Sacrococcygeal teratoma: prenatal diagnosis with elevated alphafetoprotein and acetylcholinesterase in amniotic fluid.

A sacrococcygeal teratoma was suspected by ultrasound examination at 24 weeks gestation. The amniotic fluid alphafetoprotein was markedly elevated, as was maternal serum AFP. Gel electrophoresis of amniotic fluid showed an acetylcholinesterase band. Labour began at 25 weeks gestation and the chromosomally normal male fetus was found to have a sacrococcygeal teratoma equal to three-quarters of the weight of the fetus.