Final answer:
The true statement about human chorionic gonadotropin (hCG) is that higher-than-normal levels may indicate an ectopic pregnancy or Down syndrome. The hormone is essential for pregnancy maintenance and can be detected early after conception. Its levels peak around 10 weeks and do not uniformly increase throughout pregnancy.
Step-by-step explanation:
Among the statements provided regarding human chorionic gonadotropin (hCG), the true one is that higher-than-normal levels of hCG may indicate an ectopic pregnancy or Down syndrome. The hCG is a hormone produced by the cells of the chorion of the zygote and plays a crucial role in maintaining pregnancy. It can be detected in the blood and urine soon after implantation, which typically occurs about 6-12 days after fertilization. Levels of hCG can indeed be detected as early as a few weeks after conception, a fact utilizing which at-home pregnancy tests work. These tests determine the levels of hCG in urine.
hCG levels do not gradually and uniformly increase throughout pregnancy; they rise dramatically in the first trimester, peak around 10 weeks of gestation, and then generally decrease and level off for the remainder of the pregnancy. Significantly lower-than-normal increases in the levels of hCG may indicate a potential issue with the pregnancy, such as a miscarriage or blighted ovum, not necessarily a postdate pregnancy. Lastly, elevated levels of hCG do not confirm the presence of a tumor, and low levels do not exclude it, except in males who do not produce this hormone naturally.