Developmental anomalies in a human fetus of 17 weeks' gestational age

Chromosome studies of a therapeutically aborted male fetus, after amniocentesis of a 41-year-old woman, showed an abnormal karyotype of 47, XY, + 18. The fetus had many of the external anomalies described in newborns with trisomy 18; macrodissection revealed many internal anomalies consistent with this syndrome. The external and internal findings are described.