hello. Welcome to HCM.
decresesd amniotic fluid
... known as oLIGOHYDROAMNIOS is a common condition. It may be harmless if detected late in pregnancy
. However, at 22 weeks you must ensure that, the renal status of the baby is normal. There are good TIFFA scans- I and Ii available these days to test the same.
Also, it is very important to be under regular monitoring of fluid levels as it is very very important for baby's nutrition. Also a very vigilant watch from mother's side for fetal movements is needed and any decrease in movement must be brought to notice of doctor.
from the dietary viewpoint, you can help best by drinking as much of water and healthy fluids like coconut water etc, for the entire remaining pregnancy.
There are some replenishing agents, particularly some essential acids which are available as sahets and have been told to increase fluid levels. You may discuss with a good obstetrician for them.
Hope this advice helps. Take care.