EXAM 4 MATERNAL
(9) Physiological Transition of the Newborn
ADAPTATIONS OF THE RESPIRATORY SYSTEM
Intrapulmonary Fluid, Fetal Breathing, Movements, Surfactant
● INITIATION → RESPIRATIONS = FIRST important step → Neonatal Transition
● LUNG EXPANSION (Post-birth) → Stimulates release → SURFACTANT
○ Surfactant: Slippery, detergent-like phospholipid; Lecithin + Sphingomyelin
■ Prevents ALVEOLAR COLLAPSE (Re-expansion + Gas exchange)
■ 35 weeks gestation → Sufficient Surfactant levels → Stability
○ Lung Maturity Assessment: L/S ratio
■ 2:1 = Mature lungs
■ Less Lecithin (ex. 1:2) = Immature lungs + Requires Steroid administration
The First Breath (Initiation of Respirations)
Each of these factors stimulates the respiratory center located within the MEDULLA of the brain
● Chemical Factors
1. Hypoxia → Blood oxygen levels (PO2) + pH → Drop ↓
2. Leads → Hypercarbia → (PCO2) Rises ↑ → Acidosis
3. Infant takes FIRST BREATH to offset Carbon Dioxide
○ Prolonged Asphyxia → Respiratory depression (CNS)
● Sensory Factors
○ Overwhelming Stimuli when leaving a familiar, comfortable, warm environment
○ Stimulation Technique: Vigorous rubbing → Awakens infant + Initiates respirations
● Thermal Factors
○ Drastic change in temperature from womb to outside world
○ Normal Range: 97.7 ℉ - 98.6 ℉
○ Prevent Cold Stress/Respiratory Depression: Immediately Dry infant + Skin-to-Skin/Radiant
Warmer
● Mechanical Factors
○ Removal of fluid from lungs → Replacing it with air
○ Fetal chest compression + Thoracic squeeze (Vaginal birth) → Increases intrathoracic pressure →
Pushes fluid out of lungs
○ Recoil of chest wall (Post-birth) → Negative intrathoracic pressure → Small inspiration of air
○ Cesarean birth → Higher risk for pulmonary transitional difficulties *
○ Most fluid = Reabsorbed within the first few hours → Some infants require 24 hours
■ Newborn lungs may sound moist during early auscultation
Factors That May Interfere With Respiration
● RF : Prematurity + Birth Asphyxia
● Born before 35 weeks (Premature) → LOW SURFACTANT → RESPIRATORY DISTRESS SYNDROME (RDS)
○ Occurs most frequently in newborns with immature lungs
○ Lack of Surfactant → Prolonged atelectasis → Poor lung compliance
○ Labor before 35 weeks → Steroid injection → Increase Surfactant + Prevent alveolar collapse
1
,Cardiopulmonary Transition
● Air enters lungs → PO2 rises in alveoli
○ Pulmonary artery relaxation → Decrease in pulmonary vascular resistance
○ Pulmonary blood flow increases → 100% → First 24 hours
○ Once pulmonary circulation is established → Blood = Distributed throughout lungs
● Fetal Hemoglobin (HbF) → Greater affinity for oxygen // Greater oxygen saturation vs. Adults
○ Adult Hemoglobin (HbA)
● Assessment of Cardiopulmonary system must occur IMMEDIATELY after birth
○ Skin color = Most important indicator
○ Normal: Central pink hue + Acrocyanosis: Bluish coloration of hands + feet (Persists for 24 hours)
○ Cyanosis: Bluish/Purple lips, extremities, or abdomen (Darker skin → Blue mucous membranes)
○ Normal Respiratory Rate: 30-60 breaths per minute
○ Normal Breathing Pattern: Shallow, diaphragmatic, and irregular + Synchronous Abd/Chest
■ Periodic Breathing: Brief pauses → 5-15 seconds
● No association w/ change in skin color/HR
■ Apnea: Cessation of breathing lasting >20 seconds = ABNORMAL
● Associated w/ change in skin color + DECREASE in HR (<100 BPM)
● REPORT APNEA IMMEDIATELY
○ Signs of Respiratory Distress:
■ Expiratory grunting
■ Wheezing
■ Nasal flaring
■ Retractions
