There are numerous reports on the duplication of the long arm of chromosome 3, ranging from 3ql2 to 3qter. Although the duplicated segments vary in size, a defined clinical phenotype, dup(3q) syndrome, has been investigated by us and others. A 22 year old G4P0030 (1SPAB, 2ELAB) Caucasian was referred at 31 weeks gestation for fetal anomalies on sonogram including hydrocephalus, bilateral polydactyly, and a possible CHD Amniocentesis was performed and showed an unbalanced chromosomal rearrangement: 46,XX,der(9)t(3;9) (q26.1;p24).ish. 46,XX,der(9)t(3;9)(q26.1;p24) (WCP3+WCP9+), and a positive acetylcholinesterase. Parental chromosomes showed that the father was a carrier of a balanced rearrangement: 46,XY,t(3;9) (q26.1;p24). The baby was bom at 42 weeks gestation following prostaglandin induction due to failure to progress. She weighed 4264 grains and cried spontaneously with APGAR scores of 8/8 at 1 and 5 minutes. The major dysmorphic features included: up-slanting palpebral fissures, synophyrs, prominent alveolar ridge, hypertelorism, down-turned corners of the mouth, short neck with redundant skin folds, bilateral postaxial polydactyly, a deep sacral dimple and an anteriorly displaced anus with low rectal stenosis. During the surgical correction of the rectal stenosis, a pre-sacral teratoma was excised. The telomeric DNA segment (9p24-pter) lost due to the translocation is generally associated with chromosomal capping rather than phenotypic expression. The clinical manifestations consistent with dup(3q) syndrome are being presented. To our knowledge, teratoma has not been described before as part of the dup3q phenotype.