α-Fetoprotein and the Prenatal Diagnosis of Central Nervous System Disorders

Abstract

The use of amniotic fluid α-fetoprotein measurements in the early prenatal diagnosis of central nervous system disorders is reviewed. The method is sensitive and specific and has had a pronounced effect on the counselling of mothers who have already had a child with spina bifida or anencephaly. Measurement of other amniotic fluid components, such as fetal macrophages, β-trace protein, α₂-macroglobulin or fibrinogen-degradation products, is less reliable and these should not be used in making primary diagnoses. The assay of α-fetoprotein in maternal serum shows signs of being a useful preliminary screening process, and may identify pregnancies where amniocentesis and confirmatory amniotic fluid determinations should be offered.

Raised alpha-fetoprotein levels in amniotic fluid and maternal serum associated with distension of the fetal bladder caused by absence of urethra.

“…This hypothesis is supported by the findings of high AFP levels in fetal serum and fetal cerebrospinal fluid between 15 and 20 weeks' gestation and also by normal amniotic AFP levels in fetal neural tube defects covered by a full thickness of skin (Brock, 1976). It has also been suggested that the raised amniotic fluid AFP may be the result of fetal serum transudation rather than a leakage into the amniotic fluid (Weiss et al, 1976).…”

“…At necropsy, the abdominal distension which has persisted even after decompression resulted from an enormously enlarged bladder into which one (the left) dilated ureter entered (Fig. 2) (Brock, 1976). It has also been suggested that the raised amniotic fluid AFP may be the result of fetal serum transudation rather than a leakage into the amniotic fluid (Weiss et al, 1976).…”