Fetal to Neonatal Transition Flashcards
What are the 3 phase of fetal to neonatal transitioning?
- Late gestation
- Parturition
- establishing independent homeostatic regulation after separation from the placenta
What happens to cortisol levels in the last 5 weeks of gestation?
increased cortisol contributing to lung maturation and surfactant production
What factors play a huge role in the final steps of parturition?
Prostaglandin F2 and Placental corticotropin-releasing factor that stimulates paracrine production of prostanoids from the fetal placental membranes to induce parturition.
What does the foramen ovale, ductus venous, and ductus arteriosus bypass?
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
What carries oxygenated blood from the parent to the fetus?
umbilical vein
How are nutrients transferred from the mother to the placenta?
glucose: carrier mediated diffusion
Proteins: rapid, slow and de novo synthesis
Fat: gradient dependent diffusion
What maintains an open ductus arteriosus, inhibits brown fat thermogenesis, and inhibits fetal breathing movements?
Placental prostaglandin E2 (PGE2) prostacyclin (PGI2)
What happens when you clamp the umbilical cord?
- 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
What does the increase in LA pressure trigger?
closure of the foramen ovale closing R–>L shunt
After birth, what causes the ductus arterioles to close?
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
What happens to prostaglandin levels after birth?
decrease to nearly zero 5 years after birth
What changes in the circulatory system after birth?
changes from a parallel circulation to a series circulation
Why does fluid accumulate in the lunch of the fetus and what happens to this fluid after birth?
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.
What is likely to occur if the fetus does not experience vaginal labor?
develop transient tachypnea (TTN)
What stimulates the lungs to become active at time of birth?
- 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
How does crying facilitate the 1st breath?
creates a positive intrathoracic pressure keeping alveoli open
What happens during the first breath?
- PO2 increases and this causes pulmonary vasodilation
- pulm artery smooth muscle cells relax due to NO and PG
- pulm arterial resistance falls
- plum blood flow increases to meet demands of increasing alveolar ventilation
- pulm arterial blood pressure falls L heart pressure rises
What are calcium levels in neonates?
low because PTH secretion is immature
What are blood sugar readings in neonates?
very low because their hyperglycemic counter-regulatory mechanism is not working immediately after birth
What type of thermogenesis does the fetus and neonatal experience?
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.
What is the first bowel movement called?
meconium-a dark green viscous substance that can be excreted in the first 48 hours
How are levels of Vitamin K and bacteria in the intestine at birth?
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)
What causes babies to become jaundiced at birth?
decreased glucurono-transformation of serum bilirubin
How is renal function in the neonatal stage?
- 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.
