Fetal to Neonatal Transition

Question 1

What are the 3 phase of fetal to neonatal transitioning?

Answer 1

1. Late gestation
2. Parturition
3. establishing independent homeostatic regulation after separation from the placenta

Question 2

What happens to cortisol levels in the last 5 weeks of gestation?

Answer 2

increased cortisol contributing to lung maturation and surfactant production

Question 3

What factors play a huge role in the final steps of parturition?

Answer 3

Prostaglandin F2 and Placental corticotropin-releasing factor that stimulates paracrine production of prostanoids from the fetal placental membranes to induce parturition.

Question 4

What does the foramen ovale, ductus venous, and ductus arteriosus bypass?

Answer 4

Foramen ovale: R atrum to L atrium
Ductus venosus: umbilical vein to IVC bypassing the liver
Ductus arteriosus: bypasses the lung from pulm artery to descending aorta

Question 5

What carries oxygenated blood from the parent to the fetus?

Answer 5

umbilical vein

Question 6

How are nutrients transferred from the mother to the placenta?

Answer 6

glucose: carrier mediated diffusion
Proteins: rapid, slow and de novo synthesis
Fat: gradient dependent diffusion

Question 7

What maintains an open ductus arteriosus, inhibits brown fat thermogenesis, and inhibits fetal breathing movements?

Answer 7

Placental prostaglandin E2 (PGE2) prostacyclin (PGI2)

Question 8

What happens when you clamp the umbilical cord?

Answer 8

• Blood flow through the umbilical vein to the ductus venosus ceases and is now directed toward the portal system.
• Permanent fibrosis of umbilical vein at 1-2 weeks
• rise in systemic vascular resistance and BP
• increased pressure in LA

Question 9

What does the increase in LA pressure trigger?

Answer 9

closure of the foramen ovale closing R–>L shunt

Question 10

After birth, what causes the ductus arterioles to close?

Answer 10

Increases in BP and decreases in blood flow across the ductus arterioles along with increased PaO2 levels resulting in closure of the right to left shunt. It is permanently shut from 3weeks to 3 months after birth

Question 11

What happens to prostaglandin levels after birth?

Answer 11

decrease to nearly zero 5 years after birth

Question 12

What changes in the circulatory system after birth?

Answer 12

changes from a parallel circulation to a series circulation

Question 13

Why does fluid accumulate in the lunch of the fetus and what happens to this fluid after birth?

Answer 13

Fetal lungs secrete a fluid that stimulates alveoli growth. Prior to labor onset, fluid secretion diminishes potentially due to catecholamine release associated with labor. During during, fluid is expelled from the lungs as the baby passes through the vagina and creates a negative pressure that expels fluid from the babies lungs.

Question 14

What is likely to occur if the fetus does not experience vaginal labor?

Answer 14

develop transient tachypnea (TTN)

Question 15

What stimulates the lungs to become active at time of birth?

Answer 15

• hypoxia, hypercarbia, acidosis causes fetal aortic and carotid chemoreceptors to activate leading to activation of the respiratory center in the medulla
• temperature fall activates thermoreceptors in the skin to trigger respiratory center to start breathing
• vigorous dying causes tactile stimulation that causes you to start breathing

Question 16

How does crying facilitate the 1st breath?

Answer 16

creates a positive intrathoracic pressure keeping alveoli open

Question 17

What happens during the first breath?

Answer 17

1. PO2 increases and this causes pulmonary vasodilation
2. pulm artery smooth muscle cells relax due to NO and PG
3. pulm arterial resistance falls
4. plum blood flow increases to meet demands of increasing alveolar ventilation
5. pulm arterial blood pressure falls L heart pressure rises

Question 18

What are calcium levels in neonates?

Answer 18

low because PTH secretion is immature

Question 19

What are blood sugar readings in neonates?

Answer 19

very low because their hyperglycemic counter-regulatory mechanism is not working immediately after birth

Question 20

What type of thermogenesis does the fetus and neonatal experience?

Answer 20

non-shivering thermogenesis initiated by the brown fat tissues which are stimulated in exposure to cold, oxygenation, catecholamine surge at birth, and withdrawal of placental PGE2.

Question 21

What is the first bowel movement called?

Answer 21

meconium-a dark green viscous substance that can be excreted in the first 48 hours

Question 22

How are levels of Vitamin K and bacteria in the intestine at birth?

Answer 22

Gut is not fully colonized at birth so babies are given a shot of Vitamin K to help them produce the vitamin-K dependent clotting factors (babies don’t have the bacteria necessary to help them absorb Vit K)

Question 23

What causes babies to become jaundiced at birth?

Answer 23

decreased glucurono-transformation of serum bilirubin

Question 24

How is renal function in the neonatal stage?

Answer 24

• Really low GFR that would correspond to end-stage renal failure.
• renal vascular resistance is very high while RBF is low allowing for effective filtration pressure in glomerulus.
• GFR doubles in the first 2 weeks.

Question 25

How is renal urinary functioning at birth?

Answer 25

• increased urinary loss of water and Na
• decreased urinary concentrating ability
• increased insensible water loss from skin

Question 26

How are the Apgar scores computed?

Answer 26

5 components scored from 1-5, taken in 5 minute intervals until scores greater than a 7. Each category is scored from 0-2.