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Flashcards in Fetal Circulation Deck (33)
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What are the adaptations that must happen at birth?

Cardiovascular adaptation
Pulmonary adaptation
Thermal adaptation


What special features does the fetal cardiovascular system have?

umbilical vein
ductus venosus
foramen ovale
ductus arteriosus
umbilical arteries


what does the umbilical vein do?

carries oxygenated blood from placenta


What does the ductus venosus?

oxygenated blood from placenta to IVC


what does the foramen ovale do?

mixed with deoxygenated blood coming from IVC


What does ductus arteriosus do?

mixed with deoxygenated blood coming from SVC


What does the umbilical arteries do?

mixture of oxygenated and deoxygenated blood from aorta to placenta


what is the blood haemoglobin level in the fetus?

20.7 g/dl


What is the blood volume in the fetus?

80-100 ml/kg


When does the ductus arteriosus close?

within the first few days of birth


What are the adaptations of extrauterine life?

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.


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

they will eventually fibrose to become supporting ligaments.


What benefits does delayed cord clamping have?

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


Fetal Breathing Movements

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


When are FBMs detectable by ultrasound?

around 10-11 weeks gestation


Why are FBM important?

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.


What is the surface of the alveolar cells made from?

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


What do macrophages do?

They remove particles and microorganisms coming with the air


Describe lung liquid.

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


What is the role of fetal lung liquid?

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.


What are the pulmonary adaptations?

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.


What does surfactant do?

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


What factors stimulate the first breath?

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


What is the respiratory rate like after birth?

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.


What happens to temp after birth?

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


At what rate do babies cool down?

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


Why do they lose heat so quickly?

the subcutaneous fat layer is thin and provides poor insulation


How is heat lost?

By evaporation, conduction, radiation and convection.

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


What to do at birth to help the babies temperature?

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


What is the Apgar score?