neonatal transition to extrauterine life

Question 1

what are the two main immediate changes

Answer 1

2 main immediate changes
Placenta blood exchange ceases
No placental exchange means oxygen is no longer delivered and co2 is no longer rmeoved
Lungs
Lungs inflate for the first time and take in air

Question 2

prior to birth

Answer 2

• Practice breathing
  
  • Surfactant production
  • Glycogen storage
  • Endocrine maturity
  • Brown adipose tissue
  • Fluid secretion to fluid absorption

Question 3

Practice breathing

Answer 3

• Fetal practice breathing is a process where the baby inhales and exhales small amounts of amniotic fluid
  
  • Essential for lung development and helps the baby prepare for life out of uterus

Question 4

Surfactant production

Answer 4

• Starting at 24wks start making a substance calling surfactant - which coats the alveoli and keeps them inflated when theirs are not of air in the lungs
  Adequate surfactant production is not until about 35 weeks , so infants born at that time have a much higher likelihood of independent breathing and survive than those born at 24 weeks

Question 5

glycogen storage

Answer 5

• Prior to birth the fetus depends on the maternal supply . A considerable portion of the placental transfer of glucose is used by the fetal brain .
  As fetus approaches term gestation glucose and other substrates are stored as glycogen in the liver - this can be converted to glucose for energy post birth

Question 6

Endocrine maturity - post birth

Answer 6

• Cortisol is the major regulatory hormone for terminal maturation of the fetus and for neonatal adaptation to birth .
  The cortisol surge is initiated with the switch from maternal transplacental derived corticosteroids to the ability of the fetus to make and release cortisol under their own control

Question 7

Endocrine maturity - catecholamines

Answer 7

• Catecholamines are norepinephrine , epinephrine and dopamine
  
  • Catecholamine surge is primarily responsible for the increase in blood pressure following birth , adaption of energy metabolism with support of the primary substrates for metabolism after birth glucose and fatty acids
  • Initiating thermogenesis from brown fat

Question 8

brown adipose tissue

Answer 8

Due to high surface area infants tend to lose more heat to the environment in comparison to adults
Evolution has provided humans with BAT tissue - a tissue that converts chemically stored energy in the form of fatty acids and glucose into heat through non shivering thermogenesi

Question 9

fluid secretion to absorption

Answer 9

• Clearance of Fetal lung fluid also begins before birth is enhanced by labour and rising cortisol levels mostly completed by 2 hours of age
  
  • During labour and immediately after birth the respiratory epithelium changes from active fluid secretion to active fluid absorption .
    Also increased pressure on the alveoli during inspiration drives fluid into the interstitial tissues where it can be removed by the pulmonary microcirculation and lymphatic vessels

Question 10

Immediate changes required at birth

Answer 10

Breathe - the baby when born needs to initiate its first breath and maintain regular respirations
Clear lungs - covert from fluid filled to air filled lungs
Redirected blood flow - transition from fetal circulation to neonatal circulation

Question 11

Initiation of respiration

Answer 11

• Elevated co2 level causes mild asphyxia (causes low levels of oxygen) this creates an overwhelming urge to intake air to supply the body with oxygen
  
  • When a baby is born vaginally subsequent and sudden changes in pressure this causes the chest to recoil or thoracic recoil
  • Tactile stimulation and proprioceptive stimuli - the unconscious perception of movement and spatial orientation arising from stimuli within the body itself
    Sudden temperature changes - cold stimulus to the skin activates the neonatal response to breathe

Question 12

ductus venosus

Answer 12

Ductus venosus - allow oxygenated blood to travel from the umbilical vein into the inferior vena cava

Question 13

foramen ovale

Answer 13

Foramen ovale - allows blood to move from right to left atrium - this then gets pumped up the ascending aorta

Question 14

Ductus arteriosis

Answer 14

small vessels between the pulmonary artery and the aorta that allows blood to travel through due the high pressure

