Physiology of the Newborn
The neonatal or newborn
period is the first 28 days of
life during which the infant
undergoes amazing growth and
change.
Respiratory Changes :
The primary function of the respiratory system is two fold: the exchange of oxygen and carbon dioxide through
respiration and maintenance of the acid–base balance.
The amniotic fluid plays an important role in fetal lung development. Inhalation of the amniotic
fluid into the lungs helps to promote growth and differentiation of the lung tissue. Normal pulmonary functioning
is dependent on two factors: the alternating in and out fetal breathing movements and the formation of
intrapulmonary fluid.
Fetal breathing movements from11wk.
During a vaginal birth, approximately one third of the fetal lung fluid is expelled due to the “thoracic squeeze”
that occurs during passage through the birth canal. Infants of cesarean births are at a higher risk for pulmonary
transitional difficulties because they do not receive the lung compression benefits associated with a vaginal birth
Lung expansion after birth stimulates the release of surfactant, a slippery, detergent-like lipoprotein. Surfactant
causes a decreased surface tension within the alveoli, which allows for alveolar re-expansion after each
exhalation. Under normal circumstances, by the 34th to 36th weeks of gestation, surfactant is produced in
sufficient amounts to maintain alveolar stability (Bloom, 2006).
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Initiation of respiration: a
combination of physical,
sensory, thermal, and chemical
factors:
1. physical : sudden change
from intrauterine life
produces stimulations
needed to initiate
respiration.
2. Chemical :, hypercapnia
↑CO2, hypoxia ↓O2, and
acidosis ↓PH level.
3. Sensory : maximum effort is
required to expand the lungs
and full the collapsed alveoli.
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4.Thermal; The drastic change
in temperature helps to
stimulate the initiation of
respirations.
Sensors in the skin respond to the temperature changes and send signals to the respiratory system in the brain.
Physiological changes in the neonate’s temperature may occur and as long as the temperature remains within the
normal range of 36.5 to 37.0ºC
.
Several factors may interfere with the neonate’s ability to initiate respirations (prematurity,
birth asphyxia can be due to birth trauma, maternal medications, and the mode of delivery) can
interfere with normal pulmonary transition.
Neonates less that 36 weeks gestation are subject to RDS
* Normal respiration :
- Shallow, irregular in depth,
rate and rhythm.
The breathing pattern may include
brief pauses that last 5 to 15 seconds. Termed periodic breathing, this pattern is usually not associated with
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any change in skin color or heart rate and it has no prognostic significance.
- 30/40 - 60 breath \ minute
- Affected by such things like
crying.
- Accomplished mainly by the
diaphragm and abdominal
muscles.
- Dyspnea or cyanosis may
indicate anomaly or pathology.
Circulatory Changes:
As air enters the lungs, the PO2 rises in the alveoli. This normal physiologic response causes
pulmonary artery relaxation and results in a decrease in pulmonary vascular resistance. As the
pulmonary vascular resistance decreases, pulmonary blood flow increases, reaching 100% by the first
24 hours of life.
During gestation, the placenta is the organ primarily responsible for gas exchange in the fetus although
there is a small amount of blood flow to the lungs
Successful cardiopulmonary adaptation in the neonate involves five major changes: an increased
aortic pressure and decreased venous pressure; an increased systemic pressure and decreased
pulmonary pressure; and closure of the foramen ovale, the ductus arteriosus, and the ductus venosus

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 Anatomic changes :
- Umbilical arteries and vein
contract and close.
- Ductus arteriosus close
within 24/27 hours due to
increased PaO2 after
clamping the cord and lungs
start to work. Also
decreased prostaglandin E2.
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- Ductus arteriosus (34wks)and ductus venosus
(IVC & UV) are converted
to fibrous tissue
( ligaments ) within 2 3 months.
- When the pressure in the
left ventricle & atrium
exceed than that of right
atrium
Formen Ovale close.
Oxygen-rich blood returning to the
heart from the inferior vena cava crosses from the right atria to the left atria across the foramen ovale.
Foramen ovale closes functionally 1-2 hrs after delivery, physiologically by 1 month, anatomically by 6 months)
 Blood Volume : 85 - 100 ml
\ kg at birth.
The full-term infant’s average blood volume ranges from 80-90 mL/kg of body weight, as compared with a
blood volume of 90 to 105 mL/kg of body weight in the preterm infant.
