Can the size of the gestational sac determine how long the pregnancy has been?

Patient's question:

No

Doctor's answer:

This can give a general idea, but not a very clear understanding. The usual method is to use ultrasound to observe the fetal development in terms of body shape and condition to get a general overview. However, there can be individual differences, such as nutrition and rest conditions, which can be quite significant. Additionally, hormonal levels should be considered.