__________ hormone levels found in the mother's blood and urine rise a lot during the first trimester, and it may play a part in the nausea and vomiting often linked to pregnancy.

Correct option is C

Human Chronic Gonadotropin (hCG) hormone levels rise rapidly in the first trimester of pregnancy and play a crucial role in maintaining the pregnancy. This hormone is responsible for triggering the production of progesterone and estrogen. Elevated hCG levels are often associated with the nausea and vomiting experienced during early pregnancy, commonly referred to as "morning sickness."
Explanation of each option:
· (a) Oestrogen – Incorrect. Oestrogen levels also rise during pregnancy but are not as directly related to nausea and vomiting as hCG is.
· (b) Progesterone – Incorrect. Progesterone is essential for maintaining pregnancy but does not directly cause the nausea associated with early pregnancy.
· (c) Human Chronic Gonadotropin hormone – Correct. This hormone's levels increase significantly during the first trimester, and it is linked to the nausea and vomiting experienced by many pregnant women.
· (d) Prolactin – Incorrect. Prolactin plays a role in milk production post-pregnancy, not in the early stages.