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 Peripheral Circulation :
residual cyanosis in hands
and feet (Acrocyanosis).
Pulse Rate :
Immediately after birth, the newborn’s pulse rate may reach
160 to 180 beats per minute but during the first 30 minutes of life, the rate should decline to 120 to 160 beats per
minute
120 - 160 beat \ minute,
apical rate is more accurate.
 Blood Pressure : 70\40
mmhg at birth, 100\50
mmhg by the 10 day.
Blood Elements : ( Hb 16 - 22
gm ,FHb,
),
( leukocytes 15,000 - 20,000
\ ml )
HbF has a greater affi nity for oxygen than does HbA, the
newborn’s blood oxygen saturation is greater than that found in adults.
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 BloodCoaguation :
- Coagulability is temporarily
diminished because of lack
of bacteria in the intestinal
tract that contribute to the
synthesis of vitamin K.
- Coagulation time 3 – 4
minutes.
- Bleeding time 2 - 4
minutes.
- Prothrombin 50%
decreasing to 20% 30%.
- The normal newborn’s
platelet (thrombocyte)
levels range from 150,000
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to 300,000/mm3 (as in
adults). Small for
gestational age (SGA)
infants may have platelet
counts up to 25% lower
than those found in
appropriate for gestational
age neonates
.
Temperature Regulation:
The neutral thermal environment (NTE) is the range of temperature in which the newborn’s body temperature
can be maintained with minimal metabolic demands and oxygen consumption.
A term infant’s core temperature can fall by approximately 0.5ºF (0.3ºC) per minute up to a total of 5.4ºF (3ºC)
before ever leaving the birthing area. However, most term newborns are able to restore the initial decline in body
temperature and stabilize at a normal temperature of 97.7ºF (36.5ºC) to 98.6ºF (37ºC) within 2 to 3 hours after
birth
At birth temperature is as
mother one. The newborn has
poor ability regulate his body
temperature because of :
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He has little fat insulation;
.
- He has large body surface.
- He has a relatively poor
circulation.
- He doesn't yet sweat or
shiver.
- Weak muscles to maintain
flexed position.
- Their skin is thin and their
blood vessels are close to
body surface,
neonates have
less than half of the amount of subcutaneous fat normally present in adults.
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Basal Metabolism:
- Surface area of the infant is
large in comparison with
body surface.
- Basal metabolism per kg of
body is higher than that of
adult.
- Caloric requirements are
high (117 calorise \ kg
day).
Renal Funcion:
In the term newborn, the following three major physiological
factors enable the kidneys to manage bodily fluids
and excrete urine:
• The nephrons are fully functional by 34 to 36 weeks
of gestation.
• The glomerular filtration rate is lower than that of the
adult.
• There is a limited capacity for the reabsorption of
HCO3– and H_.
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- A t birth the kidney's
function 30 % - 50% of the
adult capacity and are not yet
mature enough to concentrate
urine.
- The infant usually
void within 24 hours.
- During the first 2 days of life,
infants normally void two to
six times in a 24-hour period,
with a total output of 15
mL/day.
During the first 24 to 48 hours, full-term newborns require 60 to 80 mL/kg of fluids to maintain an adequate
fluid balance. This requirement increases to 100 to 150 mL/ kg per day after the first few days, and a urine output
of 1 to 3 mL/kg per hour is indicative of adequate fluid maintenance (Hertz, 2005).
- Anurea should be
reported .
- Increase uric acid will
stain in the diaper brick dust spots.
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Hepatic Function :
- Limited because of decrease
of GIT activity and
decrease blood supply.
Decrease ability to conjugate
bilirubin will lead to jaundice.
Conjugation is a process that converts the yellow lipid-soluble (nonexcretable) bilirubin pigment
(present in bile) into a water-soluble (excretable) pigment.
Jaundice is a condition characterized by a yellow (icteric) coloration of the skin, sclera, and oral
mucous membranes. Jaundice results from the accumulation of bile pigments associated
Decrease ability to regulate
glucose will lead to
hypoglycemia.
Glucose is utilized more rapidly in the newborn than in
the fetus because of the metabolic events that occur during the normal transitional phase
-The blood glucose of a term
infant should be 70% to
80% of the maternal blood
glucose level.
