WEEK 2: FOETAL AND NEONATAL PHYSIOLOGY

Question 1

The successful transition from intrauterine to extra uterine life is dependent upon significant physiologic changes that occur at birth.
These changes are successfully completed at delivery uneventfully.

However, about 10% of infants will need some intervention, and 1% will require extensive resuscitative measures at birth.

Prior to delivery, what does the human foetus depends upon for gas and nutrient exchange with the maternal circulation?

Answer 1

Prior to delivery, the human foetus depends upon the placenta for gas and nutrient exchange with the maternal circulation

Question 2

What is the goal of the right side of the heart?

Describe adult circulation on the right side of the heart.

Answer 2

Right Side of the Heart

Goal of right side: to get the blood RIGHT to the lungs so it can become oxygenated.

1. The un-oxygenated blood (this is blood that has been “used up” by your body and needs to be resupplied with oxygen) enters the heart through the SUPERIOR AND INFERIOR VENA CAVA.
2. Blood enters into the RIGHT ATRIUM
3. Then it is squeezed through the TRICUSPID VALVE
4. Blood then enters into the RIGHT VENTRICLE
5. Then it is squeezed into the PULMONIC VALVE
6. Blood is then shot up through the PULMONARY ARTERY and then enters into the lungs for some oxygen via left and right pulmonary artery

Question 3

What is the goal of the left side of the heart?

Describe adult circulation through the left side of the heart.

Answer 3

Left Side of the Heart

Goal of the left side: to get the richly, oxygenated blood that LEFT the lungs to the body to feed the brain, tissue, muscles, organs etc.)

1. Blood enters from the lungs through the PULMONARY VEIN
2. Blood then enters into the LEFT ATRIUM
3. Down through the BICUSPID VALVE (also called mitral valve)
4. Then blood is squeezed into the LEFT VENTRICLE
5. Up through the AORTIC VALVE
6. Lastly up through the AORTA, where it pumped throughout the body.

Question 4

In a nutshell, what is the function of the placenta?

Answer 4

In a nutshell, the role of the placenta is to supply the baby (from mom’s circulation) with nutrient-rich oxygenated blood and remove the build-up of waste from baby’s circulation to mom’s circulation, who will clear the build-up.

Question 5

The placenta attaches to the baby via the umbilical cord.

Name the vessels found in the umbilical cord and their functions.

Answer 5

*The umbilical cord is made up of TWO umbilical arteries that carry deoxygenated blood from the baby to the placenta,

*And ONE umbilical vein that carries oxygenated blood from the placenta to the baby.

Question 6

Shunts to Remember in Fetal Circulation

The word shunt means to “push or pull”. These shunts do just that! Two of the three shunts push blood away from the lungs, and the other one pushes blood from the liver to the inferior vena cava.

State the three shunts found in the fetal circulation and describe where they are found and their functions.

Answer 6

1. Ductus Venosus: found at the liver and umbilical vein that helps shunt oxygenated blood to the inferior vena cava.
2. Foramen Ovale: found in the wall between the right and left atrium that allows oxygenated blood from the right atrium to flow into the left atrium (hence shunting blood AWAY from the lungs so it won’t go in the right ventricle then to the pulmonary artery).
3. Ductus Arteriosus: found connecting the pulmonary artery and aorta.

-It helps shunt mixed (oxygenate and deoxygenated) blood away from the lungs…instead it flows directly into the aorta (specifically to the descending aorta) where it will eventually travel to the umbilical arteries and back to the placenta.

Question 7

Name the vessel that connects the descending aorta to the umbilical artery.

Answer 7

Internal iliac artery

Question 8

Why does blood from the right side of the heart able to be shunted to the left side of the heart?

Answer 8

Remember that the baby’s doesn’t breathe yet.

The resistance in the lungs is HIGH due to being filled with fluid.

The high resistance creates a higher pressure on the right side of the heart compared to the left, which helps play a role with shunting blood away from the lungs.

Remember that blood from a higher resistance easily flows to a lower resistance.

NOTE: this resistance changes after birth once the baby starts breathing and is responsible for closing off some of the shunts

Question 9

Describe the Fetal Circulation BEFORE Birth.

