Many things. Oligohydramnios (low fluid levels) can imply possible leakage or poor production from the fetus which can imply poor growth or kidney or other organ being compromised. Amniotic fluid is natural fluid from the fetus (urine). Polyhydramnios (too much fluid) can imply potential congenital anomaly or it can also be "normal." fluid levels help doctors determine whether further investigation is required.