-The serum blood glucose level
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drops during the first 3 hours
of life and then gradually
rises over the next 3 to 4 hours
to reach a steady state of
40 to 80 mg/dL.
- Decrease production of
prothrombin will lead to
hemorrhage.
Endocrine Function:
Disturbances are most often
related to maternally provided
hormones which can cause the
following:
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- Vaginal discharge \
bleeding in famale infant.
- Enlargement of mammary
glands in both sexes.
- Disturbance related to
maternal endocrine
pathology ( D. M )
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Physical Findings:
 Posture :
- Full term newborn assumes
symmetric posture, face
turned to side, flexed
extremities, hands tightly
fisted with thumb covered
by fingers.
- Asymmetric posture may be
caused by fracture of
clavicle or humerus or
never injury.
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● Length: 45-54/5, 46 56 cm
 Birth weight: (2.3-4.3) 2.9
- 4.1 kg
 Skin:
- Hair distribution, lanugo
hair over the back.
- Color : ( cyanosis acrocyanosis ), ( pallor cold, anemia or heart
failure)
, ( jaundice - physiologic )
- Turgor : full term should
have good skin turgor.
- Dryness feeling : sign of
post term.
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- Vernix : in skin folds.
Milia :
- enlarged sebaceous glands
on face, decreased by 2
weeks.
Mangolian spots :
small white papules or sebaceous cysts on the infant’s face that resemble
pimples
.
are areas that appear gray,
dark blue, or purple and are most commonly located on the back and buttocks, although they may also be found
the shoulders, wrists, forearms, and ankles
blue pigmentation on lower
back, decreased by 4 years.
- Petechiae : pinpoint
hemorrhage, decreased
within 24 - 48 hours.
- Edema : around eyes, face,
legs, scrotum, labia and
hands.
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 Head :
- Caput succedaneum :
swelling of soft tissue of the
scalp.
- Cephalhematoma :
subperiosteal hemorrhage .
- Molding: overlapping of
skull bones.
- Examine symmetry of facial
movement.
- Head circumference : 33 35/38 cm (2 cm larger than
chest ).
- Fontanels : ( enlarged increased intracranial
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pressure), ( sunken –
dehydration).
- Size of fontanels : (
posterior 2 – 3 months \
molding ), ( anterior 12- 18
months ).
 Face :
- Eyes : color,
hemorrhage, lid edema,
conjunctivitis, jaundice,
pupils.
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- Nose : patency and
discharge ( nasal breathing )>
- Ears : hearing,
position, cartilage.
- Mouth : size, palate,
size of the tongue, teeth,
Epstein’s pearls (
whitish hardened nodules on the
gums or roof of the mouth, may be visualized or palpated . These pearl-like inclusion cysts are not an
unusual fi nding and disappear within a few weeks
white nodules ), frenulum
linguae, oral thrust.
 Neck :
- Mobility, lymph nodes,
fractures.
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- Skin folds : increased in
trisomy 21.
- Stiffness : trauma or
infection.
● Chest :
- Circumference : 30 33 cm.
- Breast enlargment.
● Abdomen :
- protrude slightly, move with
chest in respiration.
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- Examine umbilical cord for
number of vessels, signs of
infection, umbilical hernia,
usually falls within 7 10 days.
 Genitalia:
- Female genitalia : vaginal
discharge, labia majora
cover labia minora.
- Male genitalia : testes in
scrotsl sace, examine glans
penis for urethral open
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( open ventrally hypospadias ), ( open
dorsally - epispadias)
 Back :
- Spinal column for normal
curvature and closure.
- Anal area.
 Muscloskletal:
- Extremities for fractures.
- Fingers and toes for number
( if extra digit : polydactyly)
( if fused digit : syndactyly).
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- Hips or dislocation :
clicking sounds.
* Neurologic : muscle
tone, head control and reflexes.
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Nursing Care of Newborn
In some hospitals the newborn
infant is transferred from
delivery room to transitional
nursery for intensive
observation. When stabilized
the infant Infants is admitted to
a regular nursery or mother's
room. Infants designated as
high risk are admitted to an
ICU. The immediate care of
the newborn infant after
arrived in the nursery room:
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1. Cleansing and
assessment:
- Baby's hair is frequently
matted with dried blood, the
body may have areas with a
heavy deposits of vernix
caseosa.