Answer 9

1. The placenta pulls nutrient-rich oxygenated blood from mom’s circulation to the UMBILICAL VEIN.
2. This blood flows down to the liver where some will go to the liver’s circulation through the hepatic portal vein (the liver is NOT fully functional yet), but most will be SHUNTED by the DUCTUS VENOSUS to the INFERIOR VENA CAVA (IVC).

-Therefore, rich oxygenated blood enters the IVC. Note: the IVC is also draining back deoxygenated blood just like it does in “normal” heart circulation as described at the beginning of this review.

3. The blood from the IVC enters into the RIGHT ATRIUM.

*Majority of this oxygenated blood will be SHUNTED through the FORAMEN OVALE (note: some of oxygenated blood will go down into the right ventricle).

*Majority of the oxygenated blood needs to get to the body…there is no need for it to go through the rest of the right side of the heart because the lungs are NOT functioning yet.

*So, this oxygenated blood flows from the RIGHT ATRIUM to the LEFT ATRIUM, down in the LEFT VENTRICLE, up through the aorta, and to the rest of the body.

Also, draining into the right atrium is deoxygenated blood from the SUPERIOR VENA CAVA (SVC) and IVC.

4. This deoxygenated blood along with some of the oxygenated blood from the umbilical vein will flow down into the RIGHT VENTRICLE. The blood is now mixed (contains oxygenated and deoxygenated blood).
5. The mixed blood flows up through the PULMONARY ARTERY and is SHUNTED from the pulmonary artery to the AORTA (specifically the descending aorta) via the DUCTUS ARTERIOSUS.

This blood flows down through the descending aorta. The descending aorta branches off into many arteries. Some of this blood will go to lower extremities and some will go via the internal iliac arteries.

6. At the internal iliac arteries, the blood will flow into the UMBILICAL ARTERIES where it will leave the baby and go back to the placenta.

Mom’s circulation will clear the build-up of waste and re-supply it will fresh oxygen and nutrients.

7. This cycle continues over and over!

Question 10

Describe Fetal Circulation AFTER Birth

Answer 10

When the baby is born, the umbilical cord is clamped off, and it starts breathing, the shunts begin to close or seal off.

They are NO LONGER needed because the placenta is now non-functional, while the lungs are now functioning.

When the umbilical cord is clamped this stops blood flow through the umbilical vein.

Therefore, the ductus venous is no longer needed and it seals off. Oxygenated blood will NOT enter into the IVC.

Question 11

1. What structures in fetal circulation play a role in shunting blood away from the LUNGS? Select all that apply:*
   A. Ductus arteriosus
   B. Ductus venosus
   C. Umbilical artery
   D. Foramen ovale
   E. Umbilical vein

Answer 11

The answers are A and D. The ductus arteriosus and foramen ovale are the structures that help blood flow bypass (or shunt) away from the lungs. These structures seal off and become nonfunctional after birth. The ductus venosus plays a role with shunting blood from the LIVER (not lungs).

Question 12

2. Select the structures in fetal circulation that play a role with shunting blood away from the lungs and liver? Select all that apply:*
   A. Umbilical vein
   B. Ductus venosus
   C. Foramen ovale
   D. Umbilical artery
   E. Ductus arteriosus

Answer 12

The answers are B, C, and E. These structures play a role with shunting blood from the lungs and liver. The ductus venosus shunts some blood from the LIVER, and the foramen ovale and ductus arteriosus shunt blood from the LUNGS.

Question 13

3. Which statement below accurately describes the role of the ductus arteriosus?*
   A. “The ductus arteriosus helps connect the umbilical artery to the inferior vena cava.”
   B. “The ductus arteriosus is found between the right and left atrium.”
   C. “In fetal circulation the pulmonary artery and aorta are connected via the ductus arteriosus.”
   D. “The ductus arteriosus only carries oxygenated blood from the left side of the heart to the right side.”

Answer 13

The answer is C. This is the only correct statement about the ductus arteriosus. This structure connects the pulmonary artery and aorta, which helps carry mixed blood (oxygenated and deoxygenated blood) to the lower body and back to the placenta via the umbilical arteries (which branch off the descending aorta). This structure helps shunt blood away from the lungs.