■ Use of accessory muscles at rest
■ Breathing rate outside of normal range
CARDIOVASCULAR ADAPTATION
Changes After Placental Expulsion
● Utero → Placenta = Oxygen/Nutrient delivery system + Excretion of Waste (Carbon Dioxide)
○ Fetal Blood Flow: Oxygenated blood enters → Umbilical vein
○ 40-60% perfuses the Liver → The rest bypasses it through the Ductus Venosus
○ Blood reaches the heart (Right Atrium) via Inferior Vena Cava
● Placenta Separation → Umbilical Arteries + Vein constrict
● Five Major Changes:
1. Increased aortic pressure + Decreased venous pressure
2. Increased systemic pressure + Decreased pulmonary pressure
3. Closure of foramen ovale
4. Closure of ductus arteriosus
5. Closure of ductus venosus
● Closure of the Foramen Ovale
○ What is it?Flap in heart that allows blood flow between the right/left atria, bypassing the lungs
○ How it closes :
■ Clamping cord → STOPS Placental Blood flow
■ Increased LEFT atrial pressure (pulmonary vein return)
■ Decreased RIGHT atrial pressure (reduced flow from inferior vena cava)
■ Pressure change CLOSES the flap
○ When does it functionally close?
■ 1-2 hours after birth
○ When does it permanently close?
■ 6 months of life
○ What does it transform into?
■ Fossa Ovalis
○ Complications: Asphyxia, Acidosis, or Cold Stress → Shunt may re-open → Continued R-L Shunting
(Due to increased pressure in the Right Atria)
2
, ● Closure of the Ductus Arteriosus
○ Vessel connecting pulmonary artery → descending aorta, bypassing the lungs
What is it?
○ How it closes:
■ Cord clamping: INCREASES Systemic Vascular Resistance
■ INCREASED Oxygen levels (Lung expansion) → Triggers VASOCONSTRICTION
■ Functional closure occurs
○ When does it functionally close?
■ 72 hours after birth
○ When does it permanently close?
■ 3-4 weeks of life
■ Due to endothelial destruction, connective tissue formation, and subintimal proliferation
○ What does it transform into?
■ Ligamentum Arteriosum
○ Complications: Prematurity/Asphyxia → Closure may fail → Patent Ductus Arteriosis (PDA)
■ PDA → Abnormal blood flow → Murmur (Left sternal border/2nd intercostal space)
● Closure of the Ductus Venosus
○ What is it? Vessel connecting Umbilical Vein → Inferior vena cava, bypassing liver
○ How it closes:
■ Cord clamping: STOPS blood flow through umbilical vein
■ Pressure changes redirect blood → Liver
■ Functional closure occurs + Fibrosis converts it → Ligamentum Venosum
○ When does it functionally close?
■ 1 week after birth
○ What does it transform into?
■ Ligamentum Venosum
Structure Fetal Function Closure Trigger Functional Closure Permanent Closure
Foramen Ovale Right-to-leftshunt Increased LEFT 1-2 hours 6 months
between atria atrial pressure (Fossa Ovalis)
(bypassing lungs) (Pressure changes
between atria)
Ductus Arteriosus Right-to-left shunt Increased Lung 72 hours 3-4 weeks
from pulmonary OXYGENATION (Ligamentum
artery to aorta Arteriosum)
Ductus Venosus Bypasses LIVER → Cessation of 1 week End of Infancy
Sends blood Umbilical Vein Blood (Ligamentum
through Inferior flow Venosum)
Vena Cava (Cord Clamping →
Stops venous
return)
3
, THERMOGENIC ADAPTATION
Thermoregulation = Essential for Survival
Homeothermic : Attempt at regulating/maintaining internal core temperatures regardless of external environment
The Neutral Thermal Environment
● R/T Oxygen Consumption + Metabolism
● Neutral Thermal Environment (NTE): Temperature range where newborn can maintain their body
temperature with MINIMAL oxygen consumption + metabolic demands
○ Thermoregulation Mechanisms:
