Suggest Treatment And Symptoms Of Polyhydramnios

I am 40 yrs old, 31 weeks pregnant with 4th baby. Just found out yesterday I have this condition polyhydramnios? What could be possible causes? My first sugar test (1 hour was high) so I went to the 3-hour, then it came out normal. My amnio test also came out normal. Is there connection with taking coffee - just a cup a day (not really a coffee drinker, only this pregnancy I got addicted to coffee). ?