The nurse is interviewing a client who is pregnant in her first trimester, and the client inquires about their gestational age. The nurse understands which assessment will provide the most accurate gestational age?

Choice A rationaleUltrasonography provides the most accurate assessment of gestational age, especially in the first trimester, by measuring the crown-rump length.Choice B rationaleHCG levels can indicate pregnancy but are not as accurate for determining the exact gestational age.Choice C rationaleNagele's rule is based on the menstrual cycle and may not be accurate if cycles are irregular.Choice D rationaleFundal height measurement is less accurate in early pregnancy and more useful in later trimesters.