Newborn Physiological Adaptations

• The newborn period extends from birth through the first 28 days of life
• This period involves the newborn's adaptation to extrauterine life
• Nurses play a key role in assessing and supporting this adaptation

Physiological Adaptations

• The most critical extrauterine adjustments are respiratory and circulatory
• Other systems also undergo significant changes

Respiratory System

• Initiation of breathing is crucial
• Fetal lung development includes practice breathing movements
• During labor, lung fluid production decreases, and absorption into lung tissues increases
• Normal newborn respiration rate is 30 to 60 breaths per minute
• Breathing is primarily diaphragmatic but shallows and irregular
• Brief periods of apnea (less than 15 seconds) are normal
• Signs of respiratory distress include nasal flaring, intercostal or xiphoid retractions, grunting, and seesaw respirations
• Acrocyanosis (cyanosis of hands and feet) is normal in the first 24 hours
• Central cyanosis is always abnormal
• The foramen ovale, ductus arteriosus, and ductus venosus close after birth
• These closures lead to increased pulmonary blood flow and systemic blood pressure
• The foramen ovale functionally closes due to increased pressure in the left atrium
• The ductus arteriosus constricts due to increased oxygen levels and decreased prostaglandins
• The ductus venosus closes due to cessation of umbilical venous return
• Heart rate is initially rapid (160-180 bpm) but stabilizes to 110-160 bpm
• Blood pressure averages 60-80/40-50 mm Hg at birth
• Blood volume varies from 80-100 mL/kg
• Leukocytosis is normal initially
• Platelet count and clotting factors are normal
• Thermoregulation is crucial for newborn survival
• Newborns are prone to heat loss due to a large surface area-to-body mass ratio
• Mechanisms of heat loss include conduction, convection, evaporation, and radiation
• Conduction is heat loss to a cooler surface via direct contact
• Convection is heat loss to cooler air currents
• Evaporation is heat loss when moisture vaporizes from the skin
• Radiation is heat loss to cooler objects not in direct contact with the newborn
• Thermogenesis occurs through increased metabolic rate, muscular activity, and nonshivering thermogenesis
• Nonshivering thermogenesis involves the metabolism of brown fat
• Brown fat is a specialized tissue found in newborns
• Cold stress increases oxygen consumption and can lead to respiratory distress and hypoglycemia
• Overheating can cause tachycardia, increased metabolic rate, and dehydration
• Glucose is the primary energy source for newborns
• Glucose levels stabilize at 50-60 mg/dL in the first few hours
• Hypoglycemia (glucose <40 mg/dL) can cause jitteriness, poor feeding, and seizures
• Early feeding helps stabilize glucose levels
• Bilirubin is a byproduct of red blood cell breakdown
• The liver conjugates bilirubin, making it water-soluble for excretion
• Newborns have a higher bilirubin production rate than adults
• Jaundice (hyperbilirubinemia) is common in newborns
• Physiologic jaundice occurs after the first 24 hours
• Pathologic jaundice occurs within the first 24 hours and requires intervention
• Breastfeeding jaundice can occur in the first week due to inadequate milk intake
• Breast milk jaundice occurs later due to factors in breast milk that increase bilirubin reabsorption.
• The stomach capacity is small (5-10 mL initially)
• Gastric emptying is influenced by volume and composition of feeding
• Meconium is the first stool, usually passed within 24-48 hours
• Stools transition from meconium to transitional stools to milk stools
• Breastfed infants have more frequent, seedy, yellow stools
• Formula-fed infants have fewer, pastier, pale yellow stools
• Newborns have limited ability to concentrate urine
• The first void should occur within 24 hours
• Uric acid crystals may cause a reddish stain in the diaper
• IgG crosses the placenta providing passive immunity
• IgM is produced by the newborn in response to infection
• IgA is obtained through breast milk
• Newborns should receive vaccines according to the recommended schedule

Behavioral Adaptations

• Newborns exhibit predictable behavioral patterns
• These patterns include periods of reactivity and sleep

Periods of Reactivity

• The first period of reactivity lasts up to 30 minutes after birth
• The newborn is alert, active, and responsive
• Heart rate and respiratory rate are elevated
• The sleep period follows, lasting from a few minutes to 2-4 hours
• The newborn is quiet and sleeps
• Heart rate and respiratory rate decrease
• The second period of reactivity occurs 2-8 hours after birth
• The newborn is again alert and responsive
• Meconium may be passed
• Physiological responses such as increased heart rate and respiratory rate, and mucus production can occur

Sleep-Wake States

• Deep sleep: Quiet, regular breathing, minimal movement
• Light sleep: More active, irregular breathing, REM may be observed
• Drowsy: Variable activity and responsiveness
• Quiet alert: Attentive and responsive
• Active alert: Fussy, easily stimulated
• Crying: Intense motor activity and unresponsiveness

Sensory Capacities

• Vision is clearest at 8-12 inches
• Newborns prefer faces and contrasting patterns
• Hearing is acute; newborns respond to noises
• Smell: Newborns can distinguish their mother's scent
• Taste: Newborns prefer sweet tastes
• Touch: Sensitive to pain and touch

Response to Environmental Stimuli

• Temperament varies among newborns
• Habituation is the ability to block out repetitive stimuli
• Consolability is the ability to self-soothe or be soothed
• Newborns exhibit motor skills such as grasping, sucking, and rooting
• The rooting reflex helps the newborn find the nipple
• The sucking reflex allows the newborn to feed
• The Moro reflex (startle reflex) is a response to sudden stimuli
• The Babinski reflex is the fanning of toes when the sole of the foot is stroked