Passage of mannitol from mother to amniotic fluid and fetus.

Ten pregnant women and three pregnant sheep received mannitol intravenously. The results show that during late pregnancy this substance appears in amniotic fluid, and when the fetus is alive, its concentration increases with time, reaching values which are higher than those simultaneously obtained in maternal plasma. The experiments performed in sheep show that in fetal urine the concentration of mannitol reached values 10 to 20 times higher than those found in fetal plasma. This supports the hypothesis that the fetal kidney has an important role in the transference of this type of substance from the mother to the amniotic fluid.