Which sequence describes transitional circulation in newborns?

The correct answer details the process of transitional circulation in newborns, which begins with the initiation of breathing after birth. Once the baby takes its first breath, air enters the lungs, leading to the expansion of alveoli and increased blood flow to the lungs. As a result, gas exchange occurs, allowing oxygen to be absorbed into the bloodstream and carbon dioxide to be expelled. This significant increase in oxygen saturation is crucial for the newborn as it supports vital organ function and reduces reliance on fetal circulation.

By understanding this sequence, it is evident why this answer aligns with the physiological changes that take place during the transition from fetal to neonatal life. Each step builds upon the previous one, demonstrating the importance of breathing in facilitating the transition to effective pulmonary circulation.

The other choices do not accurately reflect this process. Option B introduces heart rate increases alongside gas exchange but incorrectly mentions oxygen deficiency instead of highlighting the rise in oxygen saturation that occurs due to effective lung function. Option C describes blood movement to the left atrium and an increase in pulmonary resistance, which misrepresents the physiological response as effective transition involves decreased pulmonary resistance. Lastly, option D suggests that gas exchange fails and leads to a decrease in heart rate, which is not characteristic of a successful transition and does not reflect