- Just remove the excess of
vernix and sponge away the
dried blood to delicate skin.
- General assessment beside
axillary temperature,
respiration and pulse are
measured at this time.
- Prevent undue exposure,
provide warn environment.
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2. Weighing and
measuring:
- The newborn is weighed
after arrival to nursery.
- The scales are balanced
with a protective paper on
which the naked infant is
placed.
- Great care is taken to
protect the infant from
falling of the scales.
- Accuracy is vital since is a
part of the baseline date.
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- 5% - 10% weight loss is
normal.
- After 3 – 5 days the baby
begins to gain weight and
reach their birth weight
after 2 weeks.
- Measurement of the head
and chest circumferences
and length.
3. Estimation gestational
age:
- Ability to survive is
affected by the maturity of
the infant.
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- Accurate assessment of
gestational age is vital to
effective care planning.
- Gestational age is
determined by standardized
measurements of physical
growth as : ( preterm, term,
post term), ( SGA, AGA,
LGA ).
4. Cord care:
- About 2 inches ( 5cm ) of
umbilical cord usually is
extending from the
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abdomen with some type of
clamp....
- In few days ( 7 - 10 days)
the cord shrinks and falls
off.
- Observe for signs of
hemorrhage, other clamp
may be used.
- Protect from infection.
- As a precaution against
such an infection, the area
around the umbilicus stump
is scrubbed and 70%
alcohol may be applied.
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5 .Clothing and
cover:
- It is not desirable to
constrict their movement
with heavy clothes or
blankets.
6. Positioning and
environment ;
- The baby is placed in a
preheated incubator usually
on the side with head
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slightly lower than the rest
of the body, this help
drains any remaining
amniotic fluid or mucus
from the stomach and
nasopharynx.
- Provide warm environment
24 – 27C◦.
- Never leave the infant
alone.
Extra oxygen is not
administered unless indicated
because retrolental fibroplasias
a formation of fibrous tissue behind the lens of the eye, resulting in blindness.
2 a severe form of retinopathy in premature infants associated with complete retinal detachment. It can
be prevented by timely administration of retinal laser therapy
, a condition producing
blindness may result from
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excessively high oxygen
concentration.
7. Recording and
identifying:
- All the observation,
measurements and care
given to the newborn should
be carefully recorded on the
chart.
- It is the important to label
the incubator with a clearly
marked card having the
mother's name, room
number, baby's sex, birth
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time and date and the
physician name.
- It is customary to give the
card to the mother when she
takes her baby home.
8. Feeding and rest:
- After birth the primary need
is for rest, so infant is kept
NPO for 4 – 6 hours.
- Test blood glucose, infant
may be hypoglycemia and
require feeding sooner than
usual.
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9. Discharge planning:
- The nurse takes the baby to
the mother bedside.
- The mother watches the
nurse – cut off the baby's
Id. Band and together they
check against the mother's
band.
- Give instructions about :
●
●
●
●
feeding.
Cord care.
Follow up.
Bathing, diapering.
Breast and formula
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● Measuring body
temperature.
● Recognizing
reportable signs and
symptoms " pallor, cyanosis,
vomiting, diarrhea,
abdominal respiration, fever,
hypothermia….".
- Encourage the parents to
ask questions and
participate in discussion.
-
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Complications of pregnancy
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Pregnancy is a normal funtion
of the body, not a disease
several factors can complicate
pregnancy. However including
preexisting conditions and
those that develop during
pregnancy. Pregnancy ( S )
that threaten the health of the
fetus ot the mother need
special care before, during and
after delivery.
High Risk pregnancies :
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□ Complications of
previous pregnancies:
Prolonged labor.
- Cesarean birth
-PIH
Bleeding
- Abnormal fetal position.
□
Anatomical
abnormalities:
Small pelvis.
- Incompetent cervix.
□ Metabolic and
endocrinological disorders:
Diabetes.
- Thyroid disorders.
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□ Cardiovascular
disorders:
Hypertension
- Congenital heart disease.
□ Kidney disorders:
Acute pyelonephritis.
- Acute cystitis.
□ Hemoatological
disorders:
Anemia.
- Sick cell anemia.
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□ other factors :
Age: under 16 or over 35
years.
Weight : less than 45 kg
or over 90 kg.
Syphilis.
Tuberculosis.
Smoking.
Drug addiction.
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