptations?

Answer 21

Production of surfactant from the 20th week. At term lungs are filled with 100mls of fluid (1/3 is expelled during birth and the rest is carried away by blood and lymphatic vessels). Development of lungs continues until about 8 years old.

Question 22

What does surfactant do?

Answer 22

reduced surface tension in the alveoli and assists gaseous exchange after birth

Question 23

What factors stimulate the first breath?

Answer 23

Changes in temp and tactile stimulation. Also surges of steroids and catecholamines associated with labour.

Question 24

What is the respiratory rate like after birth?

Answer 24

50 breaths per minute then down to 40. It is characteristically irregular with short periods of apnea and involves abdominal muscles. Inflation of a normal lung is completed with the first few breaths ad most alveoli expand within a few hours.

Question 25

What happens to temp after birth?

Answer 25

Babies are usually born into a cold and wet environment so they usually experience temperature loss

Question 26

At what rate do babies cool down?

Answer 26

0.2-1 degree per minute. Depending on environmental factors.

Question 27

Why do they lose heat so quickly?

Answer 27

the subcutaneous fat layer is thin and provides poor insulation

Question 28

How is heat lost?

Answer 28

By evaporation, conduction, radiation and convection.

The relatively large surface area of neonates means they are vulnerable to excessive heat loss.

Question 29

What to do at birth to help the babies temperature?

Answer 29

temp if birthing environment 21 degrees
close windows switch off fans
warm towels
dry wet skin at birth
skin to skin contact
Breastfeeding

Question 30

What is the Apgar score?

Answer 30

Appearance
Pulse
Grimace
Activity
Respiration

Question 31

what are the main things that must occur at birth for a successful transition to neonatal life?

Answer 31

conversion of fetal to neonatal circulation
initiation of breathing
thermoregulation

Question 32

What does successful breathing require?

Answer 32

adequate maturation of the lungs, particularly the presence of adequate surfactant and neuromuscular control, and clearance of lung fluid.

Question 33

What are the other adaptations to extrauterine life?

Answer 33

Establishment of breastfeeding
Elimination of waste through kidneys and gastrointestinal (digestive) system.
Communication development through parent child interactions