We report on 2 couples at risk to have Meckel syndrome (MS) offspring. Three pregnancies were monitored by ultrasonography and alpha-fetoprotein (AFP) assay in midtrimester. Of the 2 involving an affected fetus, one was thought to be unaffected. A literature survey was undertaken. Sources of error seem to lie in the heterogeneity of clinical manifestations and the variable onset and rate of progression of clinical components of MS and limitations in ultrasonographic resolution inherent in the scanner or due to the associated oligohydramnios. The following observations/suggestions are made concerning the prenatal diagnosis of MS: 1) Utilize as many tests as are available. 2) Amniotic fluid AFP is more likely to show significant elevation than serum AFP. 3) Ultrasonography should concentrate on presence of oligohydramnios, small head diameter, cystic mass at the occiput, large kidneys, and absent bladder. 4) Use serial AFP and sonographic examination if findings are initially normal or equivocal.