Alpha-Fetoprotein and renal dysfunction of the fetus.

Alpha-fetoprotein (AFP) levels were measured in 25 pregnancies with renal dysfunction of the fetus. Oligohydramnios was found in 14 of 16 patients diagnosed by 20 weeks of gestation and in all of those diagnosed later. AFP levels in maternal serum were normal in 17 (68%), elevated in five (20%), and low in three patients (12%). AFP serum levels up to 24 weeks of gestation were significantly higher than after 24 weeks. AFP levels in amniotic fluid obtained from amniocentesis in six patients were normal or slightly elevated. We suggest that the concentration of AFP in amniotic fluid and maternal serum does not only depend on the physiologic proteinuria of the immature fetal kidneys but also on the permeability of the not yet keratinized fetal skin and the diluting volume of the amniotic fluid.