What is the difference between amniotic index and amniotic depth?

Patient's question:

No

Doctor's answer:

The maximum vertical amniotic fluid depth between 3-7 cm is normal, exceeding 7 cm indicates polyhydramnios, and less than 3 cm indicates oligohydramnios. Centered on the's umbilicus, the four regions (upper, lower, left, right) are divided. The sum of the amniotic fluid depths in these four regions gives the amniotic fluid index. The normal value of the amniotic fluid index in the late pregnancy is 8-20.