Transition from Intrauterine to Extrauterine Life

Question 1

Describe the adaptation of the fetal respiratory system at the time of birth. How does this occur?

Answer 1

• The lungs need to be cleared of fluid. fast.
• To do this:
  (1) respiratory epithelium changes from secretory to absorptive, drawing fluid in (sodium mediated)
  (2) labour contractions help expel fluid from lungs
  (3) Inspiration increases trans-epithelial pressure gradient, pushes fluid into lung tissue

Question 2

Describe circulatory changes that occur in the fetus at the time of birth

Answer 2

• Umbilical vessels clamped off (or, otherwise, wharton’s jelly swells and closes them after ~20mins)
• Foramen ovale closes due to increase LA pressure
• DA closes off due to increased O2 and decreased PGs
• DV degenerates, and becomes ligamentum venosum

Question 3

What metabolic changes occur as we transition to ex utero life?

Answer 3

• Transition from anaerobic to aerobic metabolism
• Increase in glucose levels to provide energy needed for this

Question 4

Endocrine changes in transition to ex utero

Answer 4

• Increased stress hormones (adrenaline + cortisol)
• Increased thyroid hormones, crucial for growth and development

Question 5

Haematologic changes in transition to ex utero (incl haemoglobin chain composition)

Answer 5

• Switch from HbF (2 alpha 2 gamma) to HbA (2 alpha 2 beta)
• Increased RBC production (in response to ↑ demand)