Second trimester amniotic fluid placental alkaline phosphatase levels are low in Down's syndrome but not in other fetal abnormalities.
Second trimester amniotic fluid placental alkaline phosphatase (PLAP) immunoreactivity was measured in 756 normal pregnancies, 63 Down's syndrome pregnancies and 42 pregnancies associated with other chromosomal abnormalities. PLAP levels were significantly reduced in cases of Down's syndrome (MoM = 0.72, U = 17,565, P = 0.0002, 95% Cl = 0.63-0.88). However, there was no significant difference between other aneuploid conditions and the normals (MoM = 0.88, U = 13,289, P = 0.35, 95% CI = 0.77-1.08). PLAP is the carrier protein for immunoglobulin G. Neonates with Downs syndrome but not other chromosomal abnormalities are associated with a deficiency of IgG. These data therefore support the theory that the low IgG levels in Downs syndrome are a result of a defect in PLAP transport.
Department of Reproductive Physiology, St Bartholomew's Hospital, West Smithfield, London, UK.
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Wathen
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Carvalho
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Campbell
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D000469:Alkaline Phosphatase / Q000378:metabolism*; D000653:Amniotic Fluid / Q000201:enzymology*; D002869:Chromosome Aberrations / Q000196:embryology; D025063:Chromosome Disorders; D004314:Down Syndrome / Q000196:embryology / Q000201:enzymology*; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second
D000469:Alkaline Phosphatase