■ Vasoconstriction: Constricts blood vessels to CONSERVE heat
■ Vasodilation: Expands blood vessels to RELEASE heat
● Normal (Axillary) Temperature: 97.7 ℉ - 98.6 ℉ (Within 2-3 hours after birth)
● Decreased Adipose/Sub-Q Fat → Risk of HEAT LOSS
● Flexed Position → Reduces body surface area + CONSERVES HEAT
○ Preterm infants: Lack muscle tone for flexion → Vulnerable to HEAT LOSS
● Cold Stress: When the newborn CANNOT maintain body temperature in response to the environment
○ Causes:
■ Increased OXYGEN CONSUMPTION + Metabolic rate (MORE DEMANDS)
■ Rapid depletion of BAT
■ Potential for HYPOGLYCEMIA + HYPOXIA + METABOLIC ACIDOSIS
Physiological Adaptations for Heat Production
● To Increase Heat Production:
○ Increased Basal Metabolic Rate → Boosts energy expenditure for heat generation
○ Increased Muscle Activity → Promotes heat production through movement
○ Peripheral Vasoconstriction → Constricts blood vessels to reduce heat loss
○ Nonshivering Thermogenesis (NST): Primary Mechanism for Heat Production *
■ NEWBORNS CANNOT SHIVER
■ Trigger: Skin receptors detect → DROP in temperature → Alert SYMPATHETIC nervous
system → ACTIVATE NST
■ Process: Brown Adipose Tissue (BAT) → RAPID METABOLISM of Triglycerides → Generates
heat → Distributed to peripheral circulation (Highly vascularized brown fat cells)
■ Sites of BAT: Midscapular area, Neck/Axillae, Trachea, Esophagus, Abdominal aorta,
Kidneys, Adrenal glands
○ Brown Adipose Tissue (BAT):
■ Formation → 26-30 weeks gestation
■ Peak storage → 2-5 weeks post-birth
■ Highly vascularized + Abundant blood vessels, cells, and nerve endings
■ Efficient at metabolizing TRIGLYCERIDES → Heat Production
■ RISK: COLD STRESS → RAPIDLY depletes BAT reserves → HYPOTHERMIA
● BAT CANNOT BE RESTORED/REGENERATED
4
(9) Physiological Transition of the Newborn
ADAPTATIONS OF THE RESPIRATORY SYSTEM
Intrapulmonary Fluid, Fetal Breathing, Movements, Surfactant
● INITIATION → RESPIRATIONS = FIRST important step → Neonatal Transition
● LUNG EXPANSION (Post-birth) → Stimulates release → SURFACTANT
○ Surfactant: Slippery, detergent-like phospholipid; Lecithin + Sphingomyelin
■ Prevents ALVEOLAR COLLAPSE (Re-expansion + Gas exchange)
■ 35 weeks gestation → Sufficient Surfactant levels → Stability
○ Lung Maturity Assessment: L/S ratio
■ 2:1 = Mature lungs
■ Less Lecithin (ex. 1:2) = Immature lungs + Requires Steroid administration
The First Breath (Initiation of Respirations)
Each of these factors stimulates the respiratory center located within the MEDULLA of the brain
● Chemical Factors
1. Hypoxia → Blood oxygen levels (PO2) + pH → Drop ↓
2. Leads → Hypercarbia → (PCO2) Rises ↑ → Acidosis
3. Infant takes FIRST BREATH to offset Carbon Dioxide
○ Prolonged Asphyxia → Respiratory depression (CNS)
● Sensory Factors
○ Overwhelming Stimuli when leaving a familiar, comfortable, warm environment
○ Stimulation Technique: Vigorous rubbing → Awakens infant + Initiates respirations
● Thermal Factors
○ Drastic change in temperature from womb to outside world
○ Normal Range: 97.7 ℉ - 98.6 ℉
○ Prevent Cold Stress/Respiratory Depression: Immediately Dry infant + Skin-to-Skin/Radiant
Warmer
● Mechanical Factors
○ Removal of fluid from lungs → Replacing it with air
○ Fetal chest compression + Thoracic squeeze (Vaginal birth) → Increases intrathoracic pressure →
Pushes fluid out of lungs
○ Recoil of chest wall (Post-birth) → Negative intrathoracic pressure → Small inspiration of air
○ Cesarean birth → Higher risk for pulmonary transitional difficulties *
