Module One: Physiology of Fetal/Newborn Transition

Question 1

Canalicular Period

Answer 1

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.

Question 2

Terminal Saccular Period

Answer 2

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)

Question 3

Alveolar Period

Answer 3

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.

Question 4

mechanical event of the first breath

Answer 4

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.

Question 5

biochemical event of the first breath

Answer 5

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)

Question 6

Placenta

Answer 6

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.

Question 7

umbilical vein

Answer 7

carries oxygenated blood from placenta to the fetus

Question 8

Ductus venosus

Answer 8

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.

Question 9

inferior vena cava

Answer 9

mostly deflected across right atrium through foramen ovale into left atrium

Question 10

left atrium

Answer 10

receive blood from righ atrium

Question 11

left ventricle blood

Answer 11

all from inferior vena cava by way of right atrium-foramenn ovale- left atrium pathway.

Question 12

superior vena cava

Answer 12

receives deoxygenated blood returning from brain and upper extremities, most which enters right atrium and flows to right ventricle.

Question 13

Right Atrium

Answer 13

Mixing occurs here from deoxygenated blood from superior vena cava and oxygenated blood from inferior vena cav

Question 14

right ventricle

Answer 14

Dominant ventricle, most blood directed away from lungs through ductus arteriosus to descending aorta then to the placenta via the umbilical arteries

Question 15

Ductus arteriosus

Answer 15

connect pulmonary artery to descending aorta; bloods flows right to left across DA d/t high pulmonary vascular resistance and low placenta resistance.

Question 16

Descending aorta

Answer 16

supplies kidneys, intestines, and returns blood to the placenta for oxygenation

Question 17

Circulatory adjustments after birth

Answer 17

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.

Question 18

understand how an infant can maintain heat and what can s/he lacks that helps to maintain body heat.

Answer 18

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

Question 19

How can midwife be prepared to reduce or minimize heat loss?

Answer 19

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.

Question 20

convection

Answer 20

loss heat from the warm body surface to cooler air current

examples : air-conditioned rooms, removal from an incubator.

Question 21

radiation

Answer 21

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.

Question 22

evaporation

Answer 22

the loss of heat incurred when water is converted to vapor

Question 23

convection

Answer 23

loss of heat to cooler surface by direct skin contact

example: chilled hands.

Question 24

describe the ways a healthy newborn maintains his/her glucose levels, including the role of glycogen, glyconeogenesis and lipid.

Answer 24

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.

Question 25

glycogen

Answer 25

storage form of glucose in animals and humans

mainly stored in liver and muscles

Question 26

glyconeogenesis

Answer 26

metabolic process by which organisms produce sugar (glucose) for catabolic rx from non-carbohydrate precursors. Glucose is the only energy source use by brain.

Question 27

conjugation of bilirubin

Answer 27

extreme level of bilirubin can cause: brain damage (kernicterus or encephalopthy
symptoms: lethargy, hypotonia, poor suck , coma and seizures

Question 28

describe the physiologic changes in the newborn urinary system in the first 3-4 days of life.

Answer 28

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.

Question 29

compare and contrast the newborn digestive system in relation to differences in babies who are breastfed vs who are given formula

Answer 29

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.

Question 30

newborn hematocrits

Answer 30

43-63%

Question 31

newborn hemoglobin

Answer 31

14-20g/dL

Question 32

White blood cell range

Answer 32

10,000-30,000/mm3

Question 33

physiologic Jaundice

Answer 33

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

Question 34

Breastfeeding Associated Jaundice

Answer 34

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

Question 35

Breast milk Jaundice

Answer 35

incidence in full term--> 2%-4% 
onset: 4-7 days 
peak: 5-15 days
bili >10mg/dL 
when bili is <3 is 9 weeks

Question 36

Immunoglobulin A (IgA)

Answer 36

found high concentrations in MUCOUS MEMBRANES, particularly those lining the respiratory passages and gastrointestinal tract as well as saliva & tears

Question 37

Immunoglobulin G (IgG)

Answer 37

most ABUNDANT type of antibody, is found in all BODY FLUIDS and protects against bacterial & viral infections

Question 38

Immunoglobulin M (IgM)

Answer 38

mainly in BLOOD & LYMPH fluid

is the first to be made by body to fight NEW INFECTION

Question 39

Immunoglobulin E (IgE)

Answer 39

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.

Question 40

Immunoglobulin D (IgD)

Answer 40

exists in minute amount in the blood, is the least understood antibody.

Question 41

fetal fluid decreases several days before birth due to

Answer 41

increase stress hormones and increase circulating plasma proteins

Question 42

Fetal circulation is characterized by what type of system

Answer 42

LoW

Question 43

Blood flow from the placenta to the newborn stops when

Answer 43

newborn’s umbilical cord is clamped and cut

Question 44

if the infant does not get enough oxygen the vascular pressure will

Answer 44

INCREASE

Question 45

Increasing systemic pressure & decrease pulmonary circulation pressure causes increased circulation in the left side of the heart which leads to

Answer 45

closure of the foramen ovale

Question 46

Decreased prostaglandin E2 is necessary for

Answer 46

closure of the ductus arteriosus

Question 47

With the initial breath the newborn’s pulmonary vascular system

Answer 47

decreases

Question 48

chemical influences that influence the initiation of breathing include

Answer 48

increased oxygen and increased carbon dioxide

Question 49

pulmonary surfactant is secreted by

Answer 49

type II alveolar cells

Question 50

fluid in the newborn’s lungs is cleared at birth by 3 routes :

Answer 50

(1) nose & mouth
(2) lymphatic system
(3) pulmonary veins.

Question 51

infants get too cold when the fan is left on after a birth

Answer 51

convection

Question 52

infants lose heat from not being dried properly at birth

Answer 52

evaporation

Question 53

infant lose heat from lying on a table

Answer 53

conduction

Question 54

Nonshivering thermogenesis is crucial to infant

Answer 54

thermoregulation

Question 55

infants get too warm from being left under a heat lamp too long

Answer 55

radiation

Question 56

Purpose of Bilirubin to be conjugate

Answer 56

–> 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

Question 57

LACK of Breastfeeding

Answer 57

Babies who breastfeed less than every 2-3 hours may suffer mild dehydration and lack of stools, letting the bilirubin become de-conjugated.

Question 58

Breast-milk jaundice

Answer 58

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.

Question 59

Neonate –> Innate Immunity

Answer 59

(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.

Question 60

bacteria colonization

Answer 60

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)

Question 61

what is Morphonuclear neutrophils chemotaxis

Answer 61

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 .

Question 62

Adaptive immunity for neonate

Answer 62

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.

Question 63

passive immunity

Answer 63

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

Question 64

why is neonate is vulnerable to infection

Answer 64

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.