Question 14

4. Fill in the blank: The ______________ carries oxygenated blood from the placenta to the fetus. Some of the blood flow from this structure is shunted from the __________ to the ___________ via the _______________.*
   A. umbilical artery, lungs, aorta, ductus arteriosus
   B. umbilical vein, liver, inferior vena cava, ductus venosus
   C. umbilical vein, liver, superior vena cava, ductus arteriosus
   D. umbilical artery, liver, inferior vena cava, ductus venosus

Answer 14

The answer is B. The UMBILICAL VEIN carries oxygenated blood from the placenta to the fetus. Some of the blood flow from this structure is shunted from the LIVER to the INFERIOR VENA CAVA via the DUCTUS VENOSUS.

Question 15

5. Fill in the blank: The pressure in the fetal lungs before birth is __________, which allows blood from the _____________ to shunt into the ______________ via the __________________.*
   A. high, pulmonary artery, aorta, ductus arteriosus
   B. high, pulmonary vein, aorta, ductus venosus
   C. low, aorta, pulmonary artery, pulmonary vein, ductus arteriosus
   D. low, right atrium, left atrium, foramen ovale

Answer 15

The answer is A. The pressure in the fetal lungs is HIGH, which allows blood from the PULMONARY ARTERY to shunt into the AORTA via the DUCTUS ARTERIOSUS.

Question 16

6. Fill in the blank: In the fetus’ circulation before birth the pressure is ____________ on the right side of the heart compared to the left side. This causes some of the blood from the _________ atrium to flow into the __________ atrium via the ______________.*
   A. lower, right, left, foramen ovale
   B. higher, left, right, ductus arteriosus
   C. higher, right, left, foramen ovale
   D. lower, left, right, ductus venosus

Answer 16

The answer is C. In the fetus before birth, the pressure in HIGHER on the right side of the heart compared to the left side. This causes the blood from the RIGHT atrium to flow into the LEFT atrium via the FORAMEN OVALE.

Question 17

7. True or False: The umbilical cord is made up of two umbilical veins and one umbilical artery.*
   True
   False

Answer 17

The answer is FALSE: The statement should say: The umbilical cord is made up of ONE (not two) umbilical vein and TWO (not one) umbilical arteries.

Question 18

8. After the birth of the baby, heart circulation changes due to the closure of the shunting structures in the baby’s circulatory system. Select below all the reasons for the closure of these shunting structures:*
   A. The pressure in the right side of the heart decreases compared to the left side.
   B. The resistance in the lungs decreases.
   C. Prostaglandin production increases.
   D. Oxygen levels in the baby’s body increase.

Answer 18

The answers are: A, B, and D. The only incorrect statement is Option C. The placenta produces prostaglandins. When it is removed the production of prostaglandin production decreases, which causes the ductus arteriosus to close.

Question 19

9. Fill in the blank: In fetal circulation the umbilical artery carries _____________, while the umbilical vein carries ________________.*
   A. deoxygenated blood, oxygenated blood.
   B. deoxygenated/oxygenated blood, oxygen blood.
   C. oxygenated blood, deoxygenated blood.

Answer 19

The answer is A. The umbilical artery in fetal circulation carries DEOXYGENATED, while the umbilical vein carries OXYGENATED.

Question 20

10. The right ventricle pumps what type of blood up through the pulmonary artery?*
    A. Oxygenated
    B. Deoxygenated
    C. Mixed

Answer 20

The answer is C. The blood pumped from the right ventricle contains both oxygenated and deoxygenated blood. Therefore, it is mixed.

Question 21

The intrauterine oxygen tension is low compared with that seen in extra uterine life.

What is the highest oxygenated foetal blood is found in the umbilical vein PO2?

Oxygen saturation decreases when mixed with venous return, so that blood returning to the placenta will have a PO2 ________.

Answer 21

The intrauterine oxygen tension is low compared with that seen in extra uterine life. The highest oxygenated foetal blood is found in the umbilical vein with PO2 as high as 55 ± 7 mmHg

Oxygen saturation decreases when mixed with venous return, so that blood returning to the placenta will have a PO2 of 15 to 25 mmHg

Question 22

Despite the low oxygen tension in the foetus, there is adequate tissue oxygenation because of the following factors.

State the factors contributing to that.

Answer 22

*Foetal hemoglobin
*Decreased foetal oxygen consumption
*The foetus does not need to maintain thermoregulation
*In the foetus, many physiologic functions are reduced,
*Differential blood flow
*Brain, liver and kidneys get the lion’s share

-The phrase “Brain, liver, and kidneys get the lion’s share” is a simple and figurative way of expressing that these three organs receive a significant portion of the body’s resources, nutrients, and blood flow because of their critical functions.

