Mechanisms by which amniotic-fluid alpha-fetoprotein may be increased in fetal abnormalities.
Assuming that urination is the principle route by which alpha-fetoprotein (A.F.P.) passes into the amniotic fluid from the normal fetus, and that A.F.P. is mainly degraded by a process of fetal swallowing and digestion, 4 possible mechanisms by which amniotic-fluid A.F.P. is increased by fetal abnormalities are postulated.(1) Amniotic-fluid A.F.P. is increased in open neural-tube defects by leakage of A.F.P. from fetal serum and cerebrospinal fluid.(2) In exomphalos exposure of blood-vessels in the extruding viscera permits transudation of A.F.P. into the amniotic fluid.(3) In nephrosis, fetal proteinuria increases amniotic-fluid A.F.P.(4) Impaired fetal swallowing or digestion would account for increased amniotic-fluid A.F.P. in congenital malformations of the orogastrointestinal tract.
D000653:Amniotic Fluid / Q000378:metabolism*; D000757:Anencephaly / Q000378:metabolism; D000013:Congenital Abnormalities / Q000378:metabolism; D003680:Deglutition Disorders / Q000151:congenital / Q000378:metabolism; D004063:Digestion; D004386:Duodenum / Q000002:abnormalities; D004933:Esophageal Atresia / Q000378:metabolism; D005260:Female; D005315:Fetal Diseases / Q000378:metabolism*; D005326:Fetal Proteins / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism*; D006554:Hernia, Umbilical / Q000151:congenital / Q000378:metabolism; D006801:Humans; D009401:Nephrosis / Q000151:congenital / Q000378:metabolism; D011247:Pregnancy; D011507:Proteinuria / Q000151:congenital / Q000378:metabolism; D016135:Spinal Dysraphism / Q000378:metabolism; D000509:alpha-Fetoproteins / Q000378:metabolism*
D005326:Fetal Proteins; D000509:alpha-Fetoproteins