Module One: Physiology of Fetal/Newborn Transition Flashcards
Canalicular Period
16-26 weeks
Lumina of bronchi and terminal bronchioles become larger and the lung tissue becomes highly vascular. Respiration is possible by the end of this period but respiration system is still very immature. Canalicular period follows the Pseudoglandular Period (6-16weeks) where all the major elements of the lungs have developed except those involved in gas exchange.
Terminal Saccular Period
26w- birth: many more terminal sacs develop and epithelium becomes very thin. Blood-air barrier established for gas exchange and survival
type 1 pneumocytes: gas exchange occurs
Type 2 pneumocytes: surfactant is secreted (phospholipids & protein)
Alveolar Period
32w - 8 years : new alveoli may be added up to 8 years of age but largely complete by 3 years of age. 3 factors essential for lung development: adequate thoracic space, adequate amniotic fluid volume, fetal breathing movements.
Approximately 95% of mature alveoli develop postnatally.
mechanical event of the first breath
squeezing of thorax in the last minutes of fetal life. high pressure on the thorax as fetus passes through vagina is suddenly eliminated with birth. Fluid filling the mouth and trachea is partially released and air fills the tracheal column. The first few breaths require large amount of pressure b/c air is flowing into the fluid filled space.
biochemical event of the first breath
Relative hypoxia at the end of labor and physical stimuli which neonate is subject (cold, gravity, pain, light, noise) cause excitation of respiratory center. The response of lungs to chemoreceptors (aortic/carotid bodies) become driving force in regulation of further breaths)
Placenta
simple diffusion O2/CO2 , blood oxygen & waste product elimination, uses of 1/2 all oxygen and glucose supplied by maternal circulation for its own metabolic needs.
umbilical vein
carries oxygenated blood from placenta to the fetus
Ductus venosus
1/2 umbilical venous blood bypasses liver to ductus venosus to inferior vena cava, other 1/2 passes through the liver and enters inferior vena cava via hepatic veins.
inferior vena cava
mostly deflected across right atrium through foramen ovale into left atrium
left atrium
receive blood from righ atrium
left ventricle blood
all from inferior vena cava by way of right atrium-foramenn ovale- left atrium pathway.
superior vena cava
receives deoxygenated blood returning from brain and upper extremities, most which enters right atrium and flows to right ventricle.
Right Atrium
Mixing occurs here from deoxygenated blood from superior vena cava and oxygenated blood from inferior vena cav
right ventricle
Dominant ventricle, most blood directed away from lungs through ductus arteriosus to descending aorta then to the placenta via the umbilical arteries
Ductus arteriosus
connect pulmonary artery to descending aorta; bloods flows right to left across DA d/t high pulmonary vascular resistance and low placenta resistance.
Descending aorta
supplies kidneys, intestines, and returns blood to the placenta for oxygenation
Circulatory adjustments after birth
Cord clamping causes immediate rise in SVR (systemic vascular resistance) Lungs now become low pressure system. Increase pressure in left side heart blood flow cause foramen ovale to shut. the ductus arteriosus (which shunted oxygenated placental blood to fetal brain) closes w/in 48 hours.
understand how an infant can maintain heat and what can s/he lacks that helps to maintain body heat.
newborns create heat by shivering, voluntary muscle movements and nonshivering thermogenesis (increased metabolic rate and/or utilization of brown fat). For healthy full term infant it takes 2 days to stabilize thermoregulation
How can midwife be prepared to reduce or minimize heat loss?
pre-warm blankets, hats and clothing
dry baby immediately
replace wet blankets after drying
pre-warm newborn resuscitation area, set birth room temp 75 degrees, do not suction baby on wet birthing bed sheets, postpone bath until temp stable for 2 hours, place newborn care areas away from window, outside walls, doorways, keep newborn head covered and body well wrapped for 48 hours.
convection
loss heat from the warm body surface to cooler air current
examples : air-conditioned rooms, removal from an incubator.
radiation
losses occur when heat transfer from the heated body surface to cooler surfaces and objects not in direct contact with body.
Example: walls of an incubator.
evaporation
the loss of heat incurred when water is converted to vapor
convection
loss of heat to cooler surface by direct skin contact
example: chilled hands.
describe the ways a healthy newborn maintains his/her glucose levels, including the role of glycogen, glyconeogenesis and lipid.
fetus stores glucose as glycogen (in liver) for preparation of extrauterine life. Glucose falls for 1-2 hours after cord clamped and stabilizes at 3-4 hours, newborns maintain glucose by utilizing breast/formula milk, using glycogen stores or through creation of glucose from lipids.
glycogen
storage form of glucose in animals and humans
mainly stored in liver and muscles
glyconeogenesis
metabolic process by which organisms produce sugar (glucose) for catabolic rx from non-carbohydrate precursors. Glucose is the only energy source use by brain.
conjugation of bilirubin
extreme level of bilirubin can cause: brain damage (kernicterus or encephalopthy
symptoms: lethargy, hypotonia, poor suck , coma and seizures
describe the physiologic changes in the newborn urinary system in the first 3-4 days of life.
urine output–> term infants excrete 15-60 ml/kg micturations is 2-6x/hour in first two days.
Varney states a baby should void 4-5x daily
decreased renal blood flow and decreased GFR these can lead to fluid retention and water intoxication, newborns cannot concentrate urine well (low specific gravity). Tubular function is immature= large sodium losses. These are all corrected over the first month of life.
compare and contrast the newborn digestive system in relation to differences in babies who are breastfed vs who are given formula
it is interesting to note the increased hormonal differences between breastfed and formula fed infants. There is greater insulin response in formula fed infants. This suggests that early feeding practices may have prolonged effect on programming hormonal responses to feeding. Breastmilk empties up to twice as fast as formula. Suck swallow coordination has been demonstrated earlier in breastfeeding than in bottle fed newborns.
