What factor has the most significant influence on amniotic fluid levels?

Fetal urine production is the primary factor influencing amniotic fluid levels because it is the main source of amniotic fluid in the second and third trimesters of pregnancy. As the fetus develops, it produces urine, which contributes significantly to the volume of amniotic fluid. Under normal circumstances, the fetus excretes urine into the amniotic sac, and this is a continuous process that plays a crucial role in maintaining the appropriate volume of amniotic fluid.

While maternal hydration can affect amniotic fluid levels, its impact tends to be less pronounced compared to the substantial contribution from fetal urine production once the fetal kidneys are functioning. Maternal weight and medications can have various effects on maternal health and pregnancy outcomes, but they do not directly provide as significant an influence on the levels of amniotic fluid as fetal urine production does. Thus, fetal urine is the predominant contributor to amniotic fluid volume, making it the most significant factor in this regard.