Question 15

When the baby is born what happens

Answer 15

• Delayed cord clamping
  
  • Physiological processes are already in play that is decreasing the blood exchange from mum to baby

Question 16

Whartons jelly

Answer 16

• Is a gelatinous substance found in the umbilical cord
  
  • Surround and protect the blood vessels within the cord - providing a cushioning effect
  • Primary function of Whartons jelly during pregnancy is to insulate and support the umbilical vessels
  • However at birth when Wharton jelly is exposed to air and lower temperature - the cells constrict
  • This constriction slowly restrict the umbilical vessels - stopping blood flow

Question 17

When the cord stops the delivery and receipt of blood what happens to the Fetal circulatory pressures ?

Answer 17

Pressure of placental bed increase , the placenta was low resistance and then all of a sudden becomes high resistance .

Question 18

lungs

Answer 18

• As the resistance in the lungs fall the pulmonary artery pressure falls
  
  • Right side of the heart is working under low pressure because resistance in lungs has gone down
    Blood is now being oxygenated from the lungs

Question 19

Forman ovale closes

Answer 19

• Oxygenated blood delivered into left atrium
  
  • Pressure on right sides now lower pressure on left side is higher means that the foramen ovale closes in the first few minutes but can take up to 6 hours until fully closed
  • Closed foramen ovale becomes the fossa ovalis

Question 20

Ductus arteriosus close

Answer 20

• Severe physical factors causes the ductus arteriosus to close shortly after birth
  
  • First the ductus arteriosus senses increased oxygen levels in the blood and the vessels start to constrict
  • Secondly the ductus arteriosus detects a reduction in certain prostaglandins that are released by the placenta and again start to constrict
  • Usually fully closed first few hours of life
    Once closed becomes a fibrous cord known as the ligametum arteriosum

Question 21

Thermoregulation

Answer 21

Before birth the fetus is in a controlled warm environment , within the mothers womb
After birth neonates are exposed to a cooler external environment and they must quickly adapt to regulate their body temperature . Neonates also have a limited abilty to shiver effectively so they rely on non shivering thermogenesis

Question 22

brown adipose tissue

Answer 22

• Especially crucial for newborns in maintain body temperature
  
  • Neonates possess a higher proportion of brown adipose tissue compared to adults
  • Brown fat is rich in mitochondria has a blood supply - increased glycogen stores
    All these factors which facilitate rapid metabolism , heat production and transfer of heat outwards

Question 23

energy triangle

Answer 23

• Newborns who are not protected from heat loss produce more heat with activity and non shivering thermogenesis
  
  • Increased metabolic activity , neonatal cold stress can lead to hypoglycaemia and hypoxia
    Neutral thermal environment - environmental temperature at which basal metabolic demands are lowest

Question 24

Nutrition

Answer 24

· Before birth fetus is controlled in a warm environment , within the mothers womb and a relative stable temperature.
· After birth neonates are exposed to a cooler external environment and must quickly adapt to regulate their body temperature
· Neonates also have a limited ability to shiver effectively - so they rely more on non shivering thermogenesis
· neonate must maintain its own glucose levels
· Glucose is the major energy source and the fetus converts large amounts of glucose to glycogen and stores its liver , ready for extrauterine life.
· At birth , newborn glucose initially falls and insulin production will also decrease and glycogenesis is stimulated
Hepatic glycogen - mostly depleted by first 10 hours of life and newborn glucose production switches from glycogenolysis to gluconeogenesis

Question 25

Glycogenolysis

Answer 25

Glycogenolysis - release of glucose from glycogen

Question 26

Gluconeogenesis -

Answer 26

Gluconeogenesis - production of glucose from lactate and amino acids

Question 27

Excretion

Answer 27

Simple physiological process
Babies first bowel movement - meconium
Passage of meconium is initiated by gastrointestinal motility and the reflexes associated with the baby’s transition
Mechanical stimulation during the birthing process as well as the change in pressure , triggers expulsion of meconium
Meconium is usually passed within first 24 - 48