Implications of 'low' maternal serum alpha-fetoprotein levels: are maternal age risk criteria obsolete?

An association has been reported between 'low' maternal serum alpha-fetoprotein (MSAFP) and fetal chromosome abnormalities, notably Down syndrome. We suggest the predictive value be used for genetic counselling when a 'low' MSAFP is found, and present an illustrative risk table. It can also be seen that normal MSAFP in a woman may lower her age-related risks below that previously defined as 'high risk'. However, until good estimates of sensitivity and specificity are available from prospective, population based studies, patients should be told that any risk estimates are rough approximations. When good estimates are available, use of age risks alone may become obsolete.