Question

why does the brain increase the respiration rate and depth during pregnancy?
a to increase maternal blood oxygen levels
b to increase maternal blood carbon dioxide levels
c to decrease maternal blood carbon dioxide levels
d because the mother is breathing for two

Explanation:

During pregnancy, the body has increased metabolic demands. The fetus also produces carbon dioxide which is transferred to the maternal circulation. The brain increases respiration rate and depth to expel more carbon dioxide (as increased breathing helps remove more CO₂ from the blood). Option A is incorrect as oxygen levels in maternal blood are already near - saturation and not the main driver. Option B is wrong as we want to decrease CO₂. Option D is a bit of a misnomer; it's more about the physiological need to manage gas exchange (especially CO₂ removal) rather than a simple "breathing for two" concept in terms of the direct mechanism of respiratory rate and depth increase.

Answer:

C. To decrease maternal blood carbon dioxide levels