Question 23

Neonate must rapidly make physiologic changes in cardiopulmonary function.

Outline feature that characterizes a successful transition.

Answer 23

*Alveolar fluid clearance
*Lung expansion
*Circulatory changes with increases in pulmonary perfusion and systemic pressure, and
*Closure of the right-to-left shunts of the foetal circulation

Question 24

During gestation, fetal lung development is a complex and highly regulated process.

One of the mechanisms that plays a significant role in promoting lung growth and development during gestation is chloride-driven liquid secretion.

GIVE an explanation of how this process works and its importance.

Answer 24

1. Chloride-Driven Liquid Secretion:

The fetal lungs are filled with a fluid known as fetal lung liquid, which is crucial for lung development.

Chloride-driven liquid secretion refers to the movement of chloride ions across the cells that line the developing lung tissues.

This movement of chloride ions is typically accompanied by the movement of sodium ions, which helps to create an osmotic gradient.

2. Osmotic Gradient:

The movement of chloride and sodium ions into the developing lung tissues generates an osmotic gradient.

This osmotic gradient encourages the movement of water from the surrounding tissues into the fetal lung spaces.

As a result, the fetal lungs become filled with this liquid, creating a microenvironment that supports proper lung growth and development.

3. Lung Expansion and Stretching:

The influx of liquid into the fetal lungs leads to lung expansion and stretching.

This stretching is a crucial mechanical signal that promotes the growth and development of the lung tissue.

It helps the lungs achieve the necessary structural changes and increases the surface area available for gas exchange.

4. Surfactant Production:

As the fetal lungs expand and mature, they also begin to produce a substance called surfactant.

Surfactant is a complex mixture of lipids and proteins that lowers surface tension in the alveoli (small air sacs in the lungs) and prevents them from collapsing during exhalation.

This is essential for efficient breathing and gas exchange after birth.

IMPORTANCE

*Critical for Respiratory Function:

The chloride-driven liquid secretion and subsequent lung expansion are critical for the development of the respiratory system.

This process ensures that the lungs are prepared to function effectively once the baby is born and begins breathing air.

Proper lung development is crucial for the baby’s ability to exchange oxygen and carbon dioxide, which is essential for life.

Question 25

Describe how the fetal lungs prepare for normal function during late gestation.

Answer 25

1. Hormonal Changes (Late Gestation): As the fetus nears the end of gestation, the concentration of hormones, including catecholamines, changes. These hormonal changes, along with mechanical signals, play a crucial role in signaling the fetal lung to undergo a transition in its function. 2. Switch to Sodium Resorption: In response to increased concentrations of catecholamines and other hormonal signals, the lung epithelium switches its function. Instead of actively secreting chloride and liquid into the air spaces, it begins actively resorbing sodium and liquid from the air spaces. This process results in the removal of fluid from the lung, gradually decreasing the fluid-filled environment that was essential for lung development in early gestation. 3. Preparation for Air Breathing: The switch from chloride secretion to sodium resorption prepares the fetal lungs for the transition to air breathing at birth. By reducing the fluid content in the air spaces and increasing the absorption of sodium, the lungs create a microenvironment that supports the onset of breathing. This change helps prevent the aspiration of liquid into the airways during the baby's first breaths. 4. Surfactant Production and Alveolar Maturation: As fluid is resorbed, the lung's alveoli (small air sacs) become more stable and less prone to collapse. Additionally, the shift in the lung's function contributes to the production of surfactant, a substance that reduces surface tension in the alveoli, ensuring their stability during breathing.

Question 26

Describe how the following come about. 1. "The initial effective breaths of the neonate generate high transpulmonary pressures": 2. "The initial negative hydrostatic pressure drives alveolar fluid from the air spaces into the interstitium and subsequently the pulmonary vasculature":