Maternal secretory IgA in breast milk restricts immune activation and bacteria attachment.
newborn hematocrits
43-63%
newborn hemoglobin
14-20g/dL
White blood cell range
10,000-30,000/mm3
physiologic Jaundice
incidence in full term –> 50-60%
onset : after 36 hours
peak: 3-4 days
***Asian, Asian-american peak slightly later 5-7 days breastfed
level: 5-12mg/dL (bottle)
or 7-14mg/dL breastfed & Asian
it take 1-2 weeks to get bilirubin level <3 mg/dL
Breastfeeding Associated Jaundice
incidence in full term --> 12-13% onset : 2-4 days peak: 3-6 days level >12 mg/dL ***it will take >3 week to have bili <3mg/dL
Breast milk Jaundice
incidence in full term--> 2%-4% onset: 4-7 days peak: 5-15 days bili >10mg/dL when bili is <3 is 9 weeks
Immunoglobulin A (IgA)
found high concentrations in MUCOUS MEMBRANES, particularly those lining the respiratory passages and gastrointestinal tract as well as saliva & tears
Immunoglobulin G (IgG)
most ABUNDANT type of antibody, is found in all BODY FLUIDS and protects against bacterial & viral infections
Immunoglobulin M (IgM)
mainly in BLOOD & LYMPH fluid
is the first to be made by body to fight NEW INFECTION
Immunoglobulin E (IgE)
associated with ALLERGIC RX (when immune system overreacts to environmental antigens such as pollen or pet dander). It is found in the lungs, skin, and mucous membranes.
Immunoglobulin D (IgD)
exists in minute amount in the blood, is the least understood antibody.
fetal fluid decreases several days before birth due to
increase stress hormones and increase circulating plasma proteins
Fetal circulation is characterized by what type of system
LoW
Blood flow from the placenta to the newborn stops when
newborn’s umbilical cord is clamped and cut
if the infant does not get enough oxygen the vascular pressure will
INCREASE
Increasing systemic pressure & decrease pulmonary circulation pressure causes increased circulation in the left side of the heart which leads to
closure of the foramen ovale
Decreased prostaglandin E2 is necessary for
closure of the ductus arteriosus
With the initial breath the newborn’s pulmonary vascular system
decreases
chemical influences that influence the initiation of breathing include
increased oxygen and increased carbon dioxide
pulmonary surfactant is secreted by
type II alveolar cells
fluid in the newborn’s lungs is cleared at birth by 3 routes :
(1) nose & mouth
(2) lymphatic system
(3) pulmonary veins.
infants get too cold when the fan is left on after a birth
convection
infants lose heat from not being dried properly at birth
evaporation
infant lose heat from lying on a table
conduction
Nonshivering thermogenesis is crucial to infant
thermoregulation
infants get too warm from being left under a heat lamp too long
radiation
Purpose of Bilirubin to be conjugate
–> to clear out the debris of used old and extra RBCs
the process has many steps making for potential problems.
the vast majority of newborn hematologic/liver GI systems work diligently and efficiently during the first few days.
about half of newborns do get a touch of yellow
JAUNDICE is PHYSIOLOGIC
LACK of Breastfeeding
Babies who breastfeed less than every 2-3 hours may suffer mild dehydration and lack of stools, letting the bilirubin become de-conjugated.
Breast-milk jaundice
Occurs at about age 7-10 days and results from the baby’s reaction to fatty acids of the mom’s.
this may last for weeks or months, does not cause kernicterus but can result in serious fashion crisis for pink-frilly crowd.
Neonate –> Innate Immunity
(1) skin & mucous membranes : vernix caseosum contains antimicrobrial proteins and peptides (APPs) & forms a “microbial shield: on the newborn body. The presence of vernix also moistens the skin and increases its acidity, which inhibits growth of pathogenic bacteria.
(2) sieve-like (filter) action of the respiratory passages
(3) the colonization of skin & intestine by protective microbes
(4) chemical protection offered by acidic environment of the stomach
(5) the physical barrier made by cells that line the intestinal tract.
bacteria colonization
infant begin to ingest normal bacterial flora through the diet as well as through exposure to the flora in natural environment. Breastfeeding in the month of life is powerful stimulant of innate immune response, as it influences the concentrations of innate immune cell and cytokine responses via expression of immune molecules including toll-like receptors (TLRs)
what is Morphonuclear neutrophils chemotaxis
they organized movement of phagocytic cell and opsonization (marking or cell surface of a foreign microbes or antigen to promote destruction of foreign cell **all are immature in neonate **
newborn s/sx infection can be subtle such as change in activity tone color or feeding. In addition lack of fever does not exclude the possibility of infection .
Adaptive immunity for neonate
acquired as response to specific pathogens
–> cellular response: T-cells (high level in newborn but slow respond to kill infection and aid other cells) & B-cells depends on T-cell but can activated by bacteria in early intestinal colonization by maternal intestinal bacteria.
passive immunity
by IgG from mom. The newborn is dependent on this passive immunity because significant amounts of IgG are not produced by the infant by 6 months of age
IgA & IgM are larger than IgG therefore do not cross the placenta. Identification of IgM or IgA in cord blood is an indication that fetus has actively responded to an infection while in utero
why is neonate is vulnerable to infection
because variety of deficiencies in both nature and acquired immunities, neonates response to infection is sluggish and inadequate, leading to predisposition to systemic rather than localized infections.
Vaginal birth & breast feeding both help establish healthy microbial colonization, an effect that persists throughout infants.
