pocket of fluid under the skin on her lower stomach 38wks

my girlfriend is pregnant and has a pocket of fluid under the skin on her lower stomach why is this and what is the cause and what are the complications? does anyone have this or have heard of it i am very worried. and when we went to the doctors they didnt give and reasons as to why or anything that could result from it, they did however mention it was outside the utereus. she is over 38 weeks now and this close to her due date i am afraid of complications.