Answer 26

1. "The initial effective breaths of the neonate generate high transpulmonary pressures": When a neonate takes its first breaths after birth, the act of inflating the lungs generates high transpulmonary pressures. This means there is a significant difference in pressure between the inside of the lungs and the surrounding chest cavity. These high transpulmonary pressures are necessary to expand the alveoli (small air sacs in the lungs) and establish functional ventilation. Increasing inspiratory pressure expands the alveolar air spaces and establishes functional residual capacity (FRC) . Lung expansion also stimulates surfactant release, which reduces alveolar surface tension, increases compliance, and stabilizes the FRC. 2. "The initial negative hydrostatic pressure drives alveolar fluid from the air spaces into the interstitium and subsequently the pulmonary vasculature": In the fetal lung, the air spaces are filled with fluid necessary for lung growth and development. However, during birth and the initial breaths, the neonate's respiratory efforts create a negative pressure gradient within the alveoli. This negative pressure, in combination with the high transpulmonary pressures, plays a critical role in driving alveolar fluid out of the air spaces. As the alveolar fluid is driven from the air spaces, it moves into the interstitium (the connective tissue within the lung) and subsequently into the pulmonary vasculature. This process helps to clear the alveoli of fluid, making way for the exchange of gases (oxygen and carbon dioxide) and establishing effective respiration.

Question 27

Thoracic squeeze is only a minor contributor to alveolar fluid clearance. What is thoracic squeeze?

Answer 27

"Thoracic squeeze" refers to the pressure exerted on the chest or thoracic region of the infant during the process of childbirth. While it may have some effect on clearing alveolar fluid, it is indeed considered a minor contributor to the overall process of alveolar fluid clearance in the newborn.

Question 28

Outline MATERNAL CONDITIONS risk factors associated with a greater likelihood of having difficulty making a successful transition of the lungs and of requiring resuscitation.

Answer 28

*Advanced maternal age, *Maternal diabetes mellitus or hypertension, substance abuse, *Previous history of stillbirth, foetal loss, or early neonatal death

Question 29

Outline THE 10 Foetal/Antenatal CONDITIONS risk factors associated with a greater likelihood of having difficulty making a successful transition of the lungs and of requiring resuscitation.

Answer 29

1. Prematurity 2. Post maturity 3. Congenital anomalies 4. Multiple gestation 5. Antepartum complications − Placental anomalies (e.g., placenta previa), or either oligo hydramnios or poly hydramnios) 6. Transverse lie or breech presentation, 7. Chorioamnionitis, foul-smelling or meconium-stained amniotic fluid, 8. Antenatal asphyxia: refers to a condition in which a fetus (unborn baby) experiences a lack of oxygen (hypoxia) during the antenatal period, which encompasses the time from conception to the moment of birth. 9. Maternal administration of a narcotic 10. Delivery that requires instrumentation

Question 30

DEFINE oligohydramnios AND polyhydramnios.

Answer 30

Oligohydramnios is a condition characterized by an abnormally low volume of amniotic fluid in the amniotic sac during pregnancy. Polyhydramnios is the opposite of oligohydramnios and is characterized by an abnormally high volume of amniotic fluid in the amniotic sac during pregnancy.

Question 31

Outline Neonatal difficulties at birth.

Answer 31

*Lack of respiratory effort *Blockage of the airways *Impaired lung function *Persistent increased pulmonary vascular resistance (also referred to as persistent pulmonary hypertension or persistent foetal circulation) *Abnormal cardiac structure and/or function

Question 32

Persistent pulmonary hypertension of the newborn (PPHN)

Answer 32

Pulmonary vascular resistance (PVR) remains abnormally elevated after birth. It results from blood shunting right to left through foetal circulatory pathways via the ductus arteriosus and foramen ovale, Result in severe life-threatening hypoxemia and hypercapnia that may not respond to conventional respiratory support. *Hypoxemia is a medical term that refers to an abnormally low level of oxygen in the arterial blood. *Hypercapnia is a medical condition characterized by an excessive level of carbon dioxide (CO2) in the bloodstream.

Question 33

Infants with severe congenital heart disease may have difficulty with the transition to extra uterine life. State the congenital anomalies of the heart formation.

