The many causes of a reduction in amniotic fluid are highly variable.
One major cause of a decrease in amniotic fluid is the mother’s diet and lifestyle habits (smoking, excess caffeine and alcohol consumption, diets high in processed foods). Unhealthy weight gain or very restrictive eating habits can also contribute to low levels. Leakage of fluids could also be a likely cause.
Monitoring the intake, output and swelling of your ankles will help to identify signs that you are urinating or retaining fluid. Drink more fluids, avoid salty foods and medications that promote sodium retention.
Be sure to drink lots of water and eat foods high in fiber and sodium so you produce more amniotic fluid naturally! Do see a doc to check for leakage too.