○ Most fluid = Reabsorbed within the first few hours → Some infants require 24 hours
■ Newborn lungs may sound moist during early auscultation
Factors That May Interfere With Respiration
● RF : Prematurity + Birth Asphyxia
● Born before 35 weeks (Premature) → LOW SURFACTANT → RESPIRATORY DISTRESS SYNDROME (RDS)
○ Occurs most frequently in newborns with immature lungs
○ Lack of Surfactant → Prolonged atelectasis → Poor lung compliance
○ Labor before 35 weeks → Steroid injection → Increase Surfactant + Prevent alveolar collapse
1
,Cardiopulmonary Transition
● Air enters lungs → PO2 rises in alveoli
○ Pulmonary artery relaxation → Decrease in pulmonary vascular resistance
○ Pulmonary blood flow increases → 100% → First 24 hours
○ Once pulmonary circulation is established → Blood = Distributed throughout lungs
● Fetal Hemoglobin (HbF) → Greater affinity for oxygen // Greater oxygen saturation vs. Adults
○ Adult Hemoglobin (HbA)
● Assessment of Cardiopulmonary system must occur IMMEDIATELY after birth
○ Skin color = Most important indicator
○ Normal: Central pink hue + Acrocyanosis: Bluish coloration of hands + feet (Persists for 24 hours)
○ Cyanosis: Bluish/Purple lips, extremities, or abdomen (Darker skin → Blue mucous membranes)
○ Normal Respiratory Rate: 30-60 breaths per minute
○ Normal Breathing Pattern: Shallow, diaphragmatic, and irregular + Synchronous Abd/Chest
■ Periodic Breathing: Brief pauses → 5-15 seconds
● No association w/ change in skin color/HR
■ Apnea: Cessation of breathing lasting >20 seconds = ABNORMAL
● Associated w/ change in skin color + DECREASE in HR (<100 BPM)
● REPORT APNEA IMMEDIATELY
○ Signs of Respiratory Distress:
■ Expiratory grunting
■ Wheezing
■ Nasal flaring
■ Retractions
■ Use of accessory muscles at rest
■ Breathing rate outside of normal range
CARDIOVASCULAR ADAPTATION
Changes After Placental Expulsion
● Utero → Placenta = Oxygen/Nutrient delivery system + Excretion of Waste (Carbon Dioxide)
○ Fetal Blood Flow: Oxygenated blood enters → Umbilical vein
○ 40-60% perfuses the Liver → The rest bypasses it through the Ductus Venosus
○ Blood reaches the heart (Right Atrium) via Inferior Vena Cava
● Placenta Separation → Umbilical Arteries + Vein constrict
● Five Major Changes:
1. Increased aortic pressure + Decreased venous pressure
2. Increased systemic pressure + Decreased pulmonary pressure
3. Closure of foramen ovale
4. Closure of ductus arteriosus
5. Closure of ductus venosus
● Closure of the Foramen Ovale
○ What is it?Flap in heart that allows blood flow between the right/left atria, bypassing the lungs
○ How it closes :
■ Clamping cord → STOPS Placental Blood flow
■ Increased LEFT atrial pressure (pulmonary vein return)
■ Decreased RIGHT atrial pressure (reduced flow from inferior vena cava)
■ Pressure change CLOSES the flap
○ When does it functionally close?
■ 1-2 hours after birth
○ When does it permanently close?
■ 6 months of life
○ What does it transform into?
■ Fossa Ovalis
○ Complications: Asphyxia, Acidosis, or Cold Stress → Shunt may re-open → Continued R-L Shunting
(Due to increased pressure in the Right Atria)
2
, ● Closure of the Ductus Arteriosus
○ Vessel connecting pulmonary artery → descending aorta, bypassing the lungs
What is it?
○ How it closes:
■ Cord clamping: INCREASES Systemic Vascular Resistance
■ INCREASED Oxygen levels (Lung expansion) → Triggers VASOCONSTRICTION
■ Functional closure occurs
○ When does it functionally close?
■ 72 hours after birth
○ When does it permanently close?
