Routine maternal serum alpha-fetoprotein measurement in 210 pregnancies

Of 210 maternal serum samples none had alpha-fetoprotein (AFP) level above the mean and 22 (10.4%) had a level under the mean; of these, 21 had maternal serum AFP levels within normal limits upon repeat sampling within 1-2 weeks of the original evaluation. When low AFP values are interpreted in order to identify women at risk of carrying a fetus with Down's syndrome, obstetricians should be aware of high incidence of false positive at the first assay.