Answer 33

cyanotic heart disease *Those with severe pulmonary oedema due to increased pulmonary arterial blood flow or impaired left ventricular function. 1. Ventricular Septal Defect (VSD): This is a hole in the septum (wall) that separates the two lower chambers of the heart (ventricles). It allows oxygen-rich and oxygen-poor blood to mix. 2. Atrial Septal Defect (ASD): An ASD is a hole in the septum that separates the two upper chambers of the heart (atria). It allows blood to flow between the atria, which can lead to increased blood flow to the lungs. 3. Tetralogy of Fallot: This complex heart defect consists of four abnormalities: *A ventricular septal defect, *Pulmonary stenosis (narrowing of the pulmonary valve or artery), *An overriding aorta (the aorta is shifted over the ventricular septal defect), *Right ventricular hypertrophy (thickening of the right ventricular muscle). 4. Coarctation of the Aorta: In this condition, the aorta, the main artery that carries oxygen-rich blood from the heart to the body, is narrowed or constricted, which can reduce blood flow to the lower part of the body. *Transposition of the Great Arteries: In this defect, the aorta and pulmonary artery are switched, meaning the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. This results in two separate circulatory loops that do not mix oxygen-poor and oxygen-rich blood as they should. 5. Hypoplastic Left Heart Syndrome (HLHS): This is a complex heart defect in which the left side of the heart (left ventricle and aorta) is underdeveloped, making it unable to pump blood effectively. This condition typically requires a series of surgeries to redirect blood flow and improve heart function. 7. Double Outlet Right Ventricle (DORV): In DORV, both the pulmonary artery and aorta originate from the right ventricle, which can lead to mixing of oxygen-poor and oxygen-rich blood. 8. Truncus Arteriosus: This condition occurs when there is a single large blood vessel (truncus arteriosus) that should have separated into the aorta and pulmonary artery. It can result in mixing of oxygen-poor and oxygen-rich blood. 9. Pulmonary Atresia: In this defect, the pulmonary valve does not form properly, which can obstruct blood flow to the lungs. 10. An aorticopulmonary fistula is a rare medical condition characterized by an abnormal connection, or fistula, between the aorta (the main artery that carries oxygenated blood from the heart to the body) and the pulmonary artery (the blood vessel that carries blood to the lungs). This abnormal connection allows blood to flow from the aorta, which contains oxygenated blood, into the pulmonary artery, which carries deoxygenated blood to the lungs. As a result, oxygenated blood mixes with deoxygenated blood, which can lead to reduced oxygen delivery to the body's tissues.

Question 34

Describe the following congenital anomalies of the heart. Patent Ductus Arteriosus (PDA): Ebstein's Anomaly: Pulmonary Stenosis: Aortic Stenosis: Hypoplastic Right Heart Syndrome (HRHS): Total Anomalous Pulmonary Venous Connection (TAPVC): Double Inlet Left Ventricle (DILV): Tricuspid Atresia:

Answer 34

Patent Ductus Arteriosus (PDA): PDA is a condition where the ductus arteriosus, a fetal blood vessel that normally closes shortly after birth, remains open. This can lead to abnormal blood flow between the aorta and pulmonary artery. Ebstein's Anomaly: This rare condition affects the tricuspid valve, which separates the right atrium from the right ventricle. In Ebstein's anomaly, the tricuspid valve is abnormally formed and may not function properly. Pulmonary Stenosis: Pulmonary stenosis is a narrowing of the pulmonary valve or artery, which can restrict blood flow from the right ventricle to the lungs. Aortic Stenosis: Aortic stenosis involves a narrowing of the aortic valve, which can impede the flow of oxygen-rich blood from the left ventricle to the aorta. Hypoplastic Right Heart Syndrome (HRHS): HRHS is the opposite of hypoplastic left heart syndrome, where the right side of the heart (right ventricle and pulmonary artery) is underdeveloped. Total Anomalous Pulmonary Venous Connection (TAPVC): In TAPVC, the pulmonary veins do not connect to the left atrium as they should. Instead, they connect to another location, often the right atrium, leading to abnormal blood flow. Double Inlet Left Ventricle (DILV): DILV is a rare condition where both the atrioventricular valves connect to the left ventricle, and the right ventricle is either underdeveloped or absent. Tricuspid Atresia: Tricuspid atresia is a condition where the tricuspid valve is absent or abnormally developed, leading to poor blood flow between the right atrium and right ventricle.

Question 35

In how many % of infants are the extra uterine changes successfully completed at delivery without requiring any special assistance? What is the approximately % of neonates having some difficulty and require resuscitative efforts at birth?

Answer 35

The successful transition from intrauterine to extra uterine life is dependent upon significant physiologic changes that occur at birth. In almost all infants (90 %), these changes are successfully completed at delivery without requiring any special assistance. Approximately ten % of neonates have some difficulty and require resuscitative efforts at birth. Infants who are more likely to require resuscitation can be identified by maternal and neonatal risk factors, and the presence of antepartum and delivery room complications.