■ 3-4 weeks of life
■ Due to endothelial destruction, connective tissue formation, and subintimal proliferation
○ What does it transform into?
■ Ligamentum Arteriosum
○ Complications: Prematurity/Asphyxia → Closure may fail → Patent Ductus Arteriosis (PDA)
■ PDA → Abnormal blood flow → Murmur (Left sternal border/2nd intercostal space)
● Closure of the Ductus Venosus
○ What is it? Vessel connecting Umbilical Vein → Inferior vena cava, bypassing liver
○ How it closes:
■ Cord clamping: STOPS blood flow through umbilical vein
■ Pressure changes redirect blood → Liver
■ Functional closure occurs + Fibrosis converts it → Ligamentum Venosum
○ When does it functionally close?
■ 1 week after birth
○ What does it transform into?
■ Ligamentum Venosum
Structure Fetal Function Closure Trigger Functional Closure Permanent Closure
Foramen Ovale Right-to-leftshunt Increased LEFT 1-2 hours 6 months
between atria atrial pressure (Fossa Ovalis)
(bypassing lungs) (Pressure changes
between atria)
Ductus Arteriosus Right-to-left shunt Increased Lung 72 hours 3-4 weeks
from pulmonary OXYGENATION (Ligamentum
artery to aorta Arteriosum)
Ductus Venosus Bypasses LIVER → Cessation of 1 week End of Infancy
Sends blood Umbilical Vein Blood (Ligamentum
through Inferior flow Venosum)
Vena Cava (Cord Clamping →
Stops venous
return)
3
, THERMOGENIC ADAPTATION
Thermoregulation = Essential for Survival
Homeothermic : Attempt at regulating/maintaining internal core temperatures regardless of external environment
The Neutral Thermal Environment
● R/T Oxygen Consumption + Metabolism
● Neutral Thermal Environment (NTE): Temperature range where newborn can maintain their body
temperature with MINIMAL oxygen consumption + metabolic demands
○ Thermoregulation Mechanisms:
■ Vasoconstriction: Constricts blood vessels to CONSERVE heat
■ Vasodilation: Expands blood vessels to RELEASE heat
● Normal (Axillary) Temperature: 97.7 ℉ - 98.6 ℉ (Within 2-3 hours after birth)
● Decreased Adipose/Sub-Q Fat → Risk of HEAT LOSS
● Flexed Position → Reduces body surface area + CONSERVES HEAT
○ Preterm infants: Lack muscle tone for flexion → Vulnerable to HEAT LOSS
● Cold Stress: When the newborn CANNOT maintain body temperature in response to the environment
○ Causes:
■ Increased OXYGEN CONSUMPTION + Metabolic rate (MORE DEMANDS)
■ Rapid depletion of BAT
■ Potential for HYPOGLYCEMIA + HYPOXIA + METABOLIC ACIDOSIS
Physiological Adaptations for Heat Production
● To Increase Heat Production:
○ Increased Basal Metabolic Rate → Boosts energy expenditure for heat generation
○ Increased Muscle Activity → Promotes heat production through movement
○ Peripheral Vasoconstriction → Constricts blood vessels to reduce heat loss
○ Nonshivering Thermogenesis (NST): Primary Mechanism for Heat Production *
■ NEWBORNS CANNOT SHIVER
■ Trigger: Skin receptors detect → DROP in temperature → Alert SYMPATHETIC nervous
system → ACTIVATE NST
■ Process: Brown Adipose Tissue (BAT) → RAPID METABOLISM of Triglycerides → Generates
heat → Distributed to peripheral circulation (Highly vascularized brown fat cells)
■ Sites of BAT: Midscapular area, Neck/Axillae, Trachea, Esophagus, Abdominal aorta,
Kidneys, Adrenal glands
○ Brown Adipose Tissue (BAT):
■ Formation → 26-30 weeks gestation
■ Peak storage → 2-5 weeks post-birth
■ Highly vascularized + Abundant blood vessels, cells, and nerve endings
■ Efficient at metabolizing TRIGLYCERIDES → Heat Production
■ RISK: COLD STRESS → RAPIDLY depletes BAT reserves → HYPOTHERMIA
● BAT CANNOT BE RESTORED/REGENERATED
4
