What factor has the least influence on amniotic fluid levels?

The factor that has the least influence on amniotic fluid levels is maternal weight. Amniotic fluid volume is primarily determined by fetal urine production and the balance between fetal swallowing and the transfer of fluids through the fetal lungs.

While maternal hydration status can significantly impact amniotic fluid levels—dehydration can reduce blood flow to the placenta and subsequently affect fetal urine output—maternal weight does not have a direct or strong effect on the dynamics of amniotic fluid production or maintenance.

Fetal urine production, on the other hand, is a major contributor to amniotic fluid as the fetus begins to urinate into the amniotic sac, which increases fluid volume. The lungs also contribute to the fluid dynamics through the production of lung fluid, especially in later gestation. Therefore, maternal weight has a lesser impact compared to these other physiological factors